This is Filter for https://github.com/kazukitanaka0611/GLCameraTemplate

２値化

#pragma mark -
- (NSString *)getFragmentShaderString
{
  NSString *const kFragmentShaderString = SHADER_STRING
  (
    varying highp vec2 textureCoordinate;

    uniform sampler2D inputImageTexture;
 
 
     const highp vec3 W = vec3(0.2125, 0.7154, 0.0721);
 
     void main()
     {
　　　　// To gray
         highp float gray = step(0.5,dot(texture2D(inputImageTexture, textureCoordinate).rgb, W));
 
         lowp vec4 colorToDisplay = vec4(1.0, 1.0, 1.0, 1.0);

         if (gray < 1.00)
         {
            colorToDisplay = vec4(1.0, 0.0, 0.0, 1.0);
         }
         
         gl_FragColor = colorToDisplay;
     }
     );
 
    return kFragmentShaderString;
}