1 files changed, 27 insertions, 0 deletions
diff --git a/wimmel.frag b/wimmel.frag
new file mode 100644
index 0000000..d4cb7ef
--- /dev/null
+++ b/wimmel.frag
@@ -0,0 +1,27 @@
+varying vec2 v_texcoord;
+uniform sampler2D tex;
+uniform vec2 pixelsize;
+uniform vec4 search_rect;
+uniform int barrier;
+
+void
+main()
+{
+	float i, j;
+	float width = search_rect[2];
+	float height = search_rect[3];
+	int diff = 0;
+
+	for (i = 0.0; i < width && diff < barrier; i += pixelsize.x) {
+		for (j = 0.0; j < height && diff < barrier; j += pixelsize.y) {
+			vec4 match = texture2D(tex, search_rect.xy + vec2(i,j));
+			vec4 orig = texture2D(tex, v_texcoord + vec2(i,j));
+
+			diff += int(any(greaterThan(abs(orig - match), vec4(0.2))));
+		}
+	}
+
+	gl_FragColor = vec4(float(diff < barrier), 0.0, 0.0, 0.0);
+}
+
+// vim:ft=c: