What survives screenshots and recompression?

Method and actual sample

Eight separate photographs by Thomas Bresson, licensed CC BY 2.0, were selected from Wikimedia Commons. They are a convenience sample from one photographer: 8 photographs, 0 generated images. The longer-term target of 20 mixed-source originals has not been reached.

We alphabetized the first ten results of a Commons file search for “filetype:bitmap Thomas Bresson” and excluded two originals larger than 10 MiB before extracting fields. Source descriptions and camera categories document the photographic context; metadata alone cannot authenticate the scene.

1. Keep the downloaded original unchanged and record its SHA-256 hash.
2. Apply EXIF orientation to pixels, convert to RGB, resize the longest side to at most 1536 with LANCZOS, then export JPEG with Pillow 12.3.0 at quality 85 and subsampling 2. Do not pass metadata to the encoder.
3. Display the original inside an 800 × 600 white viewport with contain sizing. Capture PNG at device scale 1 using Chromium 152.0.7977.54. This is a local browser screenshot.

Pillow independently read field presence, including the EXIF sub-IFD. Separately, the site’s header reader inspected its normal first 64 KiB. We recorded absence and errors rather than filling missing fields. There were 0 reference parse errors.

A repeat run using an isolated Python environment with the same pinned Pillow version reproduced all 24 field-presence and product-signal observations and the aggregate counts. All eight original hashes matched. One screenshot PNG differed in bytes between runs without changing its observed fields; browser captures are not promised to be byte-identical. Original files, source evidence and run records are retained outside the source repository. Public sources below allow a reader to retrieve and hash-check the same originals.