Example : Color Space Processing

In this example, we will write a script to process an image in the HSV space, and transform it back to RGB. We will be using the color primitives script and the inclusion mechanism.

// The output format will be identical as the input format :
REQUIRED_FORMAT:outputFormat(inputFormat)
CALL:FORMAT_TO_CONSTANT(outputFormat)

// Load the color primitives (this file is distributed with the project) :
INCLUDE(colors.ppl)

// Change the colors in the HSV space :
SOURCE:ChangeHSVShader
{
        #version 130
        uniform sampler2D textureInput;
        out vec4 textureChangedHSV;
        
        // Get the color primitives from the loaded file :
        #pragma INSERT(ColorPrimitives)
        #pragma INSERT(outputFormat)

        // The parameters to be changed dynamically :
        uniform float   vScaling = 1.0,
                        sScaling = 1.0, 
                        hRotate = 0.0;

        void main()
        {
                // Get the input data :
                vec2 pos = gl_FragCoord.xy/vec2(outputFormat);
                vec3 rgb = textureLod(textureInput, pos, 0.0).rgb,
                     hsv;
                
                // To HSV
                RGBToHSV(rgb, hsv);

                // Modifications : 
                hsv.z = hsv.z * vScaling;
                hsv.y = hsv.y * sScaling;
                hsv.x = mod(hsv.x + hRotate * 360.0, 360);

                // Back to RGB
                HSVToRGB(hsv, rgb);

                // Write the output data :
                textureChangedHSV.rgb = rgb;
        }
}

FILTER_LAYOUT:ChangeHSVFilter(outputFormat, ChangeHSVShader)

PIPELINE_MAIN:ChangeHSVPipeline
{
        INPUT_PORTS(textureInput)
        OUTPUT_PORTS(textureChangedHSV)
        FILTER_INSTANCE:ChangeHSVFilter
}

We can also predefined values to the the uniform variables (see Glip::Modules::UniformsVarsLoader) :

PIPELINE:changeHSVPipeline
{
        FILTER:changeHSVFilter
        {
                GL_FLOAT:vScaling(1.1)
                GL_FLOAT:sScaling(1.2)
                GL_FLOAT:hRotate(0.01)
        }
}

Splitted output example (original is on top-left corner) :