Contrast

Stretch or flatten every color channel about mid grey.

Each channel moves away from the middle of the encoded range by factor, so 2f doubles the distance from mid grey and 0.5f halves it. The pivot is the encoded signal's midpoint, which is what filter: contrast() in a browser pivots on, and a channel that stretches past black or white clamps there.

On an export that keeps an HDR grade the pivot is the light that midpoint makes on an SDR display at reference white, about 44 cd/m2, and a channel stretches up to the format's peak rather than to white.

Throws