Android OpenGL ES实现简单绿幕抠图

#extension GL_OES_EGL_image_external : require
precision mediump float;
                                
varying vec2 vTextureCoordinate;
uniform samplerExternalOES uTexture;

const float pixel = 30.0;
void main() {
    vec4 tc = texture2D(uTexture, vTextureCoordinate);
    float r = tc.x * 255.0;
    float g = tc.y * 255.0;
    float b = tc.z * 255.0;

    if(g>140.0 && r<128.0 && b<128.0){
        tc.x =1.0;
        tc.y =1.0;
        tc.z =1.0;
         tc.w =0.0;
    }else{
     tc.w =1.0;
    }

    gl_FragColor = tc, 1.0;
}

precision mediump float;

varying vec2 vTextureCoord;
varying vec2 vExtraTextureCoord;

uniform sampler2D uTexture;
uniform sampler2D uExtraTexture;

void main() {
    vec4 base = texture2D(uTexture, vTextureCoord);
    vec4 overlay = texture2D(uExtraTexture, vExtraTextureCoord);
    vec4 outputColor;
    if(base.r==1.0 && base.g==1.0 && base.b==1.0 && base.a==0.0){
      outputColor.r = base.a*base.r   overlay.r * (1.0 - base.a);
      outputColor.g = base.a*base.g   overlay.g * (1.0 - base.a);
      outputColor.b = base.a*base.b   overlay.b * (1.0 - base.a);
      outputColor.a = base.a;
    }else{
       outputColor.r = base.r;
       outputColor.g = base.g;
       outputColor.b = base.b;
       outputColor.a = base.a;
    }
    gl_FragColor = outputColor;
}