ColourDodgeBlendFilter.java

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

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

/**
 * Applies a color dodge blend of two images
 * @author Chris Batt
 */
public class ColourDodgeBlendFilter extends MultiInputFilter {
	public ColourDodgeBlendFilter() {
		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"
		  		+"   vec3 baseOverlayAlphaProduct = vec3(color2.a * color1.a);\n"
		  		+"   vec3 rightHandProduct = color2.rgb * (1.0 - color1.a) + color1.rgb * (1.0 - color2.a);\n"
		  		+"   vec3 firstBlendColor = baseOverlayAlphaProduct + rightHandProduct;\n"
		  		+"   vec3 overlayRGB = clamp((color2.rgb / clamp(color2.a, 0.01, 1.0)) * step(0.0, color2.a), 0.0, 0.99);\n"
		  		+"   vec3 secondBlendColor = (color1.rgb * color2.a) / (1.0 - overlayRGB) + rightHandProduct;\n"
		  		+"   vec3 colorChoice = step((color2.rgb * color1.a + color1.rgb * color2.a), baseOverlayAlphaProduct);\n"
	   			+"   gl_FragColor = vec4(mix(firstBlendColor, secondBlendColor, colorChoice), 1.0);\n"
		  		+"}\n";	
	}
}