Dramatically speed up ImageData:paste (issue #336)

src/modules/image/ImageData.cpp

@@ -24,22 +24,38 @@ namespace love
 {
 namespace image
 {
-	void ImageData::paste(ImageData * src, int dx, int dy, int sx, int sy, int sw, int sh)
-	{
-		pixel * s = (pixel *)src->getData();
-		pixel * d = (pixel *)getData();
+        void ImageData::paste(ImageData * src, int dx, int dy, int sx, int sy, int sw, int sh)
+        {
+                pixel * s = (pixel *)src->getData();
+                pixel * d = (pixel *)getData();
 
-		for (int i = 0; i < sh; i++)
-		{
-			for (int j = 0; j < sw; j++)
-			{
-				if (inside(dx+j, dy+i) && src->inside(sx+j, sy+i))
-				{
-					d[(dy+i)*getWidth() + (dx+j)] = s[(sy+i)*src->getWidth() + (sx+j)];
-				}
-			}
-		}
-	}
+                // Check bounds; if the data ends up completely out of bounds, get out early.
+                if (sx >= src->getWidth() || sx + sw < 0 || sy >= src->getHeight() || sy + sh < 0
+                 || dx >= getWidth() || dx + sw < 0 || dy >= getHeight() || dy + sh < 0)
+                        return;
+
+                // Normalize values to the inside of both images.
+                if (dx < 0) { sw += dx; sx -= dx; dx = 0; }
+                if (dy < 0) { sh += dy; sy -= dy; dy = 0; }
+                if (sx < 0) { sw += sx; dx -= sx; sx = 0; }
+                if (sy < 0) { sh += sy; dy -= sy; sy = 0; }
+                if (dx + sw > getWidth()) { sw = getWidth() - dx; }
+                if (dy + sh > getHeight()) { sh = getHeight() - dy; }
+                if (sx + sw > src->getWidth()) { sw = src->getWidth() - sx; }
+                if (sy + sh > src->getHeight()) { sh = src->getHeight() - sy; }
+
+                // If the dimensions match up, copy the entire memory stream in one go
+                if (sw == getWidth() && getWidth() == src->getWidth()
+                 && sh == getHeight() && getHeight() == src->getHeight())
+                        memcpy(d, s, sizeof(pixel) * sw * sh);
+                else    // Otherwise, copy each row individually
+                {
+                        for (int i = 0; i < sh; i++)
+                        {
+                                memcpy(d + dx + i * getWidth(), s + sx + i * src->getWidth(), sizeof(pixel) * sw);
+                        }
+                }
+        }
 
 	bool ImageData::inside(int x, int y) const
 	{