Geografic-Information-System/lib/gis/gisrasterlib.dox

/*! \page gisrasterlib Raster File Processing
<!-- doxygenized from "GRASS 5 Programmer's Manual" 
     by M. Neteler 2/2004, 8/2005, 2006
  -->

\section gisrastintro GRASS Raster File Processing

<P>
<B>TODO: this sections needs to be cleaned up. The upper GRASS 4.x
 and the lower GRASS 5.x/6.x parts need to me merged.
 </B>

- \subpage gisrastintro
- \subpage Opening_an_Existing_Raster_File
- \subpage Creating_and_Opening_New_Raster_Files
- \subpage Allocating_Raster_I_O_Buffers
- \subpage Reading_Raster_Files
- \subpage Raster_Map_Layer_Support_Routines
- \subpage Raster_Header_File
- \subpage Raster_Category_File
- \subpage Reading_and_Writing_the_Raster_Category_File
- \subpage Querying_and_Changing_the_Categories_Structure
- \subpage Raster_Color_Table
- \subpage Reading_and_Writing_the_Raster_Color_File
- \subpage Lookup_Up_Raster_Colors
- \subpage Creating_and_or_Modifying_the_Color_Table
- \subpage Predefined_Color_Tables
- \subpage Raster_History_File
- \subpage Raster_Range_File
- \subpage Raster_Histograms
- \subpage GRASS_5_raster_API
- \subpage Upgrades_to_Raster_Functions
- \subpage Null_no_data
- \subpage Color_Functions
- \subpage New_functions_to_support_colors_for_floating_point
- \subpage New_functions_to_support_a_colors_for_the_NULL_value
- \subpage New_functions_to_support_a_default_color
- \subpage New_functions_to_support_treating_a_raster_layer_as_a_color_image
- \subpage Upgraded_color_functions
- \subpage Changes_to_the_Colors_structure
- \subpage Changes_to_the_colr_file
- \subpage Range_functions
- \subpage New_range_functions
- \subpage New_and_Upgraded_Cell_stats_functions
- \subpage New_Quantization_Functions
- \subpage Categories_Labeling_Functions
- \subpage Changes_to_the_cats_file
- \subpage Range_functions
- \subpage New_Functions_to_read_write_access_and_modify_Categories_structure
- \subpage Library_Functions_that_are_Deprecated
- \subpage Guidelines_for_upgrading_GRASS_4_x_Modules
- \subpage Important_hints_for_upgrades_to_raster_modules

<P>
Raster files are the heart and soul of GRASS (update 2005: meanwhile also
vector data processing entered GRASS' heart).  Because of this, a
suite of routines which process raster file data has been
provided. The processing of raster files consists of determining which
raster file or files are to be processed (either by prompting the user
or as specified on the module command line), locating the raster file
in the database, opening the raster file, dynamically allocating i/o
buffers, reading or writing the raster file, closing the raster file,
and creating support files for newly created raster files.

<P>
Raster file data can be of type CELL, FCELL or DCELL, they are defined
in "gis.h". CELL is a 32-bit signed integer, FCELL is an IEEE single-precision
floating-point, and  DCELL is an IEEE double-precision floating-point.
G3D (GRID3D) is treated as DCELL.
<P>

Prompting for Raster Files</A>


<P>
The following routines interactively prompt the user for a raster file
name.  In each, the <B>prompt</B> string will be printed as the first
line of the full prompt which asks the user to enter a raster file
name. If <B>prompt</B> is the empty string "" then an appropriate
prompt will be substituted. The name that the user enters is copied
into the <B>name</B> buffer (The size of name should be large enough
to hold any GRASS file name. Most systems allow file names to be quite
long. It is recommended that name be declared char name.)  These
routines have a built-in 'list' capability which allows the user to
get a list of existing raster files.

<P> The user is required to enter a valid raster file name, or else
hit the RETURN key to cancel the request. If the user enters an
invalid response, a message is printed, and the user is prompted
again. If the user cancels the request, the NULL pointer is
returned. Otherwise the mapset where the raster file lives or is to be
created is returned. Both the name and the mapset are used in other
routines to refer to the raster file.

<P>
char * G_ask_cell_old(char *prompt, char *name) prompt for existing
raster file

Asks the user to enter the name of an existing raster file in any
mapset in the database.

<P> char * G_ask_cell_in_mapset(char *prompt, char *name) prompt for
existing raster file

Asks the user to enter the name of an existing raster file in the
current mapset.

<P> char * G_ask_cell_new(char *prompt, char *name) prompt for new
  raster file

Asks the user to enter a name for a raster file which does not exist
in the current mapset.

<P> Here is an example of how to use these routines. Note that the
programmer must handle the NULL return properly:


\verbatim
char *mapset;
char name[GNAME_MAX];

mapset = G_ask_cell_old("Enter raster file to be processed", name);

if (mapset == NULL)
  return(0);
\endverbatim


\subsection Finding_Raster_Files_in_the_Database Finding Raster Files
in the Database

<P>
Noninteractive modules cannot make use of the interactive prompting
routines described above. For example, a command line driven module
may require a raster file name as one of the command arguments. GRASS
allows the user to specify raster file names (or any other database
file) either as a simple unqualified name, such as "soils", or as a
fully qualified name, such as "soils@<I>mapset</I>", where
<I>mapset</I> is the mapset where the raster file is to be
found. Often only the unqualified raster file name is provided on the
command line.

<P>
The following routines search the database for raster files:

<P>
char * G_find_cell(char *name, char *mapset) find a raster file

Looks for the raster file <B>name</B> in the database. The
<B>mapset</B> parameter can either be the empty string "", which means
search all the mapsets in the user's current mapset search path, or it
can be a specific mapset name, which means look for the raster file
only in this one mapset (for example, in the current mapset) . If
found, the mapset where the raster file lives is returned. If not
found, the NULL pointer is returned.

<P>
If the user specifies a fully qualified raster file which exists, then
<I>G_find_cell() </I> modifies <B>name</B> by removing the
"@<I>mapset</I>".

<P>
For example, to find a raster file anywhere in the database:

\verbatim
char name[GNAME_MAX];
char *mapset;

if ((mapset = G_find_cell(name,"")) == NULL)
  /* not found */
\endverbatim


<P>
To check that the raster file exists in the current mapset:

\verbatim
char name[GNAME_MAX];

if (G_find_cell(name,G_mapset()) == NULL)
  /* not found */
\endverbatim


<P>

\section Opening_an_Existing_Raster_File Opening an Existing Raster File


<P>
The following routine opens the raster file <B>name</B> in <B>mapset</B> for
reading.

<P>
The raster file <B>name</B> and <B>mapset</B> can be obtained
interactively using <I>G_ask_cell_old()</I> or <I>
G_ask_cell_in_mapset()</I>, and noninteractively using <I>
G_find_cell()</I>.

<P>
int G_open_cell_old(char *name, char *mapset) open an existing
  raster file

This routine opens the raster file <B>name</B> in <B>mapset</B> for
reading. A nonnegative file descriptor is returned if the open is
successful. Otherwise a diagnostic message is printed and a negative
value is returned. This routine does quite a bit of work. Since GRASS
users expect that all raster files will be resampled into the current
region, the resampling index for the raster file is prepared by this
routine after the file is opened. The resampling is based on the
active module region. Preparation required for reading the various
raster file formats is also done.

<P>

\section Creating_and_Opening_New_Raster_Files Creating and Opening New Raster Files

####################
<P>
The following routines create the new raster file <B>name</B> in the
current mapset [footnote] and open
it for writing. The raster file <B>name</B> should be obtained
interactively using <I>G_ask_cell_new.</I> If obtained
noninteractively (e.g., from the command line) ,
<I>G_legal_filename</I> should be called first to make sure that
<B>name</B> is a valid GRASS file name.

<P>
<B>Note.</B> It is not an error for <B>name</B> to already exist. New 
raster files are actually created as temporary files and moved into the cell 
directory when closed. This allows an existing raster file to be read at the 
same time that it is being rewritten. The interactive routine 
<I>G_ask_cell_new</I> guarantees that <B>name</B> will not exist, but 
if <B>name</B> is obtained from the command line, <B>name</B> may exist. 
In this case <I>G_find_cell</I> could be used to see if <B>name</B> exists.

<P>
<B>Warning.</B> However, there is a subtle trap. The temporary file, which 
is created using <I>G_tempfile</I>, is named using the current process 
id. If the new raster file is opened by a parent process which exits after 
creating a child process using fork(), [footnote] 
the raster file may never get created since the temporary file 
would be associated with the parent process, not the child. GRASS management 
automatically removes temporary files associated with processes that are no 
longer running. If fork() must be used, the safest course of action is to 
create the child first, then open the raster file. (See the discussion under 
<I>G_tempfile()</I> for more details.) 

<P>
FILE * G_open_cell_new(char *name) open a new raster file
  (sequential) Creates and opens the raster file <B>name</B> for writing by
  <I>G_put_map_row</I> which writes the file row by row in sequential
  order. The raster file data will be compressed as it is written.

<P>
A nonnegative file descriptor is returned if the open is successful.
  Otherwise a diagnostic message is printed and a negative value is returned.

<P>
FILE * G_open_cell_new_random(char *name) open a new raster file
  (random) Creates and opens the raster file <B>name</B> for writing by
  <I>G_put_map_row_random</I> which allows writing the raster file in a
  random fashion. The file will be created uncompressed. [footnote]
<P>
A nonnegative file descriptor is returned if the open is successful.
  Otherwise a diagnostic message is printed and a negative value is returned.

<P>
FILE * G_open_cell_new_uncompressed(char *nameopen a new raster
  file (uncompressed) Creates and opens the raster file <B>name</B> for
  writing by <I>G_put_map_row</I> which writes the file row by row in
  sequential order. The raster file will be in uncompressed format when closed.

<P>
A nonnegative file descriptor is returned if the open is successful.
  Otherwise a warning message is printed on stderr and a negative value is
  returned.

<P>
General use of this routine is not recommended. [footnote]
 This routine is provided so the
  <I>r.compress module</I> can create uncompressed raster files.  

<P>

\section Allocating_Raster_I_O_Buffers Allocating Raster I/O Buffers


<P>
Since there is no predefined limit for the number of columns in the
region,[footnote] 
 buffers which are used for reading and writing raster data must be
dynamically allocated.

<P>
CELL * G_allocate_cell_buf(void) allocate a raster buffer This
  routine allocates a buffer of type CELL just large enough to hold one row of
  raster data (based on the number of columns in the active region).

 
\verbatim
CELL *cell;
cell = G_allocate_cell_buf(void) ;
\endverbatim

<P>
If larger buffers are required, the routine <I>G_malloc</I> can be used.

<P>
If sufficient memory is not available, an error message is printed and exit() 
is called.

<P>
int G_zero_cell_buf(CELL *buf) zero a raster buffer This
  routines assigns each member of the raster buffer array <B>buf</B> to zero.
  It assumes that <B>buf</B> has been allocated using
  <I>G_allocate_cell_buf.</I>

<P>

\section Reading_Raster_Files Reading Raster Files

Needs updating for GRASS 5!! See later in this file.
<BR>
<P>
Raster data can be thought of as a two-dimensional matrix. The routines
described below read one full row of the matrix. It should be understood,
however, that the number of rows and columns in the matrix is determined by the
region, not the raster file itself. Raster data is always read resampled into
the region. [footnote]
This allows the user to specify the coverage of
the database during analyses. It also allows databases to consist of raster
files which do not cover exactly the same area, or do not have the same grid
cell resolution. When raster files are resampled into the region, they all
"look" the same.

<P>
<B>Note.</B> The rows and columns are specified "C style", i.e., 
starting with 0.

<P>

<P><P>
<BR>
THIS FUNCTION IS DEPRECATED IN GRASS 5! SEE NEXT CHAPTER!

<P>
int G_get_map_row (int fd, CELL *cell, int row) read a raster file
This routine reads the specified <B>row</B> from the raster file open on
  file descriptor <B>fd</B> (as returned by <I>G_open_cell_old</I>) into
  the <B>cell</B> buffer. The <B>cell</B> buffer must be dynamically
  allocated large enough to hold one full row of raster data. It can be
  <I>allocated using G_allocate_cell_buf.</I>

<P>
This routine prints a diagnostic message and returns -1 if there is an error
  reading the raster file. Otherwise a nonnegative value is returned.

<P>
int G_get_map_row_nomask (int fd, CELL *cell, int row) read a
  raster file (without masking) This routine reads the specified <B>row</B>
  from the raster file open on file descriptor <B>fd</B> into the
  <B>cell</B> buffer like G_get_map_row() does. The difference is that
  masking is suppressed. If the user has a mask set, G_get_map_row() will
  apply the mask but G_get_map_row_nomask() will ignore it.

<P>
This routine prints a diagnostic message and returns -1 if there is an error 
reading the raster file. Otherwise a nonnegative value is returned.

