Add utility to fetch and prepare ZIM illustration

Author: benoit74

CHANGELOG.md

@@ -16,6 +16,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - JS rewriting abusively rewrite import function (#255)
 
+### Added
+
+- Add utility to fetch and prepare ZIM illustration (#254)
+
 ## [5.1.1] - 2025-02-17
 
 ### Changed

src/zimscraperlib/constants.py

@@ -29,3 +29,6 @@
 # default timeout to get responses from upstream when doing web requests ; this is not
 # the total time it gets to download the whole resource
 DEFAULT_WEB_REQUESTS_TIMEOUT = 10
+
+DEFAULT_ZIM_ILLLUSTRATION_SIZE = 48
+DEFAULT_ZIM_ILLLUSTRATION_SCALE = 1

src/zimscraperlib/image/illustration.py

@@ -0,0 +1,52 @@
+import io
+import pathlib
+
+from zimscraperlib.constants import DEFAULT_ZIM_ILLLUSTRATION_SIZE
+from zimscraperlib.image.conversion import convert_image, convert_svg2png
+from zimscraperlib.image.optimization import optimize_png
+from zimscraperlib.image.probing import format_for
+from zimscraperlib.image.transformation import resize_image
+from zimscraperlib.inputs import handle_user_provided_file
+
+
+def get_zim_illustration(
+    illustration_location: pathlib.Path | str,
+    width: int = DEFAULT_ZIM_ILLLUSTRATION_SIZE,
+    height: int = DEFAULT_ZIM_ILLLUSTRATION_SIZE,
+    resize_method: str = "contain",
+) -> io.BytesIO:
+    """Get ZIM-ready illustration from any image path or URL
+
+    illustration_location will be downloaded if needed. Image is automatically
+    converted to PNG, resized and optimized as needed.
+
+    Arguments:
+        illustration_location: path or URL to an image
+        width: target illustration width
+        height: target illustration height
+        resize_method: method to resize the image ; in general only 'contain' or
+          'cover' make sense, but 'crop', 'width', 'height' and 'thumbnail' can be used
+    """
+
+    illustration_path = handle_user_provided_file(illustration_location)
+
+    if not illustration_path:
+        # given handle_user_provided_file logic, this is not supposed to happen besides
+        # when empty string is passed, hence the simple error message
+        raise ValueError("Illustration is missing")
+
+    illustration = io.BytesIO()
+    illustration_format = format_for(illustration_path, from_suffix=False)
+    if illustration_format == "SVG":
+        convert_svg2png(illustration_path, illustration, width, height)
+    else:
+        if illustration_format != "PNG":
+            convert_image(illustration_path, illustration, fmt="PNG")
+        else:
+            illustration = io.BytesIO(illustration_path.read_bytes())
+        resize_image(illustration, width, height, method=resize_method)
+
+    optimized_illustration = io.BytesIO()
+    optimize_png(illustration, optimized_illustration)
+
+    return optimized_illustration

src/zimscraperlib/zim/metadata.py

@@ -10,6 +10,8 @@
 import regex
 
 from zimscraperlib.constants import (
+    DEFAULT_ZIM_ILLLUSTRATION_SCALE,
+    DEFAULT_ZIM_ILLLUSTRATION_SIZE,
     ILLUSTRATIONS_METADATA_RE,
     MAXIMUM_DESCRIPTION_METADATA_LENGTH,
     MAXIMUM_LONG_DESCRIPTION_METADATA_LENGTH,
@@ -423,8 +425,8 @@ def __init__(
 @mandatory
 class DefaultIllustrationMetadata(IllustrationBasedMetadata):
     meta_name = "Illustration_48x48@1"
-    illustration_size: int = 48
-    illustration_scale: int = 1
+    illustration_size: int = DEFAULT_ZIM_ILLLUSTRATION_SIZE
+    illustration_scale: int = DEFAULT_ZIM_ILLLUSTRATION_SCALE
 
 
 @mandatory

tests/image/test_illustration.py

@@ -0,0 +1,69 @@
+from pathlib import Path
+
+import pytest
+from PIL.Image import open as pilopen
+
+from zimscraperlib.image.illustration import get_zim_illustration
+
+COMMONS_IMAGE_PATH = (Path(__file__) / "../../files/commons.png").resolve()
+COMMONS_48_IMAGE_PATH = (Path(__file__) / "../../files/commons48.png").resolve()
+NINJA_IMAGE_PATH = (Path(__file__) / "../../files/ninja.webp").resolve()
+
+
+@pytest.mark.parametrize(
+    "user_illustration, expected_max_filesize",
+    [
+        pytest.param(COMMONS_IMAGE_PATH, 5000, id="big_commons"),
+        pytest.param(COMMONS_48_IMAGE_PATH, 4000, id="small_commons"),
+        pytest.param(NINJA_IMAGE_PATH, 5000, id="ninja"),
+        pytest.param(
+            "https://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Commons-logo.svg/250px-Commons-logo.svg.png",
+            4000,
+            id="png_url",
+        ),
+        pytest.param(
+            "https://upload.wikimedia.org/wikipedia/commons/4/4a/Commons-logo.svg",
+            4000,
+            id="svg_url",
+        ),
+    ],
+)
+def test_get_zim_illustration(
+    user_illustration: str | Path,
+    expected_max_filesize: int,
+):
+    image = get_zim_illustration(user_illustration)
+    assert len(image.getvalue()) < expected_max_filesize
+    with pilopen(image) as image_details:
+        assert image_details.format == "PNG"
+        assert image_details.size == (48, 48)
+
+
+def test_get_missing_user_zim_illustration():
+    with pytest.raises(Exception, match="missing.png could not be found"):
+        get_zim_illustration("./missing.png")
+
+
+def test_get_missing_default_zim_illustration():
+    with pytest.raises(Exception, match="Illustration is missing"):
+        get_zim_illustration("")
+
+
+def test_get_zim_illustration_custom_size():
+    image = get_zim_illustration(NINJA_IMAGE_PATH, 96, 120)
+    assert len(image.getvalue()) < 21000
+    with pilopen(image) as image_details:
+        assert image_details.format == "PNG"
+        assert image_details.size == (96, 120)
+
+
+def test_get_zim_illustration_method():
+    image_cover = get_zim_illustration(NINJA_IMAGE_PATH, resize_method="cover")
+    image_contain = get_zim_illustration(NINJA_IMAGE_PATH, resize_method="contain")
+    # cover image is always bigger than contain image size more pixels are
+    # "used/non-transparent"
+    assert len(image_cover.getvalue()) > len(image_contain.getvalue())
+    for image in [image_cover, image_contain]:
+        with pilopen(image) as image_details:
+            assert image_details.format == "PNG"
+            assert image_details.size == (48, 48)