The previous patch_jpegdec.py used in-place string replacement with a
single shared marker for two distinct DC writes (main store and
successive-approximation update). If only one of the two anchors
matched, the file was written half-patched and the shared marker locked
the partial state in for every subsequent run.
Generate the fixes as `git format-patch` artifacts under
scripts/jpegdec_patches/, then apply them in lexical order via
`git apply`. Idempotency is decided by git itself: `--check --reverse`
succeeds means already applied; `--check` succeeds means appliable;
neither aborts the build rather than leaving a half-patched file.
No behaviour change to the patched JPEGDEC source: same redirect, same
DC guards, same intent. Just stops the pre-build script from doing
something it has no business doing.
EIGHT_BIT_GRAYSCALE decode of a 3-component progressive JPEG calls
JPEGDecodeMCU_P with MCU_SKIP for Cb and Cr after every Y MCU. The
existing safe-pMCU patch redirects the wild pointer to &sMCUs[0] but
leaves the DC store unguarded, so each chroma skip overwrites the
just-decoded Y DC with the chroma DC predictor. Output reads sMCUs[0],
gets the trailing Cr DC (~0), and renders an all-black image.
Add `if (iMCU >= 0)` guards to the two pMCU[0] writes (main DC store
and successive-approximation update). The pointer redirect stays as the
AC wild-pointer defence; the new guards stop the silent corruption at
sMCUs[0]. The two fixes are independent and both required.
- GHA release workflow is updated to use an action for uploading all assets. The
action docs say it updates a release if one already exists, and since this
triggers on release and we pass a release tag we know the release already
exists.
- GHA release candidate workflow is updated to auto-publish a pre-release
release on push to a `release/**` branch. A script is added and used to
generate a release message made up of the commits since the last release of
any kind.
- ACT profiles are added to allow locally testing these workflows without
needing to push and wait for GHA to run.
- Docs are updated to note how to test the workflows locally.
## Summary
The progressive JPEG fixes (AC table skip, MCU_SKIP guard) from PR #1136
have been fixed upstream in bitbank2/JPEGDEC@8628297. Pin to that commit
and remove the pre-build patch script.
## Additional Context
Tested on Strange Pictures epub
---
### AI Usage
While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.
Did you use AI tools to help write this code? _**< PARTIALLY >**_
Jeremy Klein