Candidate routes
Authored teaching scenario. Every observation, prediction and record below was written for this exercise. None was produced by running image software or by examining an image, and nothing here supports a claim about how any real tool or forensic technique behaves.

Two processing histories someone has proposed for Output 7.
What each one predicts is in observations.csv, beside what was observed.
Your job is to apply the tolerance and say whether the observations can
tell the two routes apart.

Route A -- resize once, save once
  1. Open the 2400 x 1600 source
  2. Resize to 1200 x 800
  3. Save as JPEG at quality 78

Route B -- save, resize, save again
  1. Open the 2400 x 1600 source
  2. Save as JPEG at quality 90
  3. Reopen that saved file and resize to 1200 x 800
  4. Save as JPEG at quality 78

Source: image/source -- an authored image, 2400 x 1600
Artefact: image/output-7 -- provenance unknown -- this is the question