raster library: Added a function to convert a raster map to unsigned char array that represent a

32bit ARGB or 8bit gray scale image. This function is used by pygrass to very fast 
create image representations out of raster map layers at different resolutions
to be used by PyQt4 or Wx based canvas that support zoom and pan or time series animation.


git-svn-id: https://svn.osgeo.org/grass/grass/trunk@66070 15284696-431f-4ddb-bdfa-cd5b030d7da7

include/defs/raster.h

@@ -544,6 +544,9 @@ char *Rast_read_vdatum(const char *, const char *);
 void Rast_write_units(const char *, const char *);
 void Rast_write_vdatum(const char *, const char *);
 
+/* rast_to_img_string.c */
+int Rast_map_to_img_str(char *, int, unsigned char*);
+
 /* reclass.c */
 int Rast_is_reclass(const char *, const char *, char *, char *);
 int Rast_is_reclassed_to(const char *, const char *, int *, char ***);

lib/raster/rast_to_img_string.c

@@ -0,0 +1,166 @@
+
+/****************************************************************************
+ *
+ * Function:     Rast_map_to_img_str() based on r.to.ppm
+ * AUTHOR(S):    Bill Brown, USA-CERL (original contributor)
+ *               Markus Neteler <neteler itc.it>, 
+ *               Bernhard Reiter <bernhard intevation.de>, 
+ *               Glynn Clements <glynn gclements.plus.com>, 
+ *               Jachym Cepicky <jachym les-ejk.cz>, 
+ *               Jan-Oliver Wagner <jan intevation.de>
+ *               Soeren Gebbert
+ * PURPOSE:      converts a GRASS raster map into an ARGB or
+ *               gray scale unsigned char string
+ * COPYRIGHT:    (C) 1999-2015 by the GRASS Development Team
+ *
+ *               This program is free software under the GNU General Public
+ *               License (>=v2). Read the file COPYING that comes with GRASS
+ *               for details.
+ *
+ *****************************************************************************/
+
+#include <string.h>
+#include <stdlib.h>
+
+#include <grass/gis.h>
+#include <grass/raster.h>
+#include <grass/glocale.h>
+
+#define DEF_RED 255
+#define DEF_GRN 255
+#define DEF_BLU 255
+
+/* \brief Convert a raster map layer into a string with
+ *        32Bit ARGB or 8Bit Gray little endian encoding.
+ * 
+ * The raster color table is used for coloring the image. Null values are 
+ * marked as transparent. Only little endian encoding is supported.
+ * 
+ * This function uses Rast_window_rows() and Rast_window_cols() to 
+ * get rows and cols, hence use Rast_set_window() to set the required
+ * region for raster access.
+ * 
+ * \param name The name of the raster map layer to convert
+ * \param color_mode The color mode to use (1 -> 32Bit ARGB, 2 or 3 -> 8Bit Gray)
+ *          
+ *                  Color mode 2 -> grey scale formular: .33R+ .5G+ .17B
+ *                  Color mode 3 -> grey scale formular: .30R+ .59G+ .11B
+ * 
+ * \param result: An unsigned char pointer to store the result. 
+ *                It must have size 4*cols*rows in case of
+ *                ARGB and rows*cols in case of gray scale.
+ * 
+ * \return: 0 in case map not found, 1 on success
+ * 
+ */
+int Rast_map_to_img_str(char *name, int color_mode, unsigned char* result)
+{
+    unsigned char *set = NULL, *red = NULL, *green = NULL, 
+                  *blue = NULL;
+    unsigned char alpha;
+    const char *mapset = NULL;
+    CELL *cell_buf = NULL;
+    FCELL *fcell_buf = NULL;
+    DCELL *dcell_buf = NULL;
+    void *voidc = NULL;
+    int rtype, row, col;
+    size_t i;
+    int map = 0;
+    
+    struct Colors colors;
+    int rows = Rast_window_rows();
+    int cols = Rast_window_cols();
+
+    mapset = G_find_raster2(name, "");
+    
+    if(!mapset)
+        return(0);
+    
+    map = Rast_open_old(name, "");
+
+    cell_buf = Rast_allocate_c_buf();
+    fcell_buf = Rast_allocate_f_buf();
+    dcell_buf = Rast_allocate_d_buf();
+
+    red = G_malloc(cols);
+    green = G_malloc(cols);
+    blue = G_malloc(cols);
+    set  = G_malloc(cols);
+
+    Rast_read_colors(name, mapset, &colors);
+
+    rtype = Rast_get_map_type(map);
+    if (rtype == CELL_TYPE)
+        voidc = (CELL *) cell_buf;
+    else if (rtype == FCELL_TYPE)
+        voidc = (FCELL *) fcell_buf;
+    else if (rtype == DCELL_TYPE)
+        voidc = (DCELL *) dcell_buf;
+
+    i = 0;
+    
+    if(color_mode == 1) {/* 32BIT ARGB COLOR IMAGE with transparency */
+        for (row = 0; row < rows; row++) {
+            Rast_get_row(map, (void *)voidc, row, rtype);
+            Rast_lookup_colors((void *)voidc, red, green, blue, set,
+                               cols, &colors, rtype);
+                               
+            alpha = (unsigned char)255;
+            if ( Rast_is_null_value( voidc, rtype ) )
+            {
+                alpha = (unsigned char)0;
+            }
+            for (col = 0; col < cols; col++) {
+                /* Only little endian */
+                if (set[col]) {
+                    result[i++] = blue[col];
+                    result[i++] = green[col];
+                    result[i++] = red[col];
+                    result[i++] = alpha;
+                }
+                else {
+                    result[i++] = DEF_BLU;
+                    result[i++] = DEF_GRN;
+                    result[i++] = DEF_RED;
+                    result[i++] = alpha;
+                }
+            }
+        }
+    }
+    else {/* GREYSCALE IMAGE */
+        for (row = 0; row < rows; row++) {
+            Rast_get_row(map, (void *)voidc, row, rtype);
+            Rast_lookup_colors((void *)voidc, red, green, blue, set,
+                               cols, &colors, rtype);
+            
+            if(color_mode == 2) {
+                for (col = 0; col < cols; col++) {
+                    /*.33R+ .5G+ .17B */
+                    result[i++] = ((red[col])   * 11 + 
+                                   (green[col]) * 16 +
+                                   (blue[col])  * 5) >> 5;
+                }
+            } else {
+                for (col = 0; col < cols; col++) {
+                    /*NTSC Y equation: .30R+ .59G+ .11B */
+                    result[i++] = ((red[col])   * 19 + 
+                                   (green[col]) * 38 + 
+                                   (blue[col])  * 7) >> 6;
+                }
+            }
+        }
+    }
+
+    Rast_free_colors(&colors);
+
+    G_free(cell_buf);
+    G_free(fcell_buf);
+    G_free(dcell_buf);
+    G_free(red);
+    G_free(green);
+    G_free(blue);
+    G_free(set);
+    Rast_close(map);
+    
+    return(1);
+}