Pixel Diff vs Structural Diff for PDFs — Two Very Different Problems

All tests run on an 8-year-old MacBook Air. "Compare these two PDFs" sounds like one problem. It's actually two completely different problems depending on what you mean. Hiyoko PDF Vault implements both. Here's the difference. Pixel diff: what changed visually Render both PDFs to images, compare pixel by pixel. Highlights visual differences — layout shifts, image changes, text that moved. pub fn pixel_diff ( page_a : & [ u8 ], // rendered PNG bytes page_b : & [ u8 ], ) -> DiffResult { le