package com.marshalchen.common.uimodule.imageprocessing.filter.colour;
import android.opengl.GLES20;
import com.marshalchen.common.uimodule.imageprocessing.filter.BasicFilter;
/**
* A gamma adjustment filter extension of BasicFilter.
* This filter adjusts the gamma value of the input image.
* Values for gamma should be in [0, 3] for normal use; however, all values are excepted.
* This filter does not adjust alpha values.
* @author Chris Batt
*/
public class GammaFilter extends BasicFilter {
private static final String UNIFORM_GAMMA = "u_Gamma";
private float gamma;
private int gammaHandle;
/**
* Creates a ImageGammaFilter with the given gamma adjustment value.
* @param gamma
* The gamma adjustment value.
*/
public GammaFilter(float gamma) {
this.gamma = gamma;
}
@Override
protected String getFragmentShader() {
return
"precision mediump float;\n"
+"uniform sampler2D "+UNIFORM_TEXTURE0+";\n"
+"varying vec2 "+VARYING_TEXCOORD+";\n"
+"uniform float "+UNIFORM_GAMMA+";\n"
+"void main(){\n"
+" vec4 color = texture2D("+UNIFORM_TEXTURE0+","+VARYING_TEXCOORD+");\n"
+" gl_FragColor = vec4(pow(color.rgb, vec3("+UNIFORM_GAMMA+")), color.a);\n"
+"}\n";
}
@Override
protected void initShaderHandles() {
super.initShaderHandles();
gammaHandle = GLES20.glGetUniformLocation(programHandle, UNIFORM_GAMMA);
}
@Override
protected void passShaderValues() {
super.passShaderValues();
GLES20.glUniform1f(gammaHandle, gamma);
}
}