Why PDF compression quietly turns your text into a picture

说明与用途

PDF压缩时常会导致文本丢失，使用 PDFLib 对未过滤流进行 deflate 可在保持所有字符的同时减小文件大小。

问题

Compressing a text PDF often results in a rasterized image, losing selectable text.

结果

The lossless repack reduced file size by 3.4× compared to the best raster result while keeping all text selectable.

工作流

• Load source PDF
• Copy pages into a fresh document
• Save with useObjectStreams:true
• Identify raw streams without /Filter
• Deflate those streams with FlateDecode
• Replace original streams with compressed ones
• Preserve original if deflate not beneficial
• Re‑save document

证据

A 6-page text PDF went from 298.7 KB to 8.9 KB with every one of its 26,652 characters still selectable.

来源

Lossless came out 3.4× smaller than the best raster result, and it was the only row where the text survived at all.

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Walk every indirect object in the document. For each raw stream whose dictionary has no /Filter, deflate it and label it…

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