Fast RGBA to HSVA in Unity3D shader

RGBA2HSVA

//Original source
//http://lolengine.net/blog/2013/01/13/fast-rgb-to-hsv
//http://ploobs.com.br/?p=1499

#ifndef RGBA2HSVA
#define RGBA2HSVA
fixed4 RGBA2HSVA(fixed4 rgba)
{
    float K = 0;
    fixed temp;

    if (rgba.g < rgba.b)
    {
        temp = rgba.b;
        rgba.b = rgba.a;
        rgba.a = temp;
        
        K = -1;
    }

    if (r < g)
    {
        temp = rgba.r;
        rgba.r = rgba.g;
        rgba.g = temp;
        K = -2 / 6 - K;
    }

    fixed chroma = r - min(g, b);
    h = abs(K + (g - b) / (6 * chroma + 1e-20));
    s = chroma / (r + 1e-20);
    v = r;
    return float4(h,s,v,rgba.a);
}

fixed3 Hue(fixed H)
{
    fixed R = abs(H * 6 - 3) - 1;
    fixed G = 2 - abs(H * 6 - 2);
    fixed B = 2 - abs(H * 6 - 4);
    return saturate(fixed3(R,G,B));
}

fixed4 HSVtoRGB(fixed4 HSV)
{
    return fixed4(((Hue(HSV.x) - 1) * HSV.y + 1) * HSV.z,HSV.w);
}

#endif