YcRcBA Compositing with GLSL

fragshader.fsh

varying highp vec2 v_texCoord;												

uniform sampler2D u_YTex;
uniform sampler2D u_cRTex;
uniform sampler2D u_cBTex;
uniform sampler2D u_ATex;

void main()																
{		
    
    const lowp mat3 M = mat3 (1.164,   1.164, 1.164,
                                0.0, -0.3917, 2.01723,
                              1.5960, -0.812, 0.0);
    const lowp vec3 postBias = vec3(-0.870, 0.529,  -1.0813);
    
    lowp vec4 p;
    lowp float Y = texture2D(u_YTex, v_texCoord.st).x;
    lowp float cB = texture2D(u_cBTex, v_texCoord.st).x;
    lowp float cR = texture2D(u_cRTex, v_texCoord.st).x;
    lowp float A = texture2D(u_ATex, v_texCoord.st).x;
    p.a = A;
    p.xyz = M * vec3(Y,cB,cR) + postBias;
    gl_FragColor = p;
}