<P>
<B>Note.</B> Ignoring the mask is not generally acceptable. Users expect 
the mask to be applied. However, in some cases ignoring the mask is 
justified. For example, the GRASS modules <I>r.describe</I>, which reads 
the raster file directly to report all data values in a raster file, and 
<I>r.slope.aspect</I>, which produces slope and aspect from elevation, 
ignore both the mask and the region. However, the number of GRASS modules 
which do this should be minimal. See Mask for more information 
about the mask.

<P>

\subsection Writing_Raster_Files Writing Raster Files

Needs updating for GRASS 5!! See later in this file.
<BR>
<P>
The routines described here write raster file data.

<P>
int G_put_map_row (int fd, CELL *buf) write a raster file
  (sequential) This routine writes one row of raster data from <B>buf</B> to
  the raster file open on file descriptor <B>fd.</B> The raster file must
  have been opened with <I>G_open_cell_new.</I>

<P>
The cell <B>buf</B> must have been allocated large enough for the region,
  perhaps using <I>G_allocate_cell_buf.</I>

<P>
If there is an error writing the raster file, a warning message is printed
  and -1 is returned. Otherwise 1 is returned.

<P>
<B>Note.</B> The rows are written in sequential order. The first call
  writes row 0, the second writes row 1, etc. The following example assumes
  that the raster file <B>name</B> is to be created:

<P>
\verbatim
int fd, row, nrows, ncols;

CELL *buf;

fd = G_ope... /*...data for the row */

G_put_map_row(fd, buf) ;
\endverbatim

<P>
int G_put_map_row_random (int fd, CELL *buf, int row, int col, int
  ncells) write a raster file (random) This routine allows random writes to
  the raster file open on file descriptor <B>fd.</B> The raster file must
  have been opened using <I>G_open_cell_new_random.</I> The raster buffer
  <B>buf</B> contains <B>ncells</B> columns of data and is to be written
  into the raster file at the specified <B>row</B>, starting at column
  <B>col.</B>

<P>

\subsection Closing_Raster_Files Closing Raster Files


<P>
All raster files are closed by one of the following routines, whether opened 
for reading or for writing.

<P>
int G_close_cell (int fd) close a raster file The raster file
  opened on file descriptor <B>fd</B> is closed. Memory allocated for raster
  processing is freed. If open for writing, skeletal support files for the new
  raster file are created as well.

<P>
<B>Note.</B> If a module wants to explicitly write support files (e.g., a
  specific color table) for a raster file it creates, it must do so after the
  raster file is closed. Otherwise the close will overwrite the support files.
  See \ref Raster_Map_Layer_Support_Routines for routines which write
  raster support files.

<P>
int G_unopen_cell (int fd) unopen a raster file The raster file
  opened on file descriptor <B>fd</B> is closed. Memory allocated for raster
  processing is freed. If open for writing, the raster file is not created and
  the temporary file created when the raster file was opened is removed (see
  Creating_and_Opening_New_Raster_Files) .

<P>
This routine is useful when errors are detected and it is desired to not
  create the new raster file. While it is true that the raster file will not be
  created if the module exits without closing the file, the temporary file will
  not be removed at module exit. GRASS database management will eventually
  remove the temporary file, but the file can be quite large and will take up
  disk space until GRASS does remove it. Use this routine as a courtesy to the
  user.  

<P>

\section Raster_Map_Layer_Support_Routines Raster Map Layer Support Routines


<P>
GRASS map layers have a number of support files associated with them. These 
files are discussed in detail in Raster_Maps. The support files 
are the <I>raster header</I>, the <I>category</I> file, the 
<I>color</I> table, the <I>history</I> file, and the <I>range</I> file. 
Each support file has its own data structure and associated routines.

<P>

\section Raster_Header_File Raster Header File


<P>
The raster header file contains information describing the geographic extent 
of the map layer, the grid cell resolution, and the format used to store the 
data in the raster file. The format of this file is described in
Raster_Header_Format. The routines described below use the 
<I>Cell_head</I> structure which is shown in detail in
GIS_Library_Data_Structures.

<P>
int G_get_cellhd(char *name, char *mapset, struct Cell_Head
  *cellhd) read the raster headerThe raster header for the raster file
  <B>name</B> in the specified <B>mapset</B> is read into the
  <B>cellhd</B> structure.

<P>
If there is an error reading the raster header file, a diagnostic message is 
printed and -1 is returned. Otherwise, 0 is returned.

<P>
<B>Note.</B> If the raster file is a reclass file, the raster header for 
the referenced raster file is read instead. See \ref Reclass_Format for 
information about reclass files, and  <I>G_is_reclass</I> for 
distinguishing reclass files from regular raster files.

<P>
<B>Note.</B> It is not necessary to get the raster header for a map layer in
order to read the raster file data. The routines which read raster file data
automatically retrieve the raster header information and use it for resampling
the raster file data into the active region. [footnote] 
If it is necessary to read the raster file directly
without resampling into the active region, [footnote]
then the raster header can be used to set the active region using
<I>G_set_window.</I>

<P>
char * G_adjust_Cell_head(struct Cell_Head *cellhd, int rflag, int
  cflag) adjust cell headerThis function fills in missing parts of the input
  cell header (or region) .  It also makes projection-specific adjustments. The
  <B>cellhd</B> structure must have its <I>north, south, east, west</I>,
  and <I>proj</I> fields set. If <B>rflag</B> is true, then the north-south
  resolution is computed from the number of <I>rows</I> in the
  <B>cellhd</B> structure. Otherwise the number of <I>rows</I> is computed
  from the north-south resolution in the structure, similarly for
  <B>cflag</B> and the number of columns and the east-west resolution. This
  routine returns NULL if execution occurs without error, otherwise it returns
  an error message.

<P>
char * G_put_cellhd(char *name, struct Cell_Head *cellhd) write
  the raster header This routine writes the information from the
  <B>cellhd</B> structure to the raster header file for the map layer
  <B>name</B> in the current mapset.

<P>
If there was an error creating the raster header, -1 is returned. No 
diagnostic is printed. Otherwise, 1 is returned to indicate success.

<P>
<B>Note.</B> Programmers should have no reason to use this routine. It is 
used by <I>G_close_cell</I> to giv e new raster files correct header 
files, and by the <I>r.support module</I> to give users a means of 
creating or modifying raster headers. 

<P>
int G_is_reclass(char *name, char *mapset, char r_name, char
**r_mapset) reclass file?This function determines if the raster file
*<B>name</B> in <B>mapset</B> is a reclass file.
If it is, then the name and mapset of the referenced 
raster file are copied into the <B>r_name</B> and <B>r_mapset</B> 
buffers.

<P>
Returns 1 if <B>name</B> is a reclass file, 0 if it is not, and -1 if 
there was a problem reading the raster header for <B>name.</B>

<P>
int G_is_reclassed_to(char *name, char *mapset, int *nrmaps, 
char ***rmaps) get child reclass maps listThis function generates a
child reclass maps list from the cell_misc/reclassed_to file which stores 
this list. The cell_misc/reclassed_to file is written by 
G_put_reclass() .

<P>
G_is_reclassed_to() is used by g.rename, g.remove and r.reclass to
prevent accidentally deleting the parent map of a reclassed raster map.

<P>

\section Raster_Category_File Raster Category File


<P>
GRASS map layers have category labels associated with them. The category file
is structured so that each category in the raster file can have a one-line
description. The format of this file is described in
Raster_Category_File_Format.

<P>
The routines described below manage the category file. Some of them use the
<I>Categories</I> structure which is described in
GIS_Library_Data_Structures.

<P>

\section Reading_and_Writing_the_Raster_Category_File Reading and Writing the Raster Category File


<P>
The following routines read or write the category file itself:

<P>
int G_read_cats(char *name, char *mapset, struct Categories
  *cats) read raster category fileThe category file for raster file
  <B>name</B> in <B>mapset</B> is read into the <B>cats</B> structure. If
  there is an error reading the category file, a diagnostic message is printed
  and -1 is returned. Otherwise, 0 is returned.

<P>
int G_write_cats(char *name, struct Categories *cats) write raster
  category fileWrites the category file for the raster file <B>name</B> in
  the current mapset from the <B>cats</B> structure.

<P>
Returns 1 if successful. Otherwise, -1 is returned (no diagnostic is
  printed) .

<P>
char * G_get_cell_title(char *name, char *mapset) get raster map
  titleIf only the map layer title is needed, it is not necessary to read the
  entire category file into memory. This routine gets the title for raster file
  <B>name</B> in <B>mapset</B> directly from the category file, and returns
  a pointer to the title. A legal pointer is always returned. If the map layer
  does not have a title, then a pointer to the empty string "" is returned.

<P>
char * G_put_cell_title(char *name, char *title) change raster map
  titleIf it is only desired to change the title for a map layer, it is not
  necessary to read the entire category file into memory, change the title, and
  rewrite the category file. This routine changes the <B>title</B> for the
  raster file <B>name</B> in the current mapset directly in the category
  file. It returns a pointer to the title.

<P>

\section Querying_and_Changing_the_Categories_Structure Querying and Changing the Categories Structure


<P>
The following routines query or modify the information contained in the
category structure:

<P>
char * G_get_cat(CELL n, struct Categories *cats) get a category
  labelThis routine looks up category <B>n</B> in the <B>cats</B>
  structure and returns a pointer to a string which is the label for the
  category. A legal pointer is always returned. If the category does not exist
  in <B>cats,</B> then a pointer to the empty string "" is returned.

<P>
<B>Warning.</B> The pointer that is returned points to a hidden static
  buffer. Successive calls to G_get_cat() overwrite this buffer.

<P>
char * G_get_cats_title (Categories *cats) get title from category
  structure structMap layers store a one-line title in the category structure
  as well. This routine returns a pointer to the title contained in the
  <B>cats</B> structure.  A legal pointer is always returned. If the map
  layer does not have a title, then a pointer to the empty string "" is
  returned.

<P>
int G_init_cats(CELL n, char *title, struct Categories
  *cats) initialize category structureTo construct a new category file, the
  structure must first be initialized.  This routine initializes the
  <B>cats</B> structure, and copies the <B>title</B> into the structure.
  The number of categories is set initially to <B>n.</B>

<P>
For example:

<P>
\verbatim
struct Categories cats;

G_init_cats ((CELL) 0, '''', &cats) ;
\endverbatim

<P>
int G_set_cat(CELL n, char *label, struct Categories *cats) set a
  category labelThe <B>label</B> is copied into the <B>cats</B> structure
  for category <B>n.</B>

<P>
int G_set_cats_title(char *title, struct Categories *cats) set
  title in category structureThe <B>title</B> is copied into the
  <B>cats</B> structure.

<P>
int G_free_cats(struct Categories *cats) free category structure
  memoryFrees memory allocated by<I>G_read_cats, G_init_cats</I>
  and<I> G_set_cat.</I>

<P>

\section Raster_Color_Table Raster Color Table

<P>
GRASS map layers have colors associated with them. The color tables are
structured so that each category in the raster file has its own color. The
format of this file is described in Raster_Color_Table_Format.

<P>
The routines that manipulate the raster color file use the <I>Colors</I>
structure which is described in detail in
GIS_Library_Data_Structures.

<P>

\section Reading_and_Writing_the_Raster_Color_File Reading and Writing the Raster Color File

<P>
The following routines read, create, modify, and write color tables.

<P>
int G_read_colors(char *name, char *mapset, struct Colors
  *colors) read map layer color tableThe color table for the raster file
  <B>name</B> in the specified <B>mapset</B> is read into the
  <B>colors</B> structure.

<P>
If the data layer has no color table, a default color table is generated and
  0 is returned. If there is an error reading the color table, a diagnostic
  message is printed and -1 is returned. If the color table is read ok, 1 is
  returned.

<P>
int G_write_colors(char *name, char *mapset, struct Colors
  *colors) write map layer color tableThe color table is written for the
  raster file <B>name</B> in the specified <B>mapset</B> from the
  <B>colors</B> structure.

<P>
If there is an error, -1 is returned. No diagnostic is printed. Otherwise, 1
  is returned.

<P>
The <B>colors</B> structure must be created properly, i.e.,
  <I>G_init_colors</I> to initialize the structure and
  <I>G_add_color_rule</I> to set the category colors. [footnote]
<P>
<B>Note.</B> The calling sequence for this function deserves special
  attention. The <B>mapset</B> parameter seems to imply that it is possible
  to overwrite the color table for a raster file which is in another mapset.
  However, this is not what actually happens. It is very useful for users to
  create their own color tables for raster files in other mapsets, but without
  overwriting other users' color tables for the same raster file. If
  <B>mapset</B> is the current mapset, then the color file for <B>name</B>
  will be overwritten by the new color table. But if <B>mapset</B> is not the
  current mapset, then the color table is actually written in the current
  mapset under the <B>colr2</B> element as: colr2/mapset/name.

