A tiled poster generator looks simple from the outside: load an image, choose a paper size, and download a PDF. The implementation becomes more interesting when the entire pipeline has to run in the browser, preserve physical dimensions, support overlapping pages, render a halftone effect, and avoid exhausting mobile memory.
I recently worked through those constraints while building Rasterbator.app. This article focuses on the engineering model behind the tool rather than the physical printing workflow.
The pipeline has five main stages:
Decode the source image locally.
Convert paper settings into one consistent coordinate system.
