HueEffect.java

package com.sherazkhilji.videffects;

import android.opengl.GLSurfaceView;

import com.sherazkhilji.videffects.interfaces.ShaderInterface;


/**
 * Apply Hue effect on the video being played
 */
public class HueEffect implements ShaderInterface {

    private float hue;

    /**
     * Initialize Effect
     * <p>
     * <img alt="Hue value chart" width="400" height="350" src="https://cloud.githubusercontent.com/assets/2201511/21810115/b99ac22a-d74a-11e6-9f6c-ef74d15c88c7.jpg" >
     *
     * @param degrees Range of value should be between 0 to 360 degrees as described in the image above
     */
    public HueEffect(float degrees) {
        setDegrees(degrees);
    }

    public void setDegrees(float degrees) {
        hue = ((degrees - 45) / 45f + 0.5f) * -1;
    }

    @Override
    public String getShader(GLSurfaceView mGlSurfaceView) {
        return "#extension GL_OES_EGL_image_external : require\n"
                + "precision mediump float;\n"

                + "varying vec2 vTextureCoord;\n"
                + "uniform samplerExternalOES sTexture;\n"
                + "float hue=" + hue + ";\n"

                + "void main() {\n"

                + "vec4 kRGBToYPrime = vec4 (0.299, 0.587, 0.114, 0.0);\n"
                + "vec4 kRGBToI = vec4 (0.595716, -0.274453, -0.321263, 0.0);\n"
                + "vec4 kRGBToQ = vec4 (0.211456, -0.522591, 0.31135, 0.0);\n"

                + "vec4 kYIQToR = vec4 (1.0, 0.9563, 0.6210, 0.0);\n"
                + "vec4 kYIQToG = vec4 (1.0, -0.2721, -0.6474, 0.0);\n"
                + "vec4 kYIQToB = vec4 (1.0, -1.1070, 1.7046, 0.0);\n"


                + "vec4 color = texture2D(sTexture, vTextureCoord);\n"

                + "float YPrime = dot(color, kRGBToYPrime);\n"
                + "float I = dot(color, kRGBToI);\n"
                + "float Q = dot(color, kRGBToQ);\n"

                + "float chroma = sqrt (I * I + Q * Q);\n"

                + "Q = chroma * sin (hue);\n"

                + "I = chroma * cos (hue);\n"

                + "vec4 yIQ = vec4 (YPrime, I, Q, 0.0);\n"

                + "color.r = dot (yIQ, kYIQToR);\n"
                + "color.g = dot (yIQ, kYIQToG);\n"
                + "color.b = dot (yIQ, kYIQToB);\n"
                + "gl_FragColor = color;\n"

                + "}\n";
    }
}