Added interface to raster only one shape

src/nanosvgrast.h

@@ -65,6 +65,11 @@ void nsvgRasterize(NSVGrasterizer* r,
 				   NSVGimage* image, float tx, float ty, float scale,
 				   unsigned char* dst, int w, int h, int stride);
 
+// Use shapeFilter to only rasterize a single shape. NULL to disable
+void nsvgRasterizeEx(NSVGrasterizer* r,
+					 NSVGimage* image, NSVGshape* shapeFilter, float tx, float ty, float scale,
+					 unsigned char* dst, int w, int h, int stride);
+
 // Deletes rasterizer context.
 void nsvgDeleteRasterizer(NSVGrasterizer*);
 
@@ -1365,9 +1370,9 @@ static void dumpEdges(NSVGrasterizer* r, const char* name)
 }
 */
 
-void nsvgRasterize(NSVGrasterizer* r,
-				   NSVGimage* image, float tx, float ty, float scale,
-				   unsigned char* dst, int w, int h, int stride)
+void nsvgRasterizeEx(NSVGrasterizer* r,
+					 NSVGimage* image, NSVGshape* shapeFilter, float tx, float ty, float scale,
+					 unsigned char* dst, int w, int h, int stride)
 {
 	NSVGshape *shape = NULL;
 	NSVGedge *e = NULL;
@@ -1392,6 +1397,9 @@ void nsvgRasterize(NSVGrasterizer* r,
 		if (!(shape->flags & NSVG_FLAGS_VISIBLE))
 			continue;
 
+		if (shapeFilter && shape != shapeFilter)
+			continue;
+
 		if (shape->fill.type != NSVG_PAINT_NONE) {
 			nsvg__resetPool(r);
 			r->freelist = NULL;
@@ -1454,6 +1462,14 @@ void nsvgRasterize(NSVGrasterizer* r,
 	r->stride = 0;
 }
 
+void nsvgRasterize(NSVGrasterizer* r,
+					 NSVGimage* image, float tx, float ty, float scale,
+					 unsigned char* dst, int w, int h, int stride)
+{
+	nsvgRasterizeEx(r, image, NULL,  tx,  ty,  scale,
+					dst, w, h, stride);
+}
+
 #endif // NANOSVGRAST_IMPLEMENTATION
 
 #endif // NANOSVGRAST_H