Is JPEG or PNG Better for Images Inside a PDF?
Direct answer
JPEG is usually smaller for photographs and continuous-tone scans because it is lossy. PNG-style lossless encoding is often better for flat graphics, transparency, screenshots, and sharp-edged diagrams, but can be much larger for photographs.
Why this happens
Format choice should follow image content rather than the PDF filename. Photographic noise creates many color variations that lossless compression must preserve, while JPEG can discard subtle detail efficiently.
Logos, line art, and screenshots can develop halos or blur around hard edges when encoded as JPEG. Transparency also needs special handling because JPEG has no alpha channel.
A PDF may contain several image encodings at once. Re-encoding every image to one format can reduce size but may be the wrong choice for some graphics.
Choose by image type
- Photographs and full-page color scans: JPEG is often practical.
- Logos, diagrams, screenshots, and transparency: retain lossless data when needed.
- Black-and-white document scans may benefit from specialized monochrome encodings.
- Inspect edges, small labels, and transparency after conversion.
What BytesPDF does
BytesPDF's current compression pipeline re-encodes supported image streams as JPEG and paints onto a white background. Keep the original when transparency or lossless line-art fidelity is required.
Do not use aggressive JPEG recompression for barcodes, compliance marks, or diagnostic imagery without testing.
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