<P>

\section Lookup_Up_Raster_Colors Lookup Up Raster Colors


<P>
These routines translates raster values to their respective colors.

<P>
int G_lookup_colors(CELL *raster, unsigned char *red, unsigned char
  *green, unsigned char *blue, set, int n, struct Colors *colors) lookup an
  array of colorsExtracts colors for an array of <B>raster</B> values. The
  colors for the <B>n</B> values in the <B>raster</B> array are stored in
  the <B>red, green</B>, and <B>blue</B> arrays. The values in the
  <B>set</B> array will indicate if the corresponding <B>raster</B> value
  has a color or not (1 means it does, 0 means it does not) . The programmer
  must allocate the <B>red, green, blue</B>, and <B>set</B> arrays to be at
  least dimension <B>n.</B>

<P>
<B>Note.</B> The <B>red, green</B>, and <B>blue</B> intensities will be
  in the range 0 -­ 255.

<P>
int G_get_color(CELL cat, int *red, int *green, int *blue, struct
  Colors *colors) get a category colorThe <B>red, green</B>, and
  <B>blue</B> intensities for the color associated with category <B>cat</B>
  are extracted from the <B>colors</B> structure. The intensities will be in
  the range 0 ­- 255.

<P>

\section Creating_and_or_Modifying_the_Color_Table Creating and/or Modifying the Color Table


<P>
These routines allow the creation of customized color tables as well as the
modification of existing tables.

<P>
int G_init_colors(struct Colors *colors) initialize color
  structureThe <B>colors</B> structure is initialized for subsequent calls
  to <I>G_add_color_rule</I> and<I>G_set_color.</I>

<P>
int G_add_color_rule(CELL cat1, int r1, int g1, int b1, CELL cat2,
  int r2, int g2, int b2, struct Colors *colors) set colorsThis is the heart
  and soul of the new color logic. It adds a color rule to the <B>colors</B>
  structure. The colors defined by the red, green, and blue values
  <B>r1,g1,b1</B> and <B>r2,g2,b2</B> are assigned to <B>cat1</B> and
  <B>cat2</B> respectively. Colors for data values between <B>cat1</B> and
  <B>cat2</B> are not stored in the structure but are interpolated when
  queried by <I>G_lookup_colors</I> and<I> G_get_color.</I> The color
  components <B>r1,g1,b1</B> and <B>r2,g2,b2</B> must be in the range
  0 - 255.

<P>
For example, to create a linear grey scale for the range 200 - 1000:

<P>
\verbatim
struct Colors colr;

G_init_colors (&colr) ;

G_add_color_rule ((CELL) 200, 0,0,0,(CELL) 1000, 255,255,255) ;
\endverbatim


<P>
The programmer is encouraged to review Raster_Color_Table_Format how
this routine fits into the 5.x raster color logic.

<P>
<B>Note.</B> The <B>colors</B> structure must have been initialized by
<I>G_init_colors.</I> See \ref Predefined_Color_Tables for routines to
build some predefined color tables.

<P>
int G_set_color(CELL cat, int red, int green, int blue, struct
  Colors *colors) set a category colorThe <B>red, green</B>, and
  <B>blue</B> intensities for the color associated with category <B>cat</B>
  are set in the <B>colors</B> structure.  The intensities must be in the
  range 0 -­ 255. Values below zero are set as zero, values above 255 are set as
  255.

<P>
<B>Use of this routine is discouraged because it defeats the new color
    logic.</B> It is provided only for backward compatibility. Overuse can create
  large color tables. <I>G_add_color_rule</I> should be used whenever
  possible.

<P>
<B>Note.</B> The <B>colors</B> structure must have been initialized by
  <I>G_init_color.</I>

<P>
int G_get_color_range(CELL *min, CELL *max, struct Colors
*colors) get color rangeGets the minimum and maximum raster values that
have colors associated with them.

<P>
int G_free_colors(struct Colors *colors) free color structure
  memoryThe dynamically allocated memory associated with the <B>colors</B>
  structure is freed.

<P>
<B>Note.</B> This routine may be used after <I>G_read_colors</I> as
  well as after <I>G_init_colors.</I>

<P>

\section Predefined_Color_Tables Predefined Color Tables


<P>
The following routines generate entire color tables. The tables are loaded into
a <B>colors</B> structure based on a range of category values from
<B>min</B> to <B>max.</B> The range of values for a raster map can be
obtained, for example, using <I>G_read_range.</I> <B>Note.</B> The color
tables are generated without information about any particular raster file.

<P>
These color tables may be created for a raster file, but they may also be 
generated for loading graphics colors.

<P>
These routines return -1 if <B>min</B> is greater than <B>max</B>, 1
otherwise.

<P>
int G_make_aspect_colors(struct Colors *colors, CELL min, CELL
  max) make aspect colorsGenerates a color table for aspect data.

<P>
int G_make_ramp_colors(struct Colors *colors, CELL min, CELL
  max) make color rampGenerates a color table with 3 sections: red only,
  green only, and blue only, each increasing from none to full intensity. This
  table is good for continuous data, such as elevation.

<P>
int G_make_wave_colors(struct Colors *colors, CELL min, CELL
  max) make color waveGenerates a color table with 3 sections: red only,
  green only, and blue only, each increasing from none to full intensity and
  back down to none.  This table is good for continuous data like elevation.

<P>
int G_make_grey_scale_colors(struct Colors *colors, CELL min, CELL
  max) make linear grey scaleGenerates a grey scale color table. Each color
  is a level of grey, increasing from black to white.

<P>
int G_make_rainbow_colors(struct Colors *colors, CELL min, CELL
  max) make rainbow colorsGenerates a "shifted" rainbow color table - yellow
  to green to cyan to blue to magenta to red. The color table is based on
  rainbow colors. (Normal rainbow colors are red, orange, yellow, green, blue,
  indigo, and violet.)  This table is good for continuous data, such as
  elevation.

<P>
int G_make_random_colors(struct Colors *colors, CELL min, CELL
  max) make random colorsGenerates random colors. Good as a first pass at a
  color table for nominal data.

<P>
int G_make_ryg_colors(struct Colors *colors, CELL min, CELL
  max) make red,yellow,green colorsGenerates a color table that goes from
  red to yellow to green.

<P>
int G_make_gyr_colors(struct Colors *colors, CELL min, CELL
  max) make green,yellow,red colorsGenerates a color table that goes from
  green to yellow to red.

<P>
int G_make_histogram_eq_colors(struct Colors *colors, struct
  Cell_stats *s) make histogram-stretched grey colorsGenerates a histogram
  contrast-stretched grey scale color table that goes from the ,histogram
  information in the Cell_stats structure <B>s.</B>  (See
  Raster_Histograms) .

<P>

\section Raster_History_File Raster History File


<P>
The history file contains documentary information about the raster file: who
created it, when it was created, what was the original data source, what
information is contained in the raster file, etc. This file is discussed in
Raster_History_File_Format

<P>
The following routines manage this file. They use the <I>History</I>
structure which is described in GIS_Library_Data_Structures.

<P>
<B>Note.</B> This structure has existed relatively unmodified since the
inception of GRASS. It is in need of overhaul. Programmers should be aware that
future versions of GRASS may no longer support either the routines or the data
structure which support the history file.

<P>
int G_read_history(char *name, char *mapset, struct History
  *history) read raster history fileThis routine reads the history file for
  the raster file <B>name</B> in <B>mapset</B> into the <B>history</B>
  structure.

<P>
A diagnostic message is printed and -1 is returned if there is an error
  reading the history file. Otherwise, 0 is returned.

<P>
int G_write_history(char *name, struct History *history) write
  raster history fileThis routine writes the history file for the raster file
  <B>name</B> in the current mapset from the <B>history</B> structure.

<P>
A diagnostic message is printed and -1 is returned if there is an error
  writing the history file. Otherwise, 0 is returned.

<P>
<B>Note.</B> The <B>history</B> structure should first be initialized
  using <I>G_short_history.</I>

<P>
int G_short_history(char *name, char *type, struct History
  *history) initialize history structureThis routine initializes the
  <B>history</B> structure, recording the date, user, module name and the
  raster file <B>name</B> structure. The <B>type</B> is an anachronism from
  earlier versions of GRASS and should be specified as "raster".

<P>
<B>Note.</B> This routine only initializes the data structure. It does not
  write the history file.

<P>

\section Raster_Range_File Raster Range File

<P>
The following routines manage the raster range file. This file contains the
minimum and maximum values found in the raster file. The format of this file is
described in Raster_Range_File_Format.

<P>
The routines below use the <I>Range</I> data structure which is described in
GIS_Library_Data_Structures.

<P>
int G_read_range(char *name, char *mapset, struct Range
  *range) read raster rangeThis routine reads the range information for the
  raster file <B>name</B> in <B>mapset</B> into the <B>range</B>
  structure.

<P>
A diagnostic message is printed and -1 is returned if there is an error
  reading the range file. Otherwise, 0 is returned.

<P>
int G_write_range(char *name, struct Range *range) write raster
  range fileThis routine writes the range information for the raster file
  <B>name</B> in the current mapset from the <B>range</B> structure.

<P>
A diagnostic message is printed and -1 is returned if there is an error
  writing the range file. Otherwise, 0 is returned.

<P>
The range structure must be initialized and updated using the following
routines:

<P>
int G_init_range(struct Range *range) initialize range
  structureInitializes the <B>range</B> structure for updates by
  <I>G_update_range</I> and <I>G_row_update_range.</I>

<P>
int G_update_range(CELL cat, struct Range *range) update range
  structureCompares the <B>cat</B> value with the minimum and maximum
  values in the <B>range</B> structure, modifying the range if <B>cat</B>
  extends the range.

<P>
int G_row_update_range(CELL *cell, int n, struct Range
  *range) update range structureThis routine updates the <B>range</B> data
  just like <I>G_update_range</I>, but for <B>n</B> values from the
  <B>cell</B> array.

<P>
The range structure is queried using the following routine:

<P>
int G_get_range_min_max(struct Range *range, CELL *min, CELL
  *max) get range min and maxThe <B>min</B>inum and <B>max</B>imum CELL
  values are extracted from the <B>range</B> structure.

<P>

\section Raster_Histograms Raster Histograms


<P>
The following routines provide a relatively efficient mechanism for computing
and querying a histogram of raster data. They use the <I>Cell_stats</I>
structure to hold the histogram information. The histogram is a count
associated with each unique raster value representing the number of times each
value was inserted into the structure.

<P>
These next two routines are used to manage the Cell_stats structure:

<P>
int G_init_cell_stats(struct Cell_stats *s) initialize cell
  statsThis routine, which must be called first, initializes the Cell_stats
  structure <B>s.</B>

<P>
int G_free_cell_stats(struct Cell_stats *s) free cell statsThe
  memory associated with structure <B>s</B> is freed. This routine may be
  called any time after calling<I>G_init_cell_stats.</I>

<P>
This next routine stores values in the histogram:

<P>
int G_update_cell_stats(CELL *data, int n, struct Cell_stats
  *s) add data to cell statsThe <B>n</B> CELL values in the <B>data</B>
  array are inserted (and counted) in the Cell_stats structure <B>s.</B>

<P>
Once all values are stored, the structure may be queried either randomly (ie.
search for a specific raster value) or sequentially (retrieve all raster
values, in ascending order, and their related count) :

<P>
int G_find_cell_stat(CELL cat, long *count, struct Cell_stats
  *s) random query of cell statsThis routine allows a random query of the
  Cell_stats structure <B>s.</B>  The <B>count</B> associated with the
  raster value <B>cat</B> is set. The routine returns 1 if <B>cat</B> was
  found in the structure, 0 otherwise.

<P>
Sequential retrieval is accomplished using these next 2 routines:

<P>
int G_rewind_cell_stats(struct Cell_stats *s) reset/rewind cell
  statsThe structure <B>s</B> is rewound (i.e., positioned at the first
  raster category) so that sorted sequential retrieval can begin.

<P>
int G_next_cell_stat(CELL *cat, long *count, struct Cell_stats
  *s) retrieve sorted cell stats Retrieves the next <B>cat,count</B>
  combination from the structure <B>s.</B> Returns 0 if there are no more
  items, non-zero if there are more.

<P>
For example:

<P>
\verbatim
struct Cell_stats s;
CELL cat;
long count;

.
. /* updating s occurs here */
.

