Platecaster is for risograph printmakers preparing small-edition poster separations. Each source image has to become a set of registration-safe spot-colour plates before ink reaches paper, with enough visibility to catch weak thresholds, muddy overlaps, and insufficient trapping.
The usual workaround is to posterize and threshold an image in Photoshop, duplicate channels into plate layers, then toggle those layers while manually compensating for registration drift. A new illustration, paper stock, or ink combination means repeating the separation and checking the geometry again.
Platecaster quantizes luminance into three named ink plates, applies adjustable ordered dithering and registration trap expansion, and provides composite or individual plate inspection. The interface quantifies the pixel mutations caused by threshold and trap controls. Its preview and downloaded layered SVG come from the same separation state.
Project marker: platecaster-2026-08-12.
The release verifier runs the deployed workflow against the canonical portrait fixture, writes fresh layered SVG bytes, and reruns the committed validator. Shipment requires the live tool to produce the three promised spot-colour groups and registration marks, rather than merely drawing a convincing preview.