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

InvertFilterOpenGLView

@implementation InvertFilterOpenGLView

- (NSString *)getFragmetShaderString
{
    NSString *const kInvertFragmentShaderString = SHADER_STRING
    (
     varying highp vec2 textureCoordinate;

     uniform sampler2D inputImageTexture;

     void main()
     {
         lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);

         gl_FragColor = vec4((1.0 - textureColor.rgb), textureColor.w);
     }
     );

    return kInvertFragmentShaderString;
}

@end