Added basic skin detector filter

src/core/canvas.js

@@ -178,6 +178,7 @@ exports.canvas = function() {
     canvas.vignette = wrap(vignette);
     canvas.vibrance = wrap(vibrance);
     canvas.sepia = wrap(sepia);
+    canvas.skin = wrap(skin);
 
     return canvas;
 };

src/filters/adjust/skin.js

@@ -0,0 +1,34 @@
+/**
+ * @filter         Skin
+ * @description    Filters-out pixels not matching skin color.
+ * from: 
+ * Human skin color clustering for face detection
+ * J. Kovac, P. Peer, F. Solina - 2003
+ */
+function skin() {
+    gl.skin = gl.skin || new Shader(null, '\
+        uniform sampler2D texture;\
+        varying vec2 texCoord;\
+        void main() {\
+            vec4 color = texture2D(texture, texCoord);\
+            float r = color.r;\
+            float g = color.g;\
+            float b = color.b;\
+            \
+            if ((r>45.0/255.0)&&(g>40.0/255.0)&&(b>20.0/255.0)\
+                &&(r>g)&&(r>b)\
+                &&(r-min(g,b)>15.0/255.0)\
+                &&(abs(r-g)>15.0/255.0)){\
+                gl_FragColor = color;\
+            } else {\
+                gl_FragColor = vec4(0.0,0.0,0.0,color.a);\
+            }\
+        }\
+    ');
+
+    simpleShader.call(this, gl.skin, {
+        amount: clamp(0, 1)
+    });
+
+    return this;
+}