bias gain inflection point

biasgaininf.c

float evalCurve(float x, float tx, float ty, float sa, float sb)
{
    const float EPS = 1e-6f;
    if (x < tx) {
        return (ty * x) / (x + sa * (tx - x) + EPS);
    } else {
        return ((1-ty) * (x-1)) / ((1-x) - sb * (tx - x) + EPS) + 1.0f;
    }
}

float tx = pts[0].x; // Inflection point
float ty = pts[0].y;
float slope = (pts[0].y - pts[1].y) / (pts[0].x - pts[1].x); // Second control point controls slope
float slopea = slope * ((tx-0)/(ty-0));
float slopeb = slope * ((1-tx)/(1-ty));
float y = evalCurve(x, tx, ty, slopea, slopeb);