Replace optipng with pyoxipng

Avoid spawning a subprocess and installing an OS package.

Author: twm

.github/workflows/ci.yml

@@ -59,7 +59,7 @@ jobs:
     - name: apt install
       run: |
         sudo apt-get update
-        sudo apt-get install --no-install-suggests --no-install-recommends inkscape icoutils scour optipng
+        sudo apt-get install --no-install-suggests --no-install-recommends inkscape icoutils scour
 
     - uses: actions/[email protected]
       with:

README.md

@@ -24,7 +24,7 @@ The [conventions document](./conventions.md) describes some idioms used in the c
 
 Grab the build dependencies with:
 
-    $ sudo apt install brotli inkscape icoutils git scour optipng \
+    $ sudo apt install brotli inkscape icoutils git scour \
                        python3-dev build-essential
 
 [Install pip](https://pip.pypa.io/en/latest/installing/#get-pip), then install [Tox](http://tox.readthedocs.org/en/latest/).

bin/compile-static.py

@@ -1,5 +1,5 @@
 #!/usr/bin/python3
-# Copyright © 2018, 2019, 2020, 2022, 2024 Tom Most <[email protected]>
+# Copyright © 2018, 2019, 2020, 2022, 2024, 2025 Tom Most <[email protected]>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -55,6 +55,7 @@
 from typing import Optional, Sequence
 
 import brotli
+import oxipng
 import tinycss2
 import zopfli.gzip
 
@@ -220,7 +221,7 @@ async def rasterize_favicon(favicon: Path, build_dir: Path, w: Writer) -> None:
     """
     Use Inkscape to generate two raster versions of the favicon:
 
-    - icon-[hexchars].png — a 152x152 PNG, optimized with optipng.
+    - icon-[hexchars].png — a 152x152 PNG, optimized with oxipng.
     - icon-[hexchars].ico — ICO with 16x16, 24x24, 32x32, and 64x64 versions.
       Built with icotool.
     """
@@ -240,13 +241,19 @@ async def rasterize_favicon(favicon: Path, build_dir: Path, w: Writer) -> None:
             raise ProcFailed(f"inkscape failed to write {outfile!r}", stdout, stderr)
 
     png_path = Path(outfiles.pop())
-    ico_path = build_dir / f"{favicon.stem}.ico"
-    await asyncio.gather(
-        _run(["optipng", "-quiet", str(png_path)]),
-        _run(["icotool", "--create", "-o", str(ico_path), *outfiles]),
+    oxipng.optimize(
+        str(png_path),
+        level=4,
+        interlace=oxipng.Interlacing.Off,
+        strip=oxipng.StripChunks.safe(),
+        deflate=oxipng.Deflaters.zopfli(15),
+        optimize_alpha=True,
     )
-
     w.add_file(hashname("icon", "png", png_path.read_bytes()), png_path)
+
+    ico_path = build_dir / f"{favicon.stem}.ico"
+    # icotool reencodes the PNGs with libpng, so there's no point optimizing them.
+    await _run(["icotool", "--create", "-o", str(ico_path), *outfiles])
     w.add_file(hashname("icon", "ico", ico_path.read_bytes()), ico_path)
 
 

requirements_static.in

@@ -1,3 +1,4 @@
 brotli
 tinycss2
 zopfli
+pyoxipng

requirements_static.txt

@@ -6,6 +6,8 @@
 #
 brotli==1.1.0
     # via -r requirements_static.in
+pyoxipng==9.1.0
+    # via -r requirements_static.in
 tinycss2==1.4.0
     # via -r requirements_static.in
 webencodings==0.5.1