G_rewind_cell_stats(&s);

while (G_next_cell_stat(&cat,&count,&s)
  fprintf(stdout, "%ld %ld\n", (long) cat, count);
\endverbatim

<P>

\section  GRASS_5_raster_API GRASS 5 raster API [needs to be merged
      into above sections]


\subsection The_CELL_Data_Type The CELL Data Type

GRASS integer raster map data is defined to be of type CELL. This data
type is defined in the "gis.h" header file. Programmers must declare
all variables and buffers which will hold raster data or category
codes as type CELL.  Under GRASS the CELL data type is declared to be
int, but the programmer should not assume this. What should be assumed
is that CELL is a signed integer type. It may be changed sometime to
short or long. This implies that use of CELL data with routines which
do not know about this data type (e.g., fprintf(stdout, ...), sscanf(),
etc.) must use an intermediate variable of type long.  To print a CELL
value, it must be cast to long. For example:

\verbatim
CELL c; /* raster value to be printed */

/* some code to get a value for c */
fprintf(stdout, "%ld\n", (long) c); /* cast c to long to print */
\endverbatim

To read a CELL value, for example from user typed input, it is
necessary to read into a long variable, and then assign it to the CELL
variable. For example (this example does not check for valid inputs,
EOF, etc., which good code must do):

\verbatim
char userbuf[128];
CELL c; long x;

fprintf (stdout, "Which category? "); /* prompt user */
gets(userbuf); /* get user response * /
sscanf (userbuf,"%ld", &x); /* scan category into long variable */
c = (CELL) x; /* assign long value to CELL value */
\endverbatim

Of course, with GRASS library routines that are designed to handle the
CELL type, this problem does not arise. It is only when CELL data must
be used in routines which do not know about the CELL type, that the
values must be cast to or from long.


\subsection 5.0 Changes to  <TT>"gis.h"</TT>


<P>
The <TT>"gis.h"</TT>  contains 5 new items:

<P>
<PRE>         
        typedef float FCELL
        typedef double DCELL
        typedef int RASTER_MAP_TYPE;
        #define CELL_TYPE 0
        #define FCELL_TYPE 1
        #define DCELL_TYPE 2
</PRE>

<P>
Also <TT>"gis.h"</TT> contains the definitions for new structures:

<P>
<PRE>       
      struct FPReclass;
      struct FPRange;
      struct Quant;
</PRE>

<P>
Some of the old structures such as

<P>
<PRE>
      struct Categories
      struct Cell_stats;
      struct Range;
      struct _Color_Rule_;
      struct _Color_Info_;
      struct Colors;
</PRE>

<P>
were modified, so it is very important to use functional interface to access
and set elements of these structures instead of accessing elements of the
structures directly. Because some former elements such as for example
<TT>(struct Range range.pmin) </TT> do not exist anymore. It was made sure non
of the former elements have different meaning, so that the programs which do
access the old elements directly either do not compile or work exactly the same
way as prior to change.

<P>

\subsection NULL_value_functions NULL-value functions


<P>
int G_set_null_value(void *rast, int count, RASTER_MAP_TYPE
  data_type) Set NULL valueIf the <EM>data_type</EM> is CELL_TYPE, calls
  G_set_c_null_value((CELL *) rast, count) ;

<P>
If the <EM>data_type</EM> is FCELL_TYPE, calls G_set_f_null_value((FCELL
  *) rast, count) ;

<P>
If the <EM>data_type</EM> is DCELL_TYPE, calls G_set_d_null_value((DCELL
  *) rast, count) ;

<P>
int G_set_c_null_value(CELL *cell, int count) Set CELL NULL
  valueSet the <EM>count</EM> elements in the <EM>cell</EM> array to the NULL value
  (the largest positive integer) .

<P>
int G_set_f_null_value(FCELL *fcell, int count) Set FCELL NULL
  valueSet the <EM>count</EM> elements in the <EM>fcell</EM> array to the NULL
  value (a bit pattern for a <TT>float</TT> NaN - 32 bits of 1's) .

<P>
int G_set_d_null_value(DCELL *dcell, int count) Set CELL NULL
  valueSet the <EM>count</EM> elements in the <EM>dcell</EM> array to the NULL
  value - which (a bit pattern for a <TT>double</TT> NaN - 64 bits of 1's) .

<P>
int G_insert_null_values(void *rast, char *flags, int count,
  RASTER_MAP_TYPE data_type) Insert NULL valueIf the <EM>data_type</EM> is
  CELL_TYPE, calls G_insert_c_null_values ((CELL *) rast, flags, count) ;

<P>
If the <EM>data_type</EM> is FCELL_TYPE, calls G_insert_f_null_values
  ((FCELL *) rast, flags, count) ;

<P>
If the <EM>data_type</EM> is DCELL_TYPE, calls G_insert_d_null_values
  ((DCELL *) rast, flags, count) ;

<P>
int G_insert_c_null_values(CELL *cell, char *flags, int
  count) Insert CELL NULL value For each of the <EM>count</EM> <EM>flags</EM>
  which is true(!=0) , set the corresponding <EM>cell</EM> to the NULL value.

<P>
int G_insert_f_null_values(FCELL *fcell, char *flags, int
  count) Insert FCELL NULL value For each of the <EM>count</EM> <EM>flags</EM>
  which is true(!=0) , set the corresponding <EM>fcell</EM> to the NULL value.

<P>
int G_insert_d_null_values(DCELL *dcell, char *flags, int
  count) Insert DCELL NULL value For each for the <EM>count</EM> <EM>flag</EM>
  which is true(!=0) , set the corresponding <EM>dcell</EM> to the NULL value.

<P>
int G_is_null_value(void *rast, RASTER_MAP_TYPE data_type) If
  the <EM>data_type</EM> is CELL_TYPE, calls G_is_c_null_value ((CELL *) 
  rast) ;

<P>
If the <EM>data_type</EM> is FCELL_TYPE, calls G_is_f_null_value ((FCELL
  *) rast) ;

<P>
If the <EM>data_type</EM> is DCELL_TYPE, calls G_is_d_null_value ((DCELL
  *) rast) ;

<P>
int G_is_c_null_value(CELL *cell) Returns 1 if <EM>cell</EM> is
  NULL, 0 otherwise. This will test if the value <EM>cell</EM> is the largest <TT>int</TT>.

<P>
int G_is_f_null_value(FCELL *fcell) Returns 1 if <EM>fcell</EM>
  is NULL, 0 otherwise. This will test if the value <EM>fcell</EM> is a NaN. It
  isn't good enough to test for a particular NaN bit pattern since the machine
  code may change this bit pattern to a different NaN. The test will be

<P>
\verbatim
if(fcell == 0.0) return 0;
if(fcell >  0.0) return 0;
if(fcell <  0.0) return 0;
return 1;
\endverbatim
<BR>

<P>
or (as suggested by Mark Line) 

<P>
\verbatim
return(FCELL != fcell) ;
\endverbatim

<P>
int G_is_d_null_value(DCELL *dcell) Returns 1 if <EM>dcell</EM> is
  NULL, 0 otherwise. This will test if the value <EM>dcell</EM> is a NaN. Same
  test as in <TT>G_is_f_null_value()</TT>.

<P>
char * G_allocate_null_buf() Allocate an array of char based on
  the number of columns in the current region.

<P>
int G_get_null_value_row (int fd, char *flags, int row) Reads a
  row from NULL value bitmap file for the raster map open for read on <EM>fd</EM>.
  If there is no bitmap file, then this routine simulates the read as follows:
  non-zero values in the raster map correspond to non-NULL; zero values
  correspond to NULL. When MASK exists, masked cells are set to null. <EM>
  flags</EM> is a resulting array of 0's and 1's where 1 corresponds to
  <TT>"no data"</TT> cell.

<P>

\subsection Floating_point_and_type_independent_functions Floating-point and type-independent functions


<P>
int G_maskfd(void) test for current maskreturns file descriptor
  number if MASK is in use and -1 if no MASK is in use.

<P>
int G_raster_map_is_fp(char *name, char *mapset) Returns true(1) 
  if raster map <EM>name</EM> in <EM>mapset</EM> is a floating-point dataset;
  false(0) otherwise.

<P>
int G_raster_map_type(char *name, char *mapset) Returns the
  storage type for raster map <EM>name</EM> in <EM>mapset</EM>: <TT>CELL_TYPE</TT>
  (int) ; <TT>FCELL_TYPE</TT> (float) ; or <TT>DCELL_TYPE</TT> (double) .

<P>
int G_open_raster_new[_uncompressed](char *name,
  RASTER_MAP_TYPE map_type) If map_type == CELL_TYPE, calls
  G_open_map_new[_uncompressed](name) ;

<P>
If map_type == FCELL_TYPE, calls G_set_fp_type(FCELL_TYPE) ;
  G_open_fp_map_new[_uncompressed](name) ;

<P>
If map_type == DCELL_TYPE, calls G_set_fp_type(DCELL_TYPE) ;
  G_open_fp_map_new[_uncompressed](name) ;

<P>
The use of this routine by applications is discouraged since its use would override user
  preferences (what precision to use) .

<P>
int G_set_fp_type (RASTER_MAP_TYPE type) This controls the
  storage type for floating-point maps. It affects subsequent calls to 
  <TT>G_open_fp_map_new()</TT>. The <EM>type</EM> must be one of <TT>FCELL_TYPE</TT>
  (float) or <TT>DCELL_TYPE</TT> (double) . The use of this routine by
  applications is discouraged since its use would override user preferences.

<P>
int G_open_fp_map_new(char *name) Opens a new floating-point
  raster map (in <TT>.tmp</TT>) and returns a file descriptor. The storage type
  (<TT>float</TT> or <TT>double</TT>) is determined by the last call to 
  <TT>G_set_fp_type()</TT> or the default (<TT>float</TT> - unless the Unix env
  variable GRASS_FP_DOUBLE is set) .

<P>
void * G_allocate_raster_buf(RASTER_MAP_TYPE
  data_type) Allocate an array of CELL, FCELL, or DCELL (depending on <EM>
  data_type</EM>) based on the number of columns in the current region.

<P>
CELL * G_allocate_c_raster_buf() Allocate an array of CELL
  based on the number of columns in the current region.

<P>
FCELL * G_allocate_f_raster_buf() Allocate an array of FCELL
  based on the number of columns in the current region.

<P>
DCELL * G_allocate_d_raster_buf() Allocate an array of DCELL
  based on the number of columns in the current region.

<P>
void * G_incr_void_ptr(void *ptr, int size) Advances void
  pointer by n bytes. returns new pointer value. Usefull in raster row
  processing loops, substitutes 

<P>
\verbatim
CELL *cell;
cell += n;
\endverbatim

<P>
Now 

\verbatim
rast = G_incr_void_ptr(rast, G_raster_size(data_type) ) 
\endverbatim

<P>
(where rast is void* and data_type is RASTER_MAP_TYPE can be used instead
 of rast++.)  very usefull to generalize the row processing - loop (i.e. void *
 buf_ptr += G_raster_size(data_type) 

<P>
int G_raster_size (RASTER_MAP_TYPE data_type) If <EM>data_type</EM> is CELL_TYPE, returns sizeof(CELL) 

<P>
If <EM>data_type</EM> is FCELL_TYPE, returns sizeof(FCELL) 

<P>
If <EM>data_type</EM> is DCELL_TYPE,q returns sizeof(DCELL) 

<P>
int G_raster_cmp(void *p, *q, RASTER_MAP_TYPE
  data_type) Compares raster vlues p and q. Returns 1 if p &gt; q or only q is
  null value -1 if p &lt; q or only p is null value 0 if p == q or
  p==q==null value

<P>
int G_raster_cpy(void *p, void *q, int n, RASTER_MAP_TYPE
  data_type) Copies raster values q into p. If q is null value, sets q to
  null value.

<P>
int G_set_raster_value_c(void *p, CELL val, RASTER_MAP_TYPE
  data_type) If G_is_c_null_value(val) is true, sets p to null value.
  Converts CELL val to data_type (type of p) and stores result in p. Used for
  assigning CELL values to raster cells of any type.

<P>
int G_set_raster_value_f(void *p, FCELL val, RASTER_MAP_TYPE
  data_type) If G_is_f_null_value(val) is true, sets p to null value.
  Converts FCELL val to data_type (type of p) and stores result in p. Used for
  assigning FCELL values to raster cells of any type.

<P>
int G_set_raster_value_d(void *p, DCELL val, RASTER_MAP_TYPE
  data_type) If G_is_d_null_value(val) is true, sets p to null value.
  Converts DCELL val to data_type (type of p) and stores result in p. Used for
  assigning DCELL values to raster cells of any type.

<P>
CELL G_get_raster_value_c(void *p, RASTER_MAP_TYPE
  data_type) Retrieves the value of type data_type from pointer p,
  converts it to CELL type and returns the result. If null value is stored in
  p, returns CELL null value. Used for retreiving CELL values from raster cells
  of any type.  NOTE: when data_type != CELL_TYPE, no quantization is used,
  only type conversion.

<P>
FCELL G_get_raster_value_f(void *p, RASTER_MAP_TYPE
  data_type) Retrieves the value of type data_type from pointer p,
  converts it to FCELL type and returns the result. If null value is stored in
  p, returns FCELL null value. Used for retreiving FCELL values from raster
  cells of any type.

