package com.marshalchen.common.uimodule.imageprocessing.filter.colour;
import com.marshalchen.common.uimodule.imageprocessing.filter.BasicFilter;
/**
* A grey scale filter extension of the BasicFilter.
* The grey scale filter is implemented by setting red, green and blue to the average of red, green and blue.
* The alpha value of the input is preserved.
* @author Chris Batt
*/
public class GreyScaleFilter extends BasicFilter {
@Override
protected String getFragmentShader() {
return
"precision mediump float;\n"
+"uniform sampler2D "+UNIFORM_TEXTURE0+";\n"
+"varying vec2 "+VARYING_TEXCOORD+";\n"
+"vec3 W = vec3(0.2125, 0.7154, 0.0721);\n"
+"void main(){\n"
+" vec4 color = texture2D("+UNIFORM_TEXTURE0+","+VARYING_TEXCOORD+");\n"
+" float grey = dot(color.rgb, W);\n"
+" gl_FragColor = vec4(grey, grey, grey, color.a);"
+"}\n";
}
}