filter for brightness and contrast

brightnesscontrast.pbk

<languageVersion : 1.0;>

kernel BrightContrast
<   namespace : "jp.ncsoft.image.filters";
    vendor : "maroo";
    version : 1;
    description : "adjust contrast and brightness";
>

{
    input image4 src;
    output pixel4 dst;
    
    // Set up sliders
     parameter float contrast
    <
        defaultValue :1.0;
        minValue : 0.0;
        maxValue : 10.0;
    >;
    
     parameter float brightness
    <
        defaultValue :1.0;
        minValue : 0.0;
        maxValue : 10.0;
    >;

    void
    evaluatePixel()
    {
        dst = sampleNearest(src,outCoord());
        // Contrast Filter. 
        /*All colour values are between 0.0 and 1.0
        / By subtracting 0.5 we make 0 the treshold. 
        / All values under 0 get smaller as contrast increases
        / and all values over get bigger, i.e. more contrast!
        */
        dst.r = ((dst.r - 0.5)*contrast)+ 0.5;
        dst.g = ((dst.g - 0.5)*contrast)+ 0.5;
        dst.b = ((dst.b - 0.5)*contrast)+ 0.5;
        //Brightness Filter
        /* Simply multiply by a number more then 1 to increase
        / and a number less than 1 to decrease.
        */
        dst.r = dst.r * brightness;
        dst.g = dst.g * brightness;
        dst.b = dst.b * brightness;
        
    }
}