Added CustomBlend example

java/examples/Topics/Shaders/CustomBlend/data/difference.glsl

@@ -0,0 +1,22 @@
+uniform sampler2D destSampler;
+uniform sampler2D srcSampler;
+
+uniform ivec2 destSize;
+uniform ivec4 destRect;
+
+uniform ivec2 srcSize;
+uniform ivec4 srcRect;
+
+varying vec4 vertTexCoord;
+
+void main() {
+  vec2 st = vertTexCoord.st;   
+  
+  vec2 dest = vec2(destRect.xy) / vec2(destSize) + st * vec2(destRect.zw) / vec2(destSize);
+  vec2 src = vec2(srcRect.xy) / vec2(srcSize) + st * vec2(srcRect.zw) / vec2(srcSize); 
+  
+  vec3 destColor = texture2D(destSampler, dest).rgb;
+  vec3 srcColor = texture2D(srcSampler, src).rgb;
+  
+  gl_FragColor = vec4(abs(srcColor - destColor), 1.0);  
+}