Firefox Extension Exports PDFs Using Only Browser APIs, No External Library

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A developer building Longshot, a Firefox screenshot extension, created a 336-line PDF exporter without relying on any external PDF library. The approach works because two key tasks a PDF library would normally handle — JPEG encoding and zlib compression — are already natively supported by the browser through canvas.toBlob and CompressionStream respectively. These browser APIs align directly with PDF's built-in /DCTDecode and /FlateDecode stream filters, allowing image data to pass through without re-encoding. The developer notes this is a narrow solution covering only image placement and invisible text layers, not the full range of features a general PDF library provides. A key engineering decision was to assemble the file as raw bytes with precisely measured offsets, since a single incorrect entry in PDF's cross-reference table renders the entire file unreadable without any obvious error.

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ProgrammingDEV Community ·

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