<P>
DCELL G_get_raster_value_d(void *p, RASTER_MAP_TYPE
  data_type) Retrieves the value of type data_type from pointer p,
  converts it to DCELL type and returns the result. If null value is stored in
  p, returns DCELL null value. Used for retreiving DCELL values from raster
  cells of any type.

<P>
int G_get_raster_row (int fd, void *rast, int row, RASTER_MAP_TYPE
  data_type) If <EM>data_type</EM> is CELL_TYPE, calls
  G_get_c_raster_row(fd,(CELL *) rast, row) ;

<P>
If <EM>data_type</EM> is FCELL_TYPE, calls G_get_f_raster_row(fd,(FCELL
  *) rast, row) ;

<P>
If <EM>data_type</EM> is DCELL_TYPE, calls G_get_d_raster_row(fd,(DCELL
  *) rast, row) ;

<P>
int G_get_raster_row_nomask (int fd, FCELL *fcell, int row,
  RASTER_MAP_TYPE map_type) Same as <TT>G_get_f_raster_row()</TT>
  except no masking occurs.

<P>
int G_get_f_raster_row (int fd, FCELL fcell, int row) Read a row
  from the raster map open on <EM>fd</EM> into the <TT>float</TT> array <EM>fcell</EM>
  performing type conversions as necessary based on the actual storage type of
  the map. Masking, resampling into the current region.  NULL-values are always
  embedded in <TT>fcell</TT> (<EM>never converted to a value</EM>) .

<P>
int G_get_f_raster_row_nomask (int fd, FCELL *fcell, int row) 
  Same as <TT>G_get_f_raster_row()</TT> except no masking occurs.

<P>
int G_get_d_raster_row (int fd, DCELL *dcell, int row) Same as
  <TT>G_get_f_raster_row()</TT> except that the array <EM>dcell</EM> is <TT>double</TT>.

<P>
int G_get_d_raster_row_nomask (int fd, DECLL *dcell, int row) 
  Same as <TT>G_get_d_raster_row()</TT> except no masking occurs.

<P>
int G_get_c_raster_row (int fd, CELL buf, int row) Reads a row
  of raster data and leaves the NULL values intact. (As opposed to the
  deprecated function <TT>G_get_map_row()</TT> which converts NULL values to
  zero.) 

<P>
<B>NOTE.</B> When the raster map is old and null file doesn't exist, it is
  assumed that all 0-cells are no-data. When map is floating point, uses quant
  rules set explicitly by G_set_quant_rules or stored in map's quant file to
  convert floats to integers.

<P>
int G_get_c_raster_row_nomask (int fd, CELL buf, int row) Same
  as <TT>G_get_c_raster_row()</TT> except no masking occurs.

<P>
int G_put_raster_row (int fd, void *rast, RASTER_MAP_TYPE
  data_type) If <EM>data_type</EM> is CELL_TYPE, calls
  G_put_c_raster_row(fd,(CELL *) rast) ;

<P>
If <EM>data_type</EM> is FCELL_TYPE, calls G_put_f_raster_row(fd,(FCELL
  *) rast) ;

<P>
If <EM>data_type</EM> is DCELL_TYPE, calls G_put_d_raster_row(fd,(DCELL
  *) rast) ;

<P>
int G_put_f_raster_row (int fd, FCELL *fcell) Write the next row
  of the raster map open on <EM>fd</EM> from the <TT>float</TT> array <EM>fcell</EM>,
  performing type conversion to the actual storage type of the resultant map.
  Keep track of the range of floating-point values.  Also writes the NULL-value
  bitmap from the NULL-values embedded in the <EM>fcell</EM> array.

<P>
int G_put_d_raster_row (int fd, DCELL *dcell) Same as <TT>G_put_f_raster_row()</TT> 
except that the array <EM>dcell</EM> is <TT>double</TT>.

<P>
int G_put_c_raster_row (int fd, CELL buf) Writes a row of raster
  data and a row of the null-value bitmap, only treating NULL as NULL. (As
  opposed to the deprecated function <TT>G_put_map_row()</TT> which treats zero
  values also as NULL.) 

<P>
int G_zero_raster_row(void *rast, RASTER_MAP_TYPE
  data_type) Depending on <EM>data_type</EM> zeroes out G_window_cols() 
  CELLs, FCELLs, or DCELLs stored in cell buffer.

<P>
double G_get_raster_sample(int, struct Cell_head *, struct Categories *,
             double, double, int, INTERP_TYPE)
extracts a cell value from raster map at given position with
INTERP_TYPE 0:UNKNOWN; 1: nearest neighbor interpolation;
2: bilinear interpolation; 3: cubic interpolation.

\section Upgrades_to_Raster_Functions Upgrades to Raster Functions  (comparing to GRASS 4.x)


<P>
These routines will be modified (internally) to work with floating-point and
NULL-values.

<P>
Changes to <TT>GISLIB</TT>:

<P>
int G_close_cell() If the map is a new floating point, move the
  <TT>.tmp</TT> file into the <TT>fcell</TT> element, create an empty file in the
  <TT>cell</TT> directory; write the floating-point range file; write a default
  quantization file quantization file is set here to round fp numbers (this is
  a default for now) . create an empty category file, with max cat = max value
  (for backwards compatibility) . Move the <TT>.tmp</TT> NULL-value bitmap file to
  the <TT>cell_misc</TT> directory.

<P>
int G_open_cell_old() Arrange for the NULL-value bitmap to be
  read as well as the raster map.  If no NULL-value bitmap exists, arrange for
  the production of NULL-values based on zeros in the raster map.

<P>
If the map is floating-point, arrange for quantization to integer for <TT>G_get_c_raster_row()</TT>,
 et. al., by reading the quantization rules for
  the map using <TT>G_read_quant()</TT>.

<P>
If the programmer wants to read the floating point map using uing quant rules
  other than the ones stored in map's quant file, he/she should call
  G_set_quant_rules() after the call to G_open_cell_old() .

<P>
int G_get_map_row() If the map is floating-point, quantize the
  floating-point values to integer using the quantization rules established for
  the map when the map was opened for reading (this quantization is read from
  cell_misc/name/f_quant file, but can be reset after opening raster map by
  G_set_quant_rules() ) .

<P>
NULL values are converted to zeros.

<P>
<B>This routine is deprecated!!</B>

<P>
int G_put_map_row() Zero values are converted to NULLs. Write a
  row of the NULL value bit map.

<P>
<B>This routine is deprecated!!</B>

<P>
Changes to <TT>D_LIB</TT>:

<P>
int Dcell() If the map is a floating-point map, read the map using
  <TT>G_get_d_map_row()</TT> and plot using <TT>D_draw_d_cell()</TT>. If the
  map is an integer map, read the map using <TT>G_get_c_raster_row()</TT> and
  plot using <TT>D_draw_cell()</TT>.

<P>

\section Null_no_data NULL (no data) handling

-2^31 (= 0x80000000 = -2147483648) is the null value
for the CELL type, so you'll never see that value in a map.

The FP nulls are the all-ones bit patterns. These corresponds to NaN
according to the IEEE-754 formats, although it isn't the "default" NaN
pattern generated by most architectures (which is usually 7fc00000 or
ffc00000 for float and 7ff8000000000000 or fff8000000000000 for
double, i.e. an all-ones exponent, the top-bit of the mantissa set,
and either sign).

So far as arithmetic is concerned, any value with an all-ones exponent
and a non-zero mantissa is treated as NaN. But the GRASS
G_is_[fd]_null_value() functions only consider the all-ones bit
pattern to be null. I intend to change this in 7.x so that all FP NaN
values are treated as null. This will mean that code which can
generate NaNs doesn't have to explicitly convert them to the GRASS
null value.

\section Color_Functions Color Functions (new and upgraded)

\subsection Upgraded_Colors_structures Upgraded Colors structures


<P>
\verbatim
struct _Color_Rule_

{

struct

{
    int version;        /* set by read\_colors: -1=old,1=new */
    DCELL shift;
    int invert;
    int is_float;             /* defined on floating point raster data? */
    int null_set; /* the colors for null are set? */
    unsigned char null_red, null_grn, null_blu;
    int undef_set; /* the colors for cells not in range are set? */
    unsigned char undef_red, undef_grn, undef_blu;
    struct _Color_Info_ fixed, modular;
    DCELL cmin, cmax;
};
\endverbatim

<P>

\section New_functions_to_support_colors_for_floating_point New functions to support colors for floating-point


<P>
Changes to <TT>GISLIB</TT>:

<P>
int G_lookup_raster_colors(void *rast, char *r, char *g, char *b,
  char *set, int n, struct Colors *colors, RASTER_MAP_TYPE cell_type) If
  the <EM>cell_type</EM> is CELL_TYPE, calls G_lookup_colors((CELL *) cell, r,
  g, b, set, n, colors) ;

<P>
If the <EM>cell_type</EM> is FCELL_TYPE, calls
  G_lookup_f_raster_colors(FCELL *) cell, r, g, b, set, n, colors) ;

<P>
If the <EM>cell_type</EM> is DCELL_TYPE, calls
  G_lookup_d_raster_colors(DCELL *) cell, r, g, b, set, n, colors) ;

<P>
int G_lookup_c_raster_colors(CELL *cell, char *r, char *g, char
  *b, char *set, int n, struct Colors *colors) The same as
  G_lookup_colors(cell, r, g, b, set, n, colors) .

<P>
int G_lookup_f_raster_colors(FCELL *fcell, char *r, char *g, char
  *b, char *set, int n, struct Colors *colors) Converts the <EM>n</EM>
  floating-point values in the <EM>fcell</EM> array to their <EM>r,g,b</EM> color
  components. Embedded NULL-values are handled properly as well.

<P>
int G_lookup_d_raster_colors(DCELL *dcell, char *r, char *g, char
  *b, char *set, int n, struct Colors *colors) Converts the <EM>n</EM>
  floating-point values in the <EM>dcell</EM> array to their <EM>r,g,b</EM> color
  components. Embedded NULL-values are handled properly as well.

<P>
int G_add_raster_color_rule(void *v1, int r1, int g1, int b1, void *v2, int r2, int g2, int b2,
  struct Colors *colors, RASTER_MAP_TYPE map_type) If <EM>map_type</EM> is CELL_TYPE, calls G_add_c_raster_color_rule ((CELL
  *) v1, r1, g1, b1,(CELL *) v2, r2, g2, b2, colors) ;

<P>
If <EM>map_type</EM> is FCELL_TYPE, calls G_add_f_raster_color_rule
  ((FCELL *) v1, r1, g1, b1,(FCELL *) v2, r2, g2, b2, colors) ;

<P>
If <EM>map_type</EM> is DCELL_TYPE, calls G_add_d_raster_color_rule
  ((DCELL *) v1, r1, g1, b1,(DCELL *) v2, r2, g2, b2, colors) ;

<P>
int G_add_c_raster_color_rule(CELL *v1, int r1, int g1, int b1,
  CELL *v2, int r2, int g2, int b2, struct Colors *colors) Calls
  G_add_color_rule(*v1, r1, g1, b1, *v2, r2, g2, b2, colors) .

<P>
int G_add_f_raster_color_rule(FCELL *v1, int r1, int g1, int b1,
  FCELL *v2, int r2, int g2, int b2, struct Colors *colors) Adds the
  floating-point rule that the range [<EM>v1,v2</EM>] gets a
  linear ramp of colors from [<EM>r1,g1,b1</EM>] to
  [<EM>r2,g2,b2</EM>].

<P>
If either <EM>v1</EM> or <EM>v2</EM> is the NULL-value, this call is converted into
  <TT>G_set_null_value_color (r1, g1, b1, colors) </TT>

<P>
int G_add_d_raster_color_rule(DCELL *v1, int r1, int g1, int b1,
  DCELL *v2, int r2, int g2, int b2, struct Colors *colors) Adds the
  floating-point rule that the range [<EM>v1,v2</EM>] gets a
  linear ramp of colors from [<EM>r1,g1,b1</EM>] to
  [<EM>r2,g2,b2</EM>].

<P>
If either <EM>v1</EM> or <EM>v2</EM> is the NULL-value, this call is converted into
  <TT>G_set_null_value_color (r1, g1, b1, colors) </TT>

<P>
int G_get_raster_color(void *v, int *r, int *g, int *b, struct
  Colors *colors, RASTER_MAP_TYPE data_type) Looks up the rgb colors for
  <EM>v</EM> in the color table <EM>colors</EM>

<P>
int G_get_c_raster_color(CELL *v, int *r, int *g, int *b, struct
  Colors *colors) Calls G_get_color(*v, r, g, b, colors) .

