sketch:MultipassFilter< { darkness:{ default:1.5; description:"How dark the lines get; higher looks more like heavy pencil."; label:"Darkness"; max:4; min:0.5; step:0.01; type:"float"; }; sigma:{ default:3; description:"Thickness of the lines in pixels."; label:"Line width σ (px)"; max:20; min:0.5; step:0.1; type:"float"; unit:"px"; }; }, > = ...
Pencil sketch: colour dodge of the luminance by its blurred copy, min(1, L / blur(L))^darkness on
sRGB-encoded luminance (the classic "invert, blur, colour-dodge", since 1 − blur(1 − L) = blur(L)).
Flat areas become white paper, the dark side of every edge a grey line whose width follows σ.
Transparent pixels count as paper; alpha is kept.
Pencil sketch: colour dodge of the luminance by its blurred copy, min(1, L / blur(L))^darkness on sRGB-encoded luminance (the classic "invert, blur, colour-dodge", since 1 − blur(1 − L) = blur(L)). Flat areas become white paper, the dark side of every edge a grey line whose width follows σ. Transparent pixels count as paper; alpha is kept.