The conference needed my slides as images for a legacy uploader that rejected PDFs. Six pages, ten minutes, no admin rights to install anything. Each page rendered at double scale, downloaded as JPGs, zipped, uploaded — done before coffee cooled. PDF-to-image is a rendering job: scale sets sharpness, quality sets weight, and the two multiply. This guide covers the 1×/2× decision, JPEG-vs-PNG exports, batch memory discipline and ZIP delivery.
Part of the PDF workflow guide. Render in PDF to JPG; bundle outputs with the ZIP Creator approach below. Text instead? See text extraction.
1× vs 2×: 96 DPI previews vs 192 DPI print
| Scale | Effective DPI | 6-page ZIP | Use for |
|---|---|---|---|
| 1× | ~96 | Small | Web previews, chat, tickets |
| 2× | ~192 | Medium | Print, slides, archives |
| 2× PNG | ~192 | Large | Diagrams, sharp text |
My 6-page brochure: 1× JPEG landed a featherweight ZIP, 2× JPEG stayed crisp at full-page print, 2× PNG ballooned (correctly — diagrams demand it). Rule: match scale to the viewing medium, not your ambition. Test one page first; the first render predicts the batch.
JPEG 85% vs PNG: photos compress, diagrams don't
JPEG at 85% quality is the photo default — smooth gradients, small files, invisible loss. PNG preserves razor text and flat colors at 3–5× the bytes. So: brochure portraits → JPG; architecture diagrams → PNG; mixed decks → JPG unless a page is diagram-heavy (then PNG that page). Below 70% JPEG quality, gradient banding appears — hold 85% as the floor for anything public. Transparency flattens to white on export; check thumbnails for black-background surprises from dark-mode sources.
Batch memory: 50 pages per pass on phones
Each rendered page is a full bitmap in RAM: 200 pages at 2× can stall phones and even breathed-hard laptops. Discipline: under 50 pages per batch on mobile, close redundant tabs, prefer 1× on old devices, and download the ZIP between batches (don't accumulate hundreds of object URLs). Very large PDFs split first at range extraction — two 100-page passes beat one crashed 200-page attempt. Filenames arrive as page-01.jpg sequences; rename the ZIP (brochure-images.zip) before distributing.
General guidance only. Rendering is pixel-exact at the chosen scale — zoom the first output before batching the rest.