MaskFilter.java

package com.marshalchen.common.uimodule.imageprocessing.filter.blend;

import com.marshalchen.common.uimodule.imageprocessing.filter.MultiInputFilter;

/**
 * Applies a mask blend of two images.  The luminance of the second image determines the alpha of the first.
 * @author Chris Batt
 */
public class MaskFilter extends MultiInputFilter {
	public MaskFilter() {
		super(2);
	}
	
	@Override
	protected String getFragmentShader() {
		return 
				 "precision mediump float;\n" 
				+"uniform sampler2D "+UNIFORM_TEXTURE0+";\n"  
				+"uniform sampler2D "+UNIFORM_TEXTUREBASE+1+";\n" 
				+"varying vec2 "+VARYING_TEXCOORD+";\n"	
				
		  		+"void main(){\n"
		  		+"   vec4 color1 = texture2D("+UNIFORM_TEXTURE0+","+VARYING_TEXCOORD+");\n"
		  		+"   vec4 color2 = texture2D("+UNIFORM_TEXTUREBASE+1+","+VARYING_TEXCOORD+");\n"
		  		+"   float newAlpha = dot(color2.rgb, vec3(.33333334, .33333334, .33333334)) * color2.a;\n"
		  		+"   gl_FragColor = vec4(color1.xyz, newAlpha);\n"
		  		+"}\n";	
	}
}