<P>
int G_get_f_raster_color(FCELL *v, int *r, int *g, int *b, struct
  Colors *colors) Looks up the rgb colors for <EM>v</EM> in the color table
  <EM>colors</EM>

<P>
int G_get_d_raster_color(DCELL *v, int *r, int *g, int *b, struct
  Colors *colors) Looks up the rgb colors for <EM>v</EM> in the color table
  <EM>colors</EM>

<P>
int G_set_raster_color(void *v, int r, int g, int b, struct Colors
  *colors, RASTER_MAP_TYPE data_type) calls <TT>G_add_raster_color_rule (v, r, g, b, v, r, g, r, colors, data_type) ;</TT>

<P>
int G_set_c_raster_color(CELL *v, int r, int g, int b, struct
  Colors *colors) Calls G_set_color(*v, r, g, b, colors) .

<P>
int G_set_f_raster_color(FCELL *v, int r, int g, int b, struct
  Colors *colors) Inserts a rule that assigns the color <EM>r,g,b</EM> to <EM>v</EM>. It is implemented as:

<P>
<TT>G_add_f_raster_color_rule (v, r, g, b, v, r, g, r, colors) ;</TT>

<P>
int G_set_d_raster_color(DCELL *v, int r, int g, int b, struct
  Colors *colors) Inserts a rule that assigns the color <EM>r,g,b</EM> to <EM>v</EM>. It is implemented as:

<P>
<TT>G_add_d_raster_color_rule (v, r, g, b, v, r, g, r, colors) ;</TT>

<P>
int G_mark_colors_as_fp(struct Colors *colors) Sets a flag in
  the <EM>colors</EM> structure that indicates that these colors should only be
  looked up using floating-point raster data (not integer data) .

<P>
In particular if this flag is set, the routine <TT>G_get_colors_min_max()</TT> should return 
min=-255&#94;3 and max=255&#94;3.
<P>

<P><P>
<BR>
<B>These routines are in the <TT>DISPLAYLIB</TT>:</B>

<P>
int D_raster_of_type(void *rast, int ncols, int nrows, struct
  Colors *colors, RASTER_MAP_TYPE data_type) If <EM>map_type</EM> is
  CELL_TYPE, calls D_raster((CELL *) rast, ncols, nrows, colors) ;

<P>
If <EM>map_type</EM> is FCELL_TYPE, calls D_f_raster((FCELL *) rast, ncols,
  nrows, colors) ;

<P>
If <EM>map_type</EM> is DCELL_TYPE, calls D_d_raster((DCELL *) rast, ncols,
  nrows, colors) ;

<P>
int D_f_raster(FCELL *fcell, int ncols, int nrows, struct Colors
  *colors) Same functionality as <TT>D_raster()</TT> except that the <EM>fcell</EM> 
  array is type <TT>FCELL</TT>. This implies that the floating-point
  interfaces to the <EM>colors</EM> are used by this routine.

<P>
int D_d_raster(DCELL *dcell, int ncols, int nrows, struct Colors
  *colors) Same functionality as <TT>D_raster()</TT> except that the <EM>dcell</EM> 
  array is type <TT>DCELL</TT>. This implies that the floating-point
  interfaces to the <EM>colors</EM> are used by this routine.

<P>
int D_color_of_type(void *value, struct Colors *colors,
  RASTER_MAP_TYPE data_type) If the <EM>data_type</EM> is CELL_TYPE,
  calls D_color((CELL *value, colors) ;

<P>
If the <EM>data_type</EM> is FCELL_TYPE, calls D_f_color((FCELL *value,
  colors) ;

<P>
If the <EM>data_type</EM> is DCELL_TYPE, calls D_d_color((DCELL *value,
  colors) ;

<P>
int D_f_color(FCELL *value, struct Colors *colors) Same
  functionality as <TT>D_color()</TT> except that the <EM>value</EM> is type <TT>FCELL</TT>. 
  This implies that the floating-point interfaces to the <EM>colors</EM> are used by this routine.

<P>
int D_d_color(DCELL *value, struct Colors *colors) Same
  functionality as <TT>D_color()</TT> except that the <EM>value</EM> is type <TT>DCELL</TT>.  
  This implies that the floating-point interfaces to the <EM>colors</EM> are used by this routine.

<P>
int D_lookup_raster_colors(void *rast, int *colornum, int n, struct
  Colors *colors, RASTER_MAP_TYPE data_type) If the <EM>data_type</EM> is
  CELL_TYPE, calls D_lookup_c_raster_colors((CELL *) rast, colornum, n,
  colors) ;

<P>
If the <EM>data_type</EM> is FCELL_TYPE, calls
  D_lookup_f_raster_colors((FCELL *) rast, colornum, n, colors) ;

<P>
If the <EM>data_type</EM> is DCELL_TYPE, calls
  D_lookup_d_raster_colors((DCELL *) rast, colornum, n, colors) ;

<P>
int D_lookup_c_raster_colors(CELL *cell, int *colornum, int n,
  struct Colors *colors) Same functionality as <TT>D_lookup_colors()</TT>
  except that the resultant color numbers are placed into a separate <EM>colornum</EM>
  array (which the caller must allocate) .

<P>
int D_lookup_f_raster_colors(FCELL *fcell, int *colornum, int n,
  struct Colors *colors) Same functionality as <TT>D_lookup_colors()</TT>
  except that the <EM>fcell</EM> array is type <TT>FCELL</TT> and that the resultant
  color numbers are placed into a separate <EM>colornum</EM> array (which the
  caller must allocate) .

<P>
int D_lookup_d_raster_colors(DCELL *dcell, int *colornum, int n,
  struct Colors *colors) Same functionality as <TT>D_lookup_colors()</TT>
  except that the <EM>dcell</EM> array is type <TT>DCELL</TT> and that the resultant
  color numbers are placed into a separate <EM>colornum</EM> array (which the
  caller must allocate) .

<P>
int D_draw_cell_of_type(int A_row, DCELL *xarray, struct Colors
  *colors, RASTER_MAP_TYPE map_type) If <EM>map_type</EM> is CELL_TYPE,
  calls D_draw_cell (A_row,(CELL *) xarray, colors) ;

<P>
If <EM>map_type</EM> is FCELL_TYPE, calls D_draw_f_cell (A_row,(FCELL *) 
  xarray, colors) ;

<P>
If <EM>map_type</EM> is DCELL_TYPE, calls D_draw_d_cell (A_row,(DCELL *) 
  xarray, colors) ;

<P>
int D_draw_f_cell (int A_row, FCELL *xarray, struct Colors
  *colors) Same functionality as <TT>D_draw_cell()</TT> except that the <EM>xarray</EM> 
  array is type <TT>FCELL</TT> which implies a call to <TT>D_f_raster()</TT> instead of a call to <TT>D_raster()</TT>.

<P>
int D_draw_d_cell (int A_row, DCELL *xarray, struct Colors
  *colors) Same functionality as <TT>D_draw_cell()</TT> except that the <EM>xarray</EM> 
  array is type <TT>DCELL</TT> which implies a call to <TT>D_d_raster()</TT> instead of a call to <TT>D_raster()</TT>.

<P>

\section New_functions_to_support_a_colors_for_the_NULL_value New functions to support a color for the NULL-value


<P>
int G_set_null_value_color (int r, int g, int b, struct Colors
  *colors) Sets the color (in <EM>colors</EM>) for the NULL-value to <EM>r,g,b</EM>.

<P>
int G_get_null_value_color (int *r, int *g, int *b, struct Colors
  *colors) Puts the red, green, and blue components of the color for the
  NULL-value into <EM>r,g,b</EM>.

<P>

\section New_functions_to_support_a_default_color New functions to support a default color


<P>
int G_set_default_color (int r, int g, int b, struct Colors
  *colors) Sets the default color (in <EM>colors</EM>) to <EM>r,g,b</EM>. This is
  the color for values which do not have an explicit rule.

<P>
int G_get_default_color (int *r, int *g, int *b, struct Colors
  *colors) Puts the red, green, and blue components of the
  <TT>"default"</TT> color into <EM>r,g,b</EM>.

<P>

\section New_functions_to_support_treating_a_raster_layer_as_a_color_image New functions to support treating a raster layer as a color image

<P>
int G_get_raster_row_colors(int fd, int row, struct Colors *colors,
  unsigned char *red, unsigned char *grn, unsigned char *blu,
  unsigned char *nul) Reads a row of raster data and converts it to red,
  green and blue components according to the <EM>colors</EM> parameter.

<P>
This provides a convenient way to treat a raster layer as a color
  image without having to explictly cater for each of <TT>CELL</TT>, <TT>  FCELL</TT> and <TT>DCELL</TT> types

<P>

\section Upgraded_color_functions Upgraded color functions

<P>
int G_read_colors() This routine reads the rules from the color
  file. If the input raster map is is a floating-point map it calls <TT>G_mark_colors_as_fp()</TT>.

<P>
int G_write_colors() The rules are written out using
  floating-point format, removing trailing zeros (possibly producing integers) .
  The flag marking the colors as floating-point is <B>not</B> written.

<P>
int G_get_colors_min_max() If the color table is marked as
  <TT>"float"</TT>, then return the minimum as -(255&#94;3 * 128) and the maximum
  as (255&#94;3 * 128).
 This is to simulate a very <B>large</B> range so that
  GRASS doesn't attempt to use <EM>colormode float</EM> to allow interactive
  toggling of colors.

<P>
int G_lookup_colors() Modified to return a color for NULL-values.

<P>
int G_get_color() Modified to return a color for the NULL-value.

<P>

\section Changes_to_the_Colors_structure Changes to the <TT>Colors</TT> structure

<P>
Modifications to the <TT>Colors</TT> structure to support colors for floating-point data and
the NULL-value consist of

<P>

<UL>
<LI>the _Color_Rule_ struct was changed to have DCELL value (instead of
  CELL cat) to have the range be floating-point values instead of integer cats.
</LI>
<LI>a color for NULL was added
</LI>
<LI>the special color for zero was eliminated
</LI>
<LI>a default color for values which have no assigned color was added
</LI>
<LI>a flag was added to the Colors structure to indicate if either the map
  itself is floating-point (If the map is integer and the floating point
  functions are used to lookup colors, the values are checked to see if they
  are integer, and if they are, the integer mechanism is used) 
</LI>
<LI>fp_lookup - a lookup table for floating point numbers is added. It
  orders the end points of fp intervals into array with a pointer to a color
  rule for each inteval, and the binary search is then used when looking up
  colors instead of linearly searching through all color rules.
</LI>
</UL>

<P>

\section Changes_to_the_colr_file Changes to the <TT>colr</TT> file

<UL>
<LI>The rules are written out using floating-point format, removing trailing
  zeros (possibly producing integers) . For example, to ramp from red to green
  for the range [1.3,5.0]:
<PRE>
            1.3:255:0:0  5:0:255:0
</PRE>
</LI>
<LI>The NULL-value color is written as:
<PRE>
            nv:red:grn:blu
</PRE>
</LI>
<LI>The default color (for values that don't have an explicit rule) is written
as:
<PRE>
            *:red:grn:blu
</PRE>
</LI>
</UL>

<P>

\section Range_functions Range functions (new and upgraded)

\subsection Modified_range_functions Modified range functions


<P>
int G_read_range() Old range file (those with 4 numbers) should
  treat zeros in this file as NULL-values. New range files (those with just 2
  numbers) should treat these numbers as real data (zeros are real data in this
  case) .

<P>
An empty range file indicates that the min, max are undefined. This is a
  valid case, and the result should be an initialized range struct with no
  defined min/max.

<P>
If the range file is missing and the map is a floating-point map, this
  function will create a default range by calling <TT>G_construct_default_range()</TT>.

<P>
int G_init_range() Must set a flag in the range structure that indicates that
  no min/max have been defined - probably a <TT>"first"</TT> boolean flag.

<P>
int G_update_range() NULL-values must be detected and ignored.

<P>
int G_get_range_min_max() If the range structure has no defined min/max
  (first!=0) there will not be a valid range. In this case the min and max returned must
  be the NULL-value.

<P>
int G_write_range() This routine only writes 2 numbers (min,max) to the range
  file, instead of the 4 (pmin,pmax,nmin,nmax) previously written. If there is no defined
  min,max, an empty file is written.

<P>

\section New_range_functions New range functions


<P>
int G_construct_default_range(struct Range *r) Sets the integer
  range <EM>r</EM> to [1,255]

<P>
int G_read_raster_range(void *r, char *name, char *mapset,
  RASTER_MAP_TYPEmap_type) If <EM>map_type</EM> is CELL_TYPE, calls
  G_read_range((struct Range *) r, name, mapset) ; otherwise calls
  G_read_fp_range((struct FPRange *) r, name, mapset) ;

<P>
int G_read_fp_range(struct FPRange *r, char *name, char
  *mapset) Read the floating point range file <TT>f_range</TT>. This file is
  written in binary using XDR format. If there is no defined min/max in <EM>r</EM>, 
  an empty <TT>f_range</TT>file is created.

