Re: Compositing math in SVG

I am optimizing the blend modes and over. I got stuck with color dodge.

This is the general compositing formula from SVG spec, for
over and some blend mode B:

result = alpha_a * (1-alpha_b) * Cs + alpha_a * alpha_b * B(Cb,Cs) +
alpha_b * (1-alpha_a) * Cb

and the code for color dodge is:

float colordodge (float Cb, float Cs) {
    if (b == 1) return 1;
    return min (1.0f, Cb/(1-Cs));
}

I am not sure if I can ignore the clamping part and just use Cb/(1-Cs) for
B(Cb,Cs) in the
general compositing formula, and then simplify it. And, only then clamp.

Are there completely reduced versions of the combinations of blend modes
with over somewhere?

Thanks