r.grow: shrink for negative radius

git-svn-id: https://svn.osgeo.org/grass/grass/branches/releasebranch_7_0@59736 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.grow/main.c

@@ -24,6 +24,9 @@
 #include <grass/raster.h>
 #include <grass/glocale.h>
 
+#ifdef MAX
+#undef MAX
+#endif
 #define MAX(a, b)	((a) > (b) ? (a) : (b))
 
 static int size;
@@ -115,6 +118,7 @@ int main(int argc, char **argv)
     DCELL *out_row;
     int nrows, row;
     int ncols, col;
+    int shrink;
 
     G_gisinit(argv[0]);
 
@@ -163,7 +167,13 @@ int main(int argc, char **argv)
     in_name = opt.in->answer;
     out_name = opt.out->answer;
 
+    shrink = 0;
+
     radius = atof(opt.rad->answer);
+    if (radius < 0) {
+	shrink = 1;
+	radius = -radius;
+    }
 
     if (opt.old->answer)
 	oldval = atoi(opt.old->answer);
@@ -227,38 +237,66 @@ int main(int argc, char **argv)
 	for (col = 0; col < ncols; col++) {
 	    DCELL *c = &in_rows[size][col];
 
-	    if (!Rast_is_d_null_value(c)) {
-		if (opt.old->answer) {
-		    if (oldval < 0)
+	    if (shrink) {
+		if (Rast_is_d_null_value(c)) {
+		    Rast_set_d_null_value(&out_row[col], 1);
+		    continue;
+		}
+
+		for (i = 0; i < count; i++) {
+		    int dx = neighbors[i][0];
+		    int dy = neighbors[i][1];
+		    int x = col + dx;
+		    int y = row + dy;
+
+		    if (x < 0 || x >= ncols || y < 0 || y >= nrows)
+			continue;
+
+		    c = &in_rows[size + dy][x];
+
+		    if (Rast_is_d_null_value(c)) {
 			Rast_set_d_null_value(&out_row[col], 1);
-		    else
-			out_row[col] = oldval;
+			break;
+		    }
 		}
-		else
-		    out_row[col] = *c;
 
-		continue;
+		if (i == count)
+		    out_row[col] = *c;
 	    }
+	    else {
+		if (!Rast_is_d_null_value(c)) {
+		    if (opt.old->answer) {
+			if (oldval < 0)
+			    Rast_set_d_null_value(&out_row[col], 1);
+			else
+			    out_row[col] = oldval;
+		    }
+		    else
+			out_row[col] = *c;
 
-	    for (i = 0; i < count; i++) {
-		int dx = neighbors[i][0];
-		int dy = neighbors[i][1];
-		int x = col + dx;
-		int y = row + dy;
-
-		if (x < 0 || x >= ncols || y < 0 || y >= nrows)
 		    continue;
+		}
 
-		c = &in_rows[size + dy][x];
+		for (i = 0; i < count; i++) {
+		    int dx = neighbors[i][0];
+		    int dy = neighbors[i][1];
+		    int x = col + dx;
+		    int y = row + dy;
 
-		if (!Rast_is_d_null_value(c)) {
-		    out_row[col] = opt.new->answer ? newval : *c;
-		    break;
+		    if (x < 0 || x >= ncols || y < 0 || y >= nrows)
+			continue;
+
+		    c = &in_rows[size + dy][x];
+
+		    if (!Rast_is_d_null_value(c)) {
+			out_row[col] = opt.new->answer ? newval : *c;
+			break;
+		    }
 		}
-	    }
 
-	    if (i == count)
-		Rast_set_d_null_value(&out_row[col], 1);
+		if (i == count)
+		    Rast_set_d_null_value(&out_row[col], 1);
+	    }
 	}
 
 	Rast_put_d_row(out_fd, out_row);

raster/r.grow/r.grow.html

@@ -7,6 +7,8 @@ more than one cell (by varying the size of the <b>radius</b>
 parameter), or like <em>r.buffer</em>, but with the
 option of preserving the original cells (similar to combining
 <em>r.buffer</em> and <em>r.patch</em>).
+<p>
+A negative <b>radius</b> shrinks inwards instead of growing outwards.
 
 
 <h2>NOTES</h2>
@@ -56,18 +58,13 @@ candidates with the same northing, the westernmost is chosen.
 
 <h2>EXAMPLE</h2>
 
-You can shrink inwards by preparing an inverse map first, and then
-inverting the resulting grown map. For example:
+You can shrink inwards by using a negative radius. For example:
 <div class="code"><pre>
-# Spearfish sample dataset
-
-MAP=fields
-g.region rast=$MAP
-r.mapcalc "inverse = if(isnull($MAP), 1, null())"
-r.grow in=inverse out=inverse.grown
-r.mapcalc "$MAP.shrunken = if(isnull(inverse.grown), $MAP, null())"
-r.colors $MAP.shrunken rast=$MAP
-g.remove inverse,inverse.grown
+# North Carolina sample dataset
+
+g.region rast=lakes
+r.grow in=lakes out=lakes.shrunken radius=-2.01
+r.colors lakes.shrunken rast=lakes
 </pre></div>