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<languageVersion : 1.0;>

kernel Exclusion

<   namespace : "Flame";

    vendor : "Adobe";

    version : 1;

    description : "Exclusion blend mode";

>

{

    input image4 dst;

    input image4 src;

    output pixel4 result;



    void

    evaluatePixel()

    {

        pixel4 a = sampleNearest(dst,outCoord()); // cb

        pixel4 b = sampleNearest(src,outCoord()); // cs

        

        // remove premultiplied (srcCP/srcA, dstCP/dstA)

        //pixel3 cb, cs;

        pixel3 cb = a.rgb;

        pixel3 cs = b.rgb;



        if (a.a > 0.0) {

            cb.rgb = a.rgb / a.a;

        }

        if (b.a > 0.0) {

            cs.rgb = b.rgb / b.a;

        }

        

        // dstA' = (1-srcA)*dstA + srcA

        result.a = (1.0-b.a)*a.a + b.a;

        

        // temp for Blend(srcCP/srcA, dstCP/dstA)

        float3 blendResult;

        

        // cb + cs � 2*cs*cb

        blendResult.rgb = cb.rgb + cs.rgb - 2.0*cs.rgb*cb.rgb;

        

        // dstCP' = (1-srcA)*dstCP + (1-dstA)*srcCP + srcA*dstA*Blend(srcCP/srcA, dstCP/dstA)

        result.rgb = ((1.0-b.a)*a.rgb) + ((1.0-a.a)*b.rgb) + b.a*a.a*blendResult.rgb;

    }

}