Merge pull request #72 from patrickfournier/pillow-lazy-check

Wait before we actually need to process the image for checking if Pillow can handle it.

Author: patrickfournier

pelican/plugins/image_process/image_process.py

@@ -405,13 +405,6 @@ def compute_paths(img, settings, derivative):
 
 def process_img_tag(img, settings, derivative):
     path = compute_paths(img, settings, derivative)
-    if not is_img_identifiable(path.source):
-        logger.warning(
-            "%s Skipping image %s that could not be identified by Pillow",
-            LOG_PREFIX,
-            path.source,
-        )
-        return
     process = settings["IMAGE_PROCESS"][derivative]
 
     img["src"] = posixpath.join(path.base_url, path.filename)
@@ -423,23 +416,8 @@ def process_img_tag(img, settings, derivative):
     process_image((path.source, destination, process), settings)
 
 
-def is_img_identifiable(img_filepath):
-    try:
-        Image.open(img_filepath)
-        return True  # noqa: TRY300
-    except (FileNotFoundError, UnidentifiedImageError):
-        return False
-
-
 def build_srcset(img, settings, derivative):
     path = compute_paths(img, settings, derivative)
-    if not is_img_identifiable(path.source):
-        logger.warning(
-            "%s Skipping image %s that could not be identified by Pillow",
-            LOG_PREFIX,
-            path.source,
-        )
-        return
     process = settings["IMAGE_PROCESS"][derivative]
 
     default = process["default"]
@@ -685,17 +663,28 @@ def process_picture(soup, img, group, settings, derivative):
             img.insert_before(s["element"])
 
 
+def try_open_image(path):
+    try:
+        i = Image.open(path)
+    except UnidentifiedImageError:
+        logger.warning(
+            f'{LOG_PREFIX} Source image "{path}" is not supported by Pillow.'
+        )
+        raise
+    except FileNotFoundError:
+        logger.warning(f'{LOG_PREFIX} Source image "{path}" not found.')
+        raise
+
+    return i
+
+
 def process_image(image, settings):
     # remove URL encoding to get to physical filenames
     image = list(image)
     image[0] = unquote(image[0])
     image[1] = unquote(image[1])
     # image[2] is the transformation
 
-    logger.debug(f"{LOG_PREFIX} {image[0]} -> {image[1]}")
-
-    os.makedirs(os.path.dirname(image[1]), exist_ok=True)
-
     # If original image is older than existing derivative, skip
     # processing to save time, unless user explicitly forced
     # image generation.
@@ -704,7 +693,12 @@ def process_image(image, settings):
         or not os.path.exists(image[1])
         or os.path.getmtime(image[0]) > os.path.getmtime(image[1])
     ):
-        i = Image.open(image[0])
+        logger.debug(f"{LOG_PREFIX} Processing {image[0]} -> {image[1]}")
+
+        try:
+            i = try_open_image(image[0])
+        except (UnidentifiedImageError, FileNotFoundError):
+            return
 
         for step in image[2]:
             if callable(step):
@@ -713,12 +707,16 @@ def process_image(image, settings):
                 elems = step.split(" ")
                 i = basic_ops[elems[0]](i, *(elems[1:]))
 
+        os.makedirs(os.path.dirname(image[1]), exist_ok=True)
+
         # `save_all=True`  will allow saving multi-page (aka animated) GIF's
