2 effects

Edge Detection & Outlines

Edge detection asks a narrow question of every pixel: how different is it from its neighbors? Where the answer is large you are on a boundary - the edge of a face, a horizon, the join between two colors - and drawing only those answers turns a photograph into a line drawing. Edge Outline does that, with control over how sensitive the detection is, how thick the line comes out, and whether you keep the image underneath or throw it away.

Impossible Shadows uses the same structural reading for the opposite purpose. Instead of drawing the boundaries it treats the image's brightness as height and casts shadows across it, from directions that need not agree with each other - which is why the shadows read as wrong in a way a real light could not produce.

This is the smallest category, and both effects are at their best as a layer rather than an ending. Put an outline on its own layer above the picture, set that layer's blend mode, and you get an ink pass over an untouched photograph; mask it, and you get one only where you want it. An outline stacked over pixel sorting also gives the smear back an edge to sit against.