<P>
An empty range file indicates that the min, max are undefined. This is a
  valid case, and the result should be an initialized range struct with no
  defined min/max.

<P>
If the range file is missing and the map is a floating-point map, this
  function will create a default range by calling <TT>G_construct_default_range()</TT>.

<P>
int G_init_raster_range (FPRange *r, RASTER_MAP_TYPE
  map_type) If <EM>map_type</EM> is CELL_TYPE, calls G_init_range(struct
  Range *) r) ; otherwise calls G_init_fp_range((struct FPRange *) r) ;

<P>
int G_init_fp_range (FPRange *r) Must set a flag in the range
  structure that indicates that no min/max have been defined - probably a
  <TT>"first"</TT> boolean flag.

<P>
int G_update_f_range (FPRange *r, FCELL *fcell, int n) Updates the
floating-point range <EM>r</EM> from the <EM>n</EM> <TT>FCELL</TT> values in <EM>fcell</EM>
NULL-values must be detected and ignored.

<P>
int G_update_d_range (FPRange *r, DCELL *dcell, int n) Updates
  the floating-point range <EM>r</EM> from the <EM>n</EM> <TT>DCELL</TT> values in 
  <EM>dcell</EM> NULL-values must be detected and ignored.

<P>
int G_get_fp_range_min_max (FPRange *r, DCELL *min, DCELL
  *max) Extract the min/max from the range structure <EM>r</EM>.

<P>
If the range structure has no defined min/max (first!=0) there will not be a
  valid range. In this case the min and max returned must be the NULL-value.

<P>
int G_write_fp_range (FPRange *r) Write the floating point range
  file <TT>f_range</TT>. This file is written in binary using XDR format. If
  there is no defined min/max in <EM>r</EM>, an empty <TT>f_range</TT>file is
  created.

<P>

\section New_and_Upgraded_Cell_stats_functions New and Upgraded Cell_stats functions


<P>
Modified <TT>Cell_stats</TT> functions to handle NULL-values:

<P>
int G_init_cell_stats() Set the count for NULL-values to zero.

<P>
int G_update_cell_stats() Look for NULLs and update the
  NULL-value count.

<P>
int G_next_cell_stat() Do not return a record for the
  NULL-value

<P>
int G_find_cell_stat() Allow finding the count for the
  NULL-value

<P>
int G_get_stats_for_null_value(int *count, struct Cell_stats
  *s) Get a number of null values from stats structure. Note: when reporting
  values which appear in a map using G_next_cell_stats() , to get stats for
  null, call G_get_stats_for_null_value() first, since
  G_next_cell_stats() does not report stats for null.

<P>

\section New_Quantization_Functions New Quantization Functions


<P>
New functions to support quantization of floating-point to integer:

<P>
int G_write_quant(char *name, char *mapset, struct Quant
  *q) Writes the <TT>f_quant</TT> file for the raster map <EM>name</EM> from <EM>q</EM>.

<P>
if mapset==G_mapset() i.e. the map is in current mapset, then the original
  quant file in cell_misc/map/f_quant is written. Otherwise <EM>q</EM> is
  written into quant2/mapset/name (much like colr2 element) . This results in
  map&#64;mapset being read using quant rules stored in <EM>q</EM> from
  G_mapset() .  See G_read_quant() for detailes.

<P>
int G_set_quant_rules (int fd, struct Quant *q) Sets quant
  translation rules for raster map opened for reading. fd is a file descriptor
  returned by G_open_cell_old() . After calling this function,
  G_get_c_raster_row() and G_get_map_row() will use rules defined by q
  (instead of using rules defined in map's quant file) to convert floats to
  ints.

<P>
int G_read_quant(char *name, char *mapset, struct Quant *q) reads
  quantization rules for <TT>"name"</TT> in <TT>"mapset"</TT> and stores them
  in the quantization structure <TT>"quant"</TT>. If the map is in another
  mapset, first checks for quant2 table for this map in current mapset.

<P>
Return codes:

<P>
-2 if raster map is of type integer

<P>
-1 if (! G__name_is_fully_qualified () ) 

<P>
0 if quantization file does not exist, or the file is empty or has wrong
  format.

<P>
1 if non-empty quantization file exists.

<P>
int G_quant_init(struct Quant *q) Initializes the <EM>q</EM>
  struct.

<P>
int G_quant_free(struct Quant *q) Frees any memory allocated in
  <EM>q</EM> and re-initializes <EM>q</EM> by calling <TT>G_quant_init()</TT>.

<P>
int G_quant_truncate(struct Quant *q) sets the quant for <EM>q</EM>
  rules to perform simple truncation on floats.

<P>
int G_quant_truncate(struct Quant *q) sets the quant for <EM>q</EM>
  rules to perform simple rounding on floats.

<P>
int G_quant_organize_fp_lookup(struct Quant *quant) Organizes
  fp_lookup table for faster (logarithmic) lookup time
  G_quant_organize_fp_lookup() creates a list of min and max for each quant
  rule, sorts this list, and stores the pointer to quant rule that should be
  used inbetween any 2 numbers in this list Also it stores extreme points for 2
  infinite rules, if exist After the call to G_quant_organize_fp_lookup() 
  instead of linearly searching through list of rules to find a rule to apply,
  quant lookup will perform a binary search to find an interval containing
  floating point value, and then use the rule associated with this interval.
  when the value doesn't fall within any interval, check for the infinite
  rules.

<P>
int G_quant_add_rule(struct Quant *q, DCELL dmin, DCELL dmax, CELL
  cmin, CELL cmax) Add the rule that the floating-point range <EM>[dmin,dmin]</EM>
   produces an integer in the range <EM>[cmin,cmax]</EM> by linear interpolation.

<P>
Rules that are added later have higher precedence when searching.

<P>
If any of of <EM>dmin</EM>, <EM>dmax</EM> <EM>cmin</EM>, or <EM>cmax</EM> is the
  NULL-value, this rule is not added and 0 is returned. Otherwise return 1. if
  the fp_lookup is organized, destroy it.

<P>
int G_quant_set_positive_infinite_rule(struct Quant *q, DCELL
  dmax, CELL c) Set the rule that values greater than or equal to <EM>dmax</EM> 
  produce the integer <EM>c</EM>.  If <EM>dmax</EM> or <EM>c</EM> is the
  NULL-value, return 0 and don't set the rule. Otherwise return 1.

<P>
This rule has lower precedence than rules added with <TT>G_quant_add_rule()</TT>.

<P>
int G_quant_get_positive_infinite_rule(struct Quant *q, DCELL
  *dmax, CELL *c) Sets <EM>dmax</EM> and <EM>c</EM> to the positive
  <TT>"infinite"</TT> rule in <EM>q</EM> if there is one and returns 1. If there
  is no such rule, it just returns 0. if the fp_lookup is organized, updates
  infinite limits.

<P>
int G_quant_set_negative_infinite_rule(struct Quant *q, DCELL
  dmin, CELL c) Set the rule that values less than or equal to <EM>dmin</EM>
  produce the integer <EM>c</EM>. If <EM>dmin</EM> or <EM>c</EM> is the NULL-value,
  return 0 and don't set the rule. Otherwise return 1. if the fp_lookup is
  organized, updates infinite limits.

<P>
This rule has lower precedence than rules added with <TT>  G_quant_add_rule()</TT>.

<P>
int G_quant_get_negative_infinite_rule(struct Quant *q, DCELL
  *dmin, CELL *c) Sets <EM>dmin</EM> and <EM>c</EM> to the negative
  <TT>"infinite"</TT> rule in <EM>q</EM> if there is one and returns 1. If there
  is no such rule, it just returns 0.

<P>
int G_quant_get_limits(struct Quant *q, DCELL *dmin, DCELL *dmax,
  CELL *cmin, CELL *cmax) Extracts the minimum and maximum floating-point
  and integer values from all the rules (except the <TT>"infinite"</TT> rules) 
  in <EM>q</EM> into <EM>dmin</EM>, <EM>dmax</EM>, <EM>cmin</EM>, and <EM>cmax</EM>. Returns 1
  if there are any explicit rules. If there are no explicit rules, (this
  includes cases when q is set to truncate or round map) , it returns 0 and sets
  <EM>dmin</EM>, <EM>dmax</EM>, <EM>cmin</EM>, and <EM>cmax</EM> to NULL.

<P>
int G_quant_nrules(struct Quant *q) Returns the number of rules
  in <EM>q</EM>, excluding the negative and positive <TT>"infinite"</TT> rules.

<P>
int G_quant_get_rule(struct Quant *q, int n, DCELL *dmin, DCELL
  *dmax, CELL *cmin, CELL *cmax) Get the <EM>n</EM>th rule from <EM>q</EM>. If 0
  &lt;= <EM>n</EM> &lt; nrules(q) , extract the rule and return 1.
  Otherwise return 0. This function can't be used to get the
  <TT>"infinite"</TT> rules.

<P>
The order of the rules returned by increasing <EM>n</EM> is the order in which
  the rules are applied when quantizing a value - the first rule applicable is
  used.

<P>
CELL G_quant_get_cell_value(struct Quant *q, DCELL value) 
  Returns a CELL category for the floating-point <EM>value</EM> based on the
  quantization rules in <EM>q</EM>. The first rule found that applies is used.
  The rules are searched in the reverse order they are added to <EM>q</EM>.  If no
  rule is found, the <EM>value</EM> is first tested against the negative infinite
  rule, and finally against the positive infinite rule. if none of these rules
  apply, the NULL-value is returned.

<P>
<B>NOTE.</B> See G_quant_organize_fp_lookup() for details on how the
  values are looked up from fp_lookup table when it is active. (Right now
  fp_lookup is automatically organized during the first call to
  G_quant_get_cell_value() 

<P>
int G_quant_perform_d(struct Quant *q, DCELL *dcell, CELL *cell,
  int n) Performs a quantization of the <EM>n</EM> <TT>DCELL</TT> values in the
  <EM>dcell</EM> array and puts the results into the <EM>cell</EM> array.

<P>
int G_quant_perform_f(struct Quant *q, FCELL *fcell, CELL *cell,
  int n) Performs a quantization of the <EM>n</EM> <TT>FCELL</TT> values in the
  <EM>fcell</EM> array and puts the results into the <EM>cell</EM> array.

<P>
These next two functions are convenience functions to allow applications to
easily create quantization rules other than the defaults:

<P>
int G_quantize_fp_map(char *name, CELL cmin, CELL cmax) Writes
  the <TT>f_quant</TT> file for the raster map <EM>name</EM> with one rule. The rule
  is generated using the floating-point range in <TT>f_range</TT> producing the
  integer range [<EM>cmin,cmax</EM>].

<P>
int G_quantize_fp_map_range(char *name, DCELL dmin, DCELL dmax,
  CELL cmin, CELL cmax) Writes the <TT>f_quant</TT> file for the raster map
  <EM>name</EM> with one rule. The rule is generated using the floating-point
  range [<EM>dmin,dmax</EM>] and the integer range
  [<EM>min,max</EM>].

<P>
This routine differs from the one above in that the application controls the
  floating-point range. For example, r.slope.aspect will use this routine to
  quantize the slope map from [0.0, 90.0] to [0,
  90] even if the range of slopes is not 0-90. The aspect map would be
  quantized from [0.0, 360.0] to [0, 360].

<P>

\section Categories_Labeling_Functions Categories Labeling Functions (new and upgraded)

\subsection Upgraded_Categories_structure Upgraded Categories structure


<P>
All the new programs which are using Categories structure directly have to be
modified to use API functions to update and retrieve info from Categories
structure. Both new and old API function can be used, since old functions still
have exact same functionality (even though internally they are implemented very
differently) .  New function names end with raster_cats() ; old function names
end with _cats() .
<BR>
<P>
We made sure that all old fields in Categories structure are either missing in
new Categories structure or have exactly the same meaning. We did it so that
the modules using Categories structure directly either do not compile with new
gis library or work exactly the same as bnefore.  A programmer might want to
read the data in a floating point map in a way that each cell value stores
index of it's category label and data range.  The way to do it is to call
G_set_quant_rules(fd, &amp;pcats-&gt;q) after openning the map.
<BR>
<P>
This is helpful when trying to collect statistics (how many cells of each
category are in the map. (although there is another new mechanism to collect
such stats - see G_mark_raster_cats() ) . Another reason to get a category
index instead of fp values is that this index will be the FID into GRASS-DBMS
link. Also he can use G_get_ith_raster_cat() to get the category
information for each cell using this index.
<BR>
<P>
Here is the new Categories structure defined in <TT>"gis.h"</TT>:

<P>
\verbatim
struct Categories
{
    CELL ncats            ;   /* total number of categories              */
    CELL num              ;   /* the highest cell values. Only exists
                                 for backwards compatibility = (CELL)
                                 max_fp_values in quant rules            */
    char *title           ;   /* name of data layer                      */
    char *fmt             ;   /* printf-like format to generate labels   */
    float m1              ;   /* Multiplication coefficient 1            */
    float a1              ;   /* Addition coefficient 1                  */
    float m2              ;   /* Multiplication coefficient 2            */
    float a2              ;   /* Addition coefficient 2                  */
    struct Quant q        ;   /* rules mapping cell values to index in
                                 list of labels                          */
    char **labels         ;   /* array of labels of size num             */
    int * marks           ;   /* was the value with this label was used? */
    int nalloc;
    int last_marked_rule  ;
} ;

\endverbatim
<P>

\section Changes_to_the_cats_file Changes to the <TT>cats</TT> file


<P>
The format of explicit label entries is the same for integer maps.
<PRE>
    cat:description
</PRE>
In addition label entries of new format is supported for floating point maps.
<PRE>
    val:descr (where val is a floating point number) 
</PRE>
or
<PRE>
    val1:val2:descr (where val1, val2 is a floating point range) 
</PRE>

<P>
Internally the labels are stored for fp ranges of data. However when the cats
file is written, all the decimal zeros are stripped so that integer values
appear as integers in the file. Also if values are the same, only 1 value is
written (i.e. first format) .
<BR>
<P>
This way even though the old cats files will be processed differently
internally, the user or application programmer will not notice this difference
as long as the proper api is used and the elements of Categories structure are
not accessed directly without API calls.

