Geografic-Information-System/scripts/d.rast.edit/d.rast.edit.html

<h2>DESCRIPTION</h2>

The <em>d.rast.edit</em> program allows users to interactively
edit cell category values in a raster map layer displayed to the
graphics monitor using a mouse cursor.


<h2>USAGE</h2>

<b><I>Note: this help page refers to the old Tcl/Tk version of this
program. Parts of it may be out of date or wrong.</I></b>


<h3>Overview window</h3>

An overview window shows the entire map with a box showing the current
editing region. The edit window shows the cells within the selected area.
Click on a new spot on the overview window to move the editing area.
Moving the editing view can take a while.

<h3>Mouse and menus</h3>

Cell editing is done using a mouse cursor to choose menu selections
and indicate areas on the displayed raster map that are to be edited.

<p>Selections available at the top of the edit window are <b>Save</b> and
<b>Exit</b>.
<p>
As the mouse travels over the cells in the edit window you are shown the
current coordinates and current cell values under the cursor.
<p>To change the value of a cell put the new value to use in the "New value"
box at the bottom left of the edit window under the coordinate information
bar. A value of "*" indicates a NULL value should be used.


<h3>Arrows</h3>

This function is available for users editing aspect maps.  The
<em><a href="d.rast.arrow.html">d.rast.arrow</a></em> program is
called, which draws arrows over the displayed
cells to indicate the downslope direction of the cell.
You can set the aspect map to use on the command line.
Aspect maps are expected to be in regular "GRASS" format, as produced by
<em><a href="r.slope.aspect.html">r.slope.aspect</a></em>; i.e. degrees
counter-clockwise from east.


<h2>NOTES</h2>

There is no "undo" command or way to exit edit mode without saving
changes.
<p>Any MASK in place will be respected when writing the new raster map layer,
including any edits to the MASKed areas.

<h3>Geographic Region Concerns</h3>

<em>d.rast.edit</em> reads the region definition for the raster map layer
being edited from its internal cell header file. The new, edited copy of
the raster layer will be created with the same resolution and region
dimensions.
<p>The primary bane of the <em>d.rast.edit</em> program involves large map
layers with lots of rows and columns) and/or slow computers,
since the program must read and write raster map layers row by row for
the full size of the map layer as dictated by its region size and resolution.
(The current region settings of north, south, east, and west
will not limit the size of the edited copy of the map layer,
since by use of the overview selection these values may change several
times during the editing session).


<h2>TODO</h2>

<!-- not true, but it would be nice
<em>d.rast.edit</em> will not create a new raster map layer if
the user makes no cell edits while running the program.
<p>-->

It would be nice to incorporate a scrollable version of <em>
<a href="d.legend.html">d.legend</a>
</em>
(such that one could see a label legend for files with many categories on
a standard size sub-frame).  It would be even nicer to be able
to select the category values from a graphical legend when editing
cell values (thereby saving a trip to the text frame to type in the
new value).

<p>Perhaps method(s) for multiple  or mass cell edits would be useful.
This could be done by providing modes in which the user may:
<ol>
<li> edit a block of cells to a given value by drawing a box;</li>
<li> be able to choose a given value which is automatically used as
the new value on each cell chosen until a different value is desired.</li>
</ol>

<p>There is no interrupt handling. <!-- ?? --> This could leave files in .tmp
or (rarely) result in half-baked raster maps.  The original file
would survive unscathed by an interrupt at most any point in execution.
Beware of exiting the program
by means other than using <em>exit</em> on the <em>Main Menu</em>.


<h2>SEE ALSO</h2>

<em>
<a href="d.rast.arrow.html">d.rast.arrow</a>,
<a href="d.rast.num.html">d.rast.num</a>
</em>

<h2>AUTHOR</h2>

Tcl/Tk and wxPython versions: Glynn Clements<br>
<br>
Replaces Xdriver version in C by Chris Rewerts,
Agricultural Engineering,
Purdue University

<p><i>Last changed: $Date$</i>