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4fd2c2b3a3
Office scanners write the default decode array (/Decode [0 1 0 1 0 1]) on their page images. Reduce skipped every image with a decode array, so a scan stayed the same size. The default array is now treated as absent; any other array still skips the image. Reduce also saved its copy even when it wasn't smaller, reported as "-N% smaller". It now saves nothing and says the file is already as small as it can be made; doc_reduce returns "written": false. Optimize PDF still saves (what it discards may matter more than the size) but says "not smaller". Co-authored-by: Andrew Taylor <andrew.taylor@tayeng.com> Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com> Co-authored-by: Brandon Thomas <echelon@gmail.com>
pdfcraft-optimize
Layer L4: the PDF Optimizer (execution plan M11.1; Acrobat's Reduce File Size and Optimize PDF ▸ Advanced optimization).
let report = optimize(&mut doc, &Settings::default())?; // Reduce File Size's choices
// Or with progress: called before each image and the clean-up; `false` cancels.
let report = optimize_with_progress(&mut doc, &settings, &mut |stage| keep_going)?;
- Images: the effective resolution of each image is measured where pages draw it (the CTM through form XObjects; the smallest over all uses). Colour and grayscale images above a threshold are resampled with a bicubic (Catmull-Rom) filter to a target resolution and stored as JPEG (Acrobat's quality steps) or ZIP; soft masks are resampled with their image. An image is replaced only if the result is smaller. Left alone: CMYK and other colour spaces, image masks, decode arrays, more than 8 bits, JPEG 2000, JBIG2 and CCITT.
- Discard objects: thumbnails, alternate images, document tags, print settings.
- Clean up: Flate for streams with no filter.
The engine runs Remove Hidden Information (pdfcraft-redact) for the user-data categories,
then this, then merges identical objects and writes a full, compressed save
(pdfcraft_engine::optimizer::OptimizeJob, which the UI runs on a worker thread with a
progress bar). JPEG decoding and
encoding and resampling come from the image crate.