Gamedev Lounge 0010

[Mag]

OK, didn't exactly understand what you meant by indexing image before. So you want to add an extra texture to avoid loops?

There would be no way to determine if the current color is closest to the palette color except by checking every color in the palette. This shader isn't just useful for alternative palettes, but for forcing a base image to only consist of colors in your palette.

Using a texture only for positioning would still require a check to make sure the color is the exact same and you would lose that closest color functionality, which adds just too many features at a low performance cost. That's not to say it's not impossible or impractical, just not as useful.

Code:

/**
* returns color in palette closest to inputed color.
*/
vec4 colorPalette(vec4 inColor, sampler2D texPalette) {
    vec4 outColor = vec4(0.0);
    float minDis = 4.0;
    float dis = 3.0;

    if (inColor.a > 0.001) {
        for (int i = 0; i < SAMPLES; i++) {
            vec4 palleteColor = texture2D(texPalette, vec2((float(i) + 0.5) / float(SAMPLES), 0.5));
            dis = sqrDistance(rgbToHsl(inColor).rgb, rgbToHsl(palleteColor).rgb);
            if (palleteColor.a > 0.001) {
                if (dis < minDis) {
                    minDis = dis;
                    outColor = palleteColor;
                }
            }
        }
    }
    return outColor;
}

I did do some changes to my code now on the question of performance and making it more elegant. The starting distance and minimum distance variables have been changed to their highest possible values in the script (sqrDistance of a vec3 color is going to be 3, as pure white is 1 + 1 + 1.). Also changed some of the starting var constructors to their smaller forms.