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7/23/2026
Building a Browser-Based Tiled Poster PDF Generator

Building a Browser-Based Tiled Poster PDF Generator

Short summary

Engineering deep-dive into building Rasterbator.app, a fully browser-based tiled poster PDF generator that runs without a server. Covers coordinate system unification (mm/inches to PDF points), deterministic page grid calculation with overlap handling, and memory-efficient halftone preview rendering via Canvas pixel sampling. Emphasizes local-only image processing for privacy and mobile memory constraints.

  • •Five-stage pipeline: decode, coordinate conversion, grid calculation, preview/halftone, PDF render — all client-side
  • •Handles paper margins, overlap regions, and aspect-ratio-preserving page grid with centering offsets
  • •Uses Canvas downsampling for efficient halftone previews instead of full-resolution rendering

Generated with AI, which can make mistakes.

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