<P>

\section Range_functions Range functions (new and upgraded)


<P>

\section New_Functions_to_read_write_access_and_modify_Categories_structure New Functions to read/write access and modify Categories structure

<P>
int G_read_raster_cats(char *name, *mapset, struct Categories
  *pcats) Is the same as existing G_read_cats() 

<P>
int G_copy_raster_cats(struct Categories *pcats_to, struct
  Categories*pcats_from) Allocates NEW space for quant rules and labels n
  <EM>pcats_to</EM> and copies all info from <EM>pcats_from</EM> cats to <EM>pcats_to</EM> cats.

<P>
returns:

<P>
0 if successful

<P>
-1 on fail

<P>
char * G_get_raster_cat(void *val, struct Categories *pcats,
  RASTER_MAP_TYPE data_type) given a raster value <EM>val</EM> of type <EM>data_type</EM> 
  Returns pointer to a string describing category.

<P>
char * G_get_c_raster_cat(CELL *val, struct Categories *pcats) 
  given a CELL value <EM>val</EM> Returns pointer to a string describing
  category.

<P>
char * G_get_d_raster_cat(DCELL *val, struct Categories
  *pcats) given a DCELL value <EM>val</EM> Returns pointer to a string
  describing category.

<P>
char * G_get_f_raster_cat(FCELL *val, struct Categories
  *pcats) given a FCELL value <EM>val</EM> Returns pointer to a string
  describing category.

<P>
int G_set_raster_cat(void *rast1, void *rast2, struct Categories
  *pcats, RASTER_MAP_TYPE data_type) Adds the label for range <EM>rast1</EM> through 
  <EM>rast2</EM> in category structure <EM>pcats</EM>.

<P>
int G_set_c_raster_cat(CELL *rast1, CELL *rast2, struct Categories
  *pcats) Adds the label for range <EM>rast1</EM> through <EM>rast2</EM> in
  category structure <EM>pcats</EM>.

<P>
int G_set_f_raster_cat(FCELL *rast1, FCELL *rast2, struct
  Categories *pcats) Adds the label for range <EM>rast1</EM> through <EM>rast2</EM>
in category structure <EM>pcats</EM>.

<P>
int G_set_d_raster_cat(DCELL *rast1, DCELL *rast2, struct
  Categories *pcats) Adds the label for range <EM>rast1</EM> through <EM>rast2</EM>
in category structure <EM>pcats</EM>.

<P>
int * G_number_of_raster_cats (pcats) Returns the number of
  labels. DO NOT use G_number_of_cats() (it returns max cat number) 

<P>
char * G_get_ith_raster_cat(struct Categories *pcats, int i, void
  *rast1, void *rast2, RASTER_MAP_TYPE data_type) Returns i-th
  description and i-th data range from the list of category descriptions with
  corresponding data ranges. Stores end points of data interval in <EM>rast1</EM>
  and <EM>rast2</EM> (after converting them to <EM>data_type</EM>.

<P>
char * G_get_ith_c_raster_cat(struct Categories *pcats, int i,
  CELL *rast1, CELL *rast2) Returns i-th description and i-th data range
  from the list of category descriptions with corresponding data ranges. end
  points of data interval in <EM>rast1</EM> and <EM>rast2</EM>.

<P>
char * G_get_ith_f_raster_cat(struct Categories *pcats, int i,
  FCELL *rast1, FCELL *rast2) Returns i-th description and i-th data range
  from the list of category descriptions with corresponding data ranges. end
  points of data interval in <EM>rast1</EM> and <EM>rast2</EM>.

<P>
char * G_get_ith_d_raster_cat(struct Categories *pcats, int i,
  DCELL *rast1, DCELL *rast2) Returns i-th description and i-th data range
  from the list of category descriptions with corresponding data ranges. end
  points of data interval in <EM>rast1</EM> and <EM>rast2</EM>.

<P>
char * G_get_raster_cats_title(struct Categories
  *pcats) Returns pointer to a string with title.

<P>
int G_unmark_raster_cats(struct Categories *pcats) Sets marks
  for all categories to 0. This initializes Categories structure for subsequest
  calls to G_mark_raster_cats (rast_row,...) for each row of data, where
  non-zero mark for i-th label means that some of the cells in rast_row are
  labeled with i-th label and fall into i-th data range.

<P>
These marks help determine from the Categories structure which labels were
  used and which weren't.

<P>
int G_get_next_marked_raster_cat(struct Categories *pcats, void
  *rast1, void *rast2, long *stats, RASTER_MAP_TYPE data_type) Finds the
  next label and corresponding data range in the list of marked categories. The
  category (label + data range) is marked by G_mark_raster_cats () . End
  points of the data range are converted to <EM>data_type</EM> and returned in
  rast1, rast2. the number of times value from i-th cat. data range appeared so
  far is returned in stats. See G_unmark_raster_cats() ,
  G_rewind_raster_cats() and G_mark_raster_cats () .

<P>
int G_get_next_marked_c_raster_cat(struct Categories *pcats, CELL
  *rast1, CELL *rast2, long *stats) Finds the next label and corresponding
  data range in the list of marked categories. The category (label + data
  range) is marked by G_mark_raster_cats () . End points of the data range
  are converted to <EM>data_type</EM> and returned in rast1, rast2. the number of
  times value from i-th cat. data range appeared so far is returned in stats.
  See G_unmark_raster_cats() , G_rewind_raster_cats() and
  G_mark_raster_cats () .

<P>
int G_get_next_marked_f_raster_cat(struct Categories *pcats,
  FCELL *rast1, FCELL *rast2, long *stats) Finds the next label and
  corresponding data range in the list of marked categories. The category
  (label + data range) is marked by G_mark_raster_cats () . End points of the
  data range are converted to <EM>data_type</EM> and returned in rast1, rast2.
  the number of times value from i-th cat. data range appeared so far is
  returned in stats. See G_unmark_raster_cats() , G_rewind_raster_cats() 
  and G_mark_raster_cats () .

<P>
int G_get_next_marked_d_raster_cat(struct Categories *pcats,
  DCELL *rast1, DCELL *rast2, long *stats) Finds the next label and
  corresponding data range in the list of marked categories. The category
  (label + data range) is marked by G_mark_raster_cats () . End points of the
  data range are converted to <EM>data_type</EM> and returned in rast1, rast2.
  the number of times value from i-th cat. data range appeared so far is
  returned in stats. See G_unmark_raster_cats() , G_rewind_raster_cats() 
  and G_mark_raster_cats () .

<P>
int G_mark_raster_cats(void *rast_row, int ncols, struct
  Categories *pcats, RASTER_MAP_TYPE data_type) Looks up the category
  label for each raster value in the <EM>rast_row</EM> (row of raster cell value) 
  and updates the marks for labels found.

<P>
NOTE: non-zero mark for i-th label stores the number of of raster cells read
  so far which are labeled with i-th label and fall into i-th data range.

<P>
int G_mark_c_raster_cats(CELL *rast_row, int ncols, struct
  Categories *pcats) Looks up the category label for each raster value in
  the <EM>rast_row</EM> and updates the marks for labels found.

<P>
NOTE: non-zero mark for i-th label stores the number of of raster cells read
  so far which are labeled with i-th label and fall into i-th data range.

<P>
int G_mark_f_raster_cats(FCELL *rast_row, int ncols, struct
  Categories *pcats) Looks up the category label for each raster value in
  the <EM>rast_row</EM> and updates the marks for labels found.

<P>
NOTE: non-zero mark for i-th label stores the number of of raster cells read
  so far which are labeled with i-th label and fall into i-th data range.

<P>
int G_mark_d_raster_cats(DCELL *rast_row, int ncols, struct
  Categories *pcats) Looks up the category label for each raster value in
  the <EM>rast_row</EM> and updates the marks for labels found.

<P>
NOTE: non-zero mark for i-th label stores the number of of raster cells read
  so far which are labeled with i-th label and fall into i-th data range.

<P>
int G_rewind_raster_cats(struct Categories *pcats) after call to
  this function G_get_next_marked_raster_cat() returns the first marked
  cat label.

<P>
int G_init_raster_cats(char *title, struct Categories
  *pcats) Same as existing G_init_raster_cats() only ncats argument is
  missign. ncats has no meaning in new Categories structure and only stores
  (int) largets data value for backwards compatibility.

<P>
int G_set_raster_cats_fmt(char *fmt, float m1, a1, m2, a2, struct
  Categories*pcats) Same as existing G_set_cats_fmt() 

<P>
int G_set_raster_cats_title(char *title, struct Categories
  *pcats) Same as existing G_set_cats_title() 

<P>
int G_write_raster_cats(char *name, struct Categories
  *pcats) Same as existing G_write_cats() 

<P>
int G_free_raster_cats(struct Categories *pcats) Same as
  existing G_free_cats() 

<P>

\section Library_Functions_that_are_Deprecated Library Functions that are Deprecated


<P>
These functions are deprecated, since they imply that the application that uses
them has not been upgraded to handle NULL-values and should be eliminated from
GRASS code.

<P>

<UL>
<LI><TT>G_get_map_row()</TT>:

<P>
To be replaced by <TT>G_get_c_raster_row()</TT>.
</LI>
<LI><TT>G_get_map_row_nomask()</TT>:

<P>
To be replaced by <TT>G_get_c_raster_row_nomask()</TT>.
</LI>
<LI><TT>G_put_map_row()</TT>:

<P>
To be replaced by <TT>G_put_c_raster_row()</TT>.
</LI>
</UL>


<P>
These functions are deprecated, since they can not be upgraded to support
NULL-values, and should be eliminated from GRASS code.

<P>

<UL>
<LI><TT>G_open_map_new_random()</TT>
</LI>
<LI><TT>G_put_map_row_random()</TT>
</LI>
</UL>

<P>
<B>Also, no support for random writing of floating-point rasters will be provided.</B>

<P>

\section Guidelines_for_upgrading_GRASS_4_x_Modules Guidelines for upgrading GRASS 4.x Modules


<P>

<UL>
<LI>Modules that process raster maps as <EM>continuous</EM> data should read
  raster maps as floating-point. Modules that process raster maps as <EM>nominal</EM> data
  should read raster maps as integer.
<BR>

<P>
<EM>Exception:</EM> Modules that process raster colors or the modules which
  report on raster categories labels should either always read the maps as
  floating-point, or read the maps as integer if the map is integer and
  floating-point if the map is floating-point.
</LI>
<LI>The quantization of floating-point to integer should NOT change the color
  table. The color lookup should have its own separate quantization.
</LI>
<LI>The quantization of floating-point to integer should NOT change the
  Categories table. The Categories structure should have its own separate
  quantization.
</LI>
<LI>Modules that read or write floating-point raster maps should use <TT>double</TT>
(<TT>DCELL</TT>) arrays instead of <TT>float</TT> (<TT>FCELL</TT>) arrays.
</LI>
<LI>Modues should process NULL values in a well defined (consistent) manner.
  Modules that processed zero as the pseudo NULL-value should be changed to use
  the true NULL-value for this and process zero as normal value.
</LI>
<LI>Modules should process non-NULL values as normal numbers and not treat
  any particular numbers (e.g. zero) as special.
</LI>
</UL>

<P>

\section Important_hints_for_upgrades_to_raster_modules Important hints for upgrades to raster modules


<P>
In general modules that use <TT>G_get_map_row()</TT>. should use <TT>  G_get_c_raster_row()</TT> instead.

<P>
Modules that use <TT>G_put_map_row()</TT>. should use <TT>  G_put_c_raster_row()</TT> instead.

*/