# CZOA HEIC decoder source and relinking kit

This kit corresponds to the separately loaded library module
`/vendor/heic/libheif-d1a93baf2da8.mjs`, SHA-256
`d1a93baf2da80de406a5355c8620037358aaf8465e3b1f54185eaa05f6d37797`.
It contains unmodified libheif 1.22.2 and libde265 1.0.16 source archives,
the actual linked library object archives, the original libheif post.js,
exported ABI, explicit build options, and original license/copyright files.
Only the libde265 HEVC decoder is enabled. Examples, other codec plugins,
plugin loading and multithreaded decoding are disabled.

The LGPL-covered library portions may be modified, replaced and reverse
engineered for debugging those modifications under the included licenses.
Nothing in this documentation or the site's terms limits those rights.
CZOA does not claim ownership of the included libraries. The adapter sources
in `adapter/` document the application/library interface; they are separate
from the library module and contain no user photographs or credentials.

## Reproduce the original link

Use Emscripten 4.0.15 (recorded compiler revision in build-plan.json), with
its environment configured as documented by the Emscripten project. The
original build used CMake 3.31.8 and a single compilation job. Toolchain
archive URLs, checksums and the embedded WASM memory limit are recorded in
source.json alongside this downloadable kit. No package installation is
performed by these scripts.

Run:

```sh
python3 relink.py --emcc /path/to/emscripten/emcc --output replacement-libheif.mjs
```

The command uses the supplied objects and exact original link options.
`--libheif`, `--libde265` and `--post-js` accept replacement object archives
or modified libheif post.js. The module has a default factory export and
uses embedded WASM; no separate WASM download is required.

## Rebuild library source

```sh
python3 rebuild.py --emscripten /path/to/emscripten --cmake /path/to/cmake --work ./rebuilt
```

This extracts the included source archives to `rebuilt/sources/`, compiles
one job at a time, and relinks `rebuilt/libheif.mjs`. To modify a library,
edit the extracted source and rerun: existing source directories are kept.
Emscripten's system-library cache is placed in the work directory unless
`EM_CACHE` is already set. Original source archive hashes are listed in
SHA256SUMS.json; modified source naturally changes those hashes.

## Use a replacement module

The application loads this library as a separate same-origin ES module.
In a local copy or installation you control, replace the module at the
above URL, or change `decoderUrl` in the supplied `heic.worker.ts` adapter
to the replacement module's URL. The filename's hash text is a cache key;
the application does not enforce it as an integrity restriction. Retain
the default factory and HeifDecoder/HeifImage API expected by the adapter.
The included adapters show the size checks and worker message protocol.
Run a local HTTP server supporting ES modules; a file:// URL is not an
appropriate browser module environment. This does not grant access to
modify another person's server or any production account.

The library module's maximum WASM linear memory is 512 MiB. The CZOA
adapter independently limits each source to 75 MiB and 48,000,000 pixels
before RGBA allocation; the browser worker is terminated after each job.
The bound applies to WASM linear memory, not the browser's entire memory.
Photograph pixel correctness, browser support and site release acceptance
are separate from the source/relinking evidence.

Full source and original notices for the Emscripten runtime are supplied in
`emscripten-runtime-source.tar.gz` alongside this kit, with the exact
compiler/toolchain references in source.json. Applicable licenses are in
`licenses/` and NOTICE.txt alongside the kit. The source archives preserve
original per-file copyright and license headers.