wcap: Compute per-component deltas

src/screenshooter.c

@@ -240,6 +240,18 @@ output_run(uint32_t *p, uint32_t delta, int run)
 	return p;
 }
 
+static uint32_t
+component_delta(uint32_t next, uint32_t prev)
+{
+	unsigned char dr, dg, db;
+
+	dr = (next >> 16) - (prev >> 16);
+	dg = (next >>  8) - (prev >>  8);
+	db = (next >>  0) - (prev >>  0);
+
+	return (dr << 16) | (dg << 8) | (db << 0);
+}
+
 static void
 weston_recorder_frame_notify(struct wl_listener *listener, void *data)
 {
@@ -295,7 +307,7 @@ weston_recorder_frame_notify(struct wl_listener *listener, void *data)
 				stride * (r[i].y2 - j - 1) + r[i].x1;
 			for (k = 0; k < width; k++) {
 				next = *s++;
-				delta = (next - *d) & 0x00ffffff;
+				delta = component_delta(next, *d);
 				*d++ = next;
 				if (run == 0 || delta == prev) {
 					run++;

wcap/wcap-decode.c

@@ -42,6 +42,7 @@ wcap_decoder_decode_rectangle(struct wcap_decoder *decoder,
 	uint32_t v, *p = decoder->p, *d;
 	int width = rect->x2 - rect->x1, height = rect->y2 - rect->y1;
 	int x, i, j, k, l, count = width * height;
+	unsigned char r, g, b, dr, dg, db;
 
 	d = decoder->frame + (rect->y2 - 1) * decoder->width;
 	x = rect->x1;
@@ -55,8 +56,14 @@ wcap_decoder_decode_rectangle(struct wcap_decoder *decoder,
 			j = 1 << (l - 0xe0 + 7);
 		}
 
+		dr = (v >> 16);
+		dg = (v >>  8);
+		db = (v >>  0);
 		for (k = 0; k < j; k++) {
-			d[x] = (d[x] + v) | 0xff000000;
+			r = (d[x] >> 16) + dr;
+			g = (d[x] >>  8) + dg;
+			b = (d[x] >>  0) + db;
+			d[x] = 0xff000000 | (r << 16) | (g << 8) | b;
 			x++;
 			if (x == rect->x2) {
 				x = rect->x1;