Lossless PDF stream compression (Flate / Deflate).
Lossless compression reduces file size by reorganizing structural metadata, stripping duplicate font subsets, and applying Flate/Deflate zlib encoding to raw content streams.
Because lossless compression is 100% reversible, 0% visual quality is lost. However, lossless compression alone usually achieves only 10% to 25% size reduction if the PDF contains heavy scanned images.
Lossy image stream optimization (DCT & Downsampling).
To achieve 70% to 90% size reductions (e.g. shrinking a 3 MB document under 200 KB), lossy image compression is required for embedded photo and scan streams.
Zcompressor intelligently separates vector text elements (which remain 100% lossless) from background raster graphics (which undergo smart bicubic resampling and JPEG DCT quantization).
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Frequently Asked Questions.
Does Zcompressor use lossy or lossless compression?
Zcompressor uses a hybrid model: 100% lossless compression for vector text, fonts, and layout structures, combined with smart lossy downsampling for heavy embedded images.