Add svg2png image conversion function

Author: benoit74

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Add utility function to compute ZIM Tags #164, including deduplication #156
+- Add svg2png image conversion function #113
 
 ## Changed
 - **BREAKING** Renamed `zimscraperlib.image.convertion` to `zimscraperlib.image.conversion` to fix typo

pyproject.toml

@@ -22,6 +22,7 @@ dependencies = [
   # promise is that they will never (or always) break the API, and the API is very
   # limited and we use only a very small subset of it.
   "regex>=2020.7.14",
+  "CairoSVG>=2.2.0,<3.0",
   # youtube-dl should be updated as frequently as possible
   "yt-dlp"
 ]

src/zimscraperlib/image/conversion.py

@@ -3,9 +3,11 @@
 
 from __future__ import annotations
 
+import io
 import pathlib
 from typing import IO
 
+import cairosvg.svg
 from PIL.Image import open as pilopen
 
 from zimscraperlib.constants import ALPHA_NOT_SUPPORTED
@@ -40,6 +42,39 @@ def convert_image(
         save_image(image, dst, fmt, **params)
 
 
+def convert_svg2png(
+    src: str | pathlib.Path | io.BytesIO,
+    dst: pathlib.Path | IO[bytes],
+    width: int | None = None,
+    height: int | None = None,
+):
+    """Convert a SVG to a PNG
+
+    Output width and height might be specified if resize is needed.
+    PNG background is transparent.
+    """
+    kwargs = {}
+    if isinstance(src, pathlib.Path):
+        src = str(src)
+    if isinstance(src, str):
+        kwargs["url"] = src
+    else:
+        kwargs["bytestring"] = src.getvalue()
+    if width:
+        kwargs["output_width"] = width
+    if height:
+        kwargs["output_height"] = height
+    if isinstance(dst, pathlib.Path):
+        cairosvg.svg2png(write_to=str(dst), **kwargs)
+    else:
+        result = cairosvg.svg2png(**kwargs)
+        if not isinstance(result, bytes):
+            raise Exception(
+                "Unexpected type returned by cairosvg.svg2png"
+            )  # pragma: no cover
+        dst.write(result)
+
+
 def create_favicon(src: pathlib.Path, dst: pathlib.Path) -> None:
     """generate a squared favicon from a source image"""
     if dst.suffix != ".ico":

tests/image/test_image.py

@@ -17,7 +17,11 @@
 from resizeimage.imageexceptions import ImageSizeError
 
 from zimscraperlib.image import presets
-from zimscraperlib.image.conversion import convert_image, create_favicon
+from zimscraperlib.image.conversion import (
+    convert_image,
+    convert_svg2png,
+    create_favicon,
+)
 from zimscraperlib.image.optimization import (
     ensure_matches,
     get_optimization_method,
@@ -328,6 +332,42 @@ def test_convert_path_src_io_dst(png_image: pathlib.Path):
     assert dst_image.format == "PNG"
 
 
+def test_convert_svg_io_src_path_dst(svg_image: pathlib.Path, tmp_path: pathlib.Path):
+    src = io.BytesIO(svg_image.read_bytes())
+    dst = tmp_path / "test.png"
+    convert_svg2png(src, dst)
+    dst_image = Image.open(dst)
+    assert dst_image.format == "PNG"
+
+
+def test_convert_svg_io_src_io_dst(svg_image: pathlib.Path):
+    src = io.BytesIO(svg_image.read_bytes())
+    dst = io.BytesIO()
+    convert_svg2png(src, dst)
+    dst_image = Image.open(dst)
+    assert dst_image.format == "PNG"
+
+
+def test_convert_svg_path_src_path_dst(svg_image: pathlib.Path, tmp_path: pathlib.Path):
+    src = svg_image
+    dst = tmp_path / "test.png"
+    convert_svg2png(src, dst, width=96, height=96)
+    dst_image = Image.open(dst)
+    assert dst_image.format == "PNG"
+    assert dst_image.width == 96
+    assert dst_image.height == 96
+
+
+def test_convert_svg_path_src_io_dst(svg_image: pathlib.Path):
+    src = svg_image
+    dst = io.BytesIO()
+    convert_svg2png(src, dst, width=96, height=96)
+    dst_image = Image.open(dst)
+    assert dst_image.format == "PNG"
+    assert dst_image.width == 96
+    assert dst_image.height == 96
+
+
 @pytest.mark.parametrize(
     "fmt,exp_size",
     [("png", 128), ("jpg", 128)],