//Simply apply a filter to an UIImage.
- (void)viewDidLoad
{
    UIImage* srcImage = [UIImage imageNamed:@"test.jpg"];
    //HSL Adjust (hue: 0.02, saturation: -0.31, luminance: -0.17)
    //Please see the manual for more details.
    const char* ruleString = @"@adjust hsl 0.02 -0.31 -0.17";
    UIImage* resultImage = cgeFilterUIImage_MultipleEffects(srcImage, ruleString, 1.0f, nil);

    //Then the dstImage is applied with the filter.
    //It's so convenient, isn't it?
}

// A simple customized filter to do a color reversal.
class MyCustomFilter : public CGE::CGEImageFilterInterface
{
public:
    
    bool init()
    {
        CGEConstString fragmentShaderString = CGE_SHADER_STRING_PRECISION_H
        (
        varying vec2 textureCoordinate;  //defined in 'g_vshDefaultWithoutTexCoord'
        uniform sampler2D inputImageTexture; // the same to above.

        void main()
        {
            vec4 src = texture2D(inputImageTexture, textureCoordinate);
            src.rgb = 1.0 - src.rgb;  //Simply reverse all channels.
            gl_FragColor = src;
        }
        );

        //m_program is defined in 'CGEImageFilterInterface'
        return m_program.initWithShaderStrings(g_vshDefaultWithoutTexCoord, s_fsh);
    }

    //void render2Texture(CGE::CGEImageHandlerInterface* handler, GLuint srcTexture, GLuint vertexBufferID)
    //{
    //  //Your own render functions here.
    //  //Do not override this function to use the CGEImageFilterInterface's.
    //}
};