Lab

Poster Composer

Lab
Overprint in the browser: three ink plates, basic shapes and freehand, mirrored on the centre axis.
Year
2026
Tools
  • JavaScript
  • Canvas
  • SVG
  • Multiply

Open tool Runs right in the browser, nothing to install.

The idea

In screen printing and risograph, colour comes from separate plates that mix in overprint. Can this logic be rebuilt so that you see the print while you draw?

What it’s for

Poster and cover drafts with a real print feel in minutes. Formats from A4 to story, and the plates can later be separated directly for printing.

Three spot colours sit on separate layers and are combined in multiply mode: where red and blue meet, dark blue appears as in overprint. You draw with rectangle, ellipse, triangle or freely with the pen.

  • Seven formats from A4 portrait to story 9:16
  • Mirroring on the centre axis, grid and snapping to the middle
  • Stroke weight from filled area to outline, fine grain as on a risograph
  • Select shapes, move them or put them on another plate, undo and redo
  • Eight ink sets based on real riso inks, paper colour of your choice, a generator for compositions
  • Export as PNG at 300 dpi, as SVG and as one separation per plate for printing