JPG or PNG for PDF pages? We measured the file sizes
When you save PDF pages as images you choose between PNG and JPG. The usual advice is that PNG is for text and JPG is for photos. We measured it with the PDF to image tools on ReshapePDF to see how much it matters.
How we measured
We converted three one-page PDFs with the PDF to PNG and PDF to JPG tools. Pages are rendered at twice the PDF's point size (about 144 dpi) and JPG is saved at 92% quality. The pages were: a letter of Romanian text, a report page with text, a table and a blue block, and a page holding a 512 × 512 pixel photo (a public-domain NASA photograph that ships as a sample image with the scikit-image library).
| Page | PNG | JPG | Smaller |
|---|---|---|---|
| Text letter (1190 × 1683 px) | 159 KB | 197 KB | PNG, 19% smaller |
| Report page (1224 × 1584 px) | 140 KB | 157 KB | PNG, 11% smaller |
| Photo page (1024 × 1024 px) | 535 KB | 169 KB | JPG, about 3 times smaller |
What the numbers say
On pages made of text and flat colour, PNG was 11 to 19% smaller than a high-quality JPG, and it has no compression artefacts around letters. On the photo page, JPG was about three times smaller. JPG is good at smooth gradients and noise, which is what a photograph is made of.
What to pick
- Text, forms and screenshots of documents: PNG.
- Pages dominated by photos: JPG.
- You need a very small file from a text page: neither. Send the PDF itself, or extract only the pages you need.
Caveats
Three pages are a small sample. The JPG quality in the tool is fixed at 92%, so a lower setting would give smaller JPG files that we did not measure. Scanned pages are photographs of paper and may behave more like the photo page than like the text pages.