Drop lightness weight toward 0 to key on hue alone — that kills shadows and gradients on an otherwise even backdrop.
Decontaminate un-mixes the backdrop colour out of semi-transparent edge pixels. Push it up if you see a coloured fringe.
Matte is computed on a working copy then resampled to full resolution on export, so output keeps the source pixels.
Keyboard Shortcuts:
Engine Architecture:
Every operation here is closed-form arithmetic: sRGB→CIELAB conversion, nearest-neighbour ΔE against sampled key colours, a smoothstep falloff, scanline flood fill, separable min/max morphology, box-blur feather, and Vlahos-style unpremultiply for decontamination. No model weights, zero tracking, nothing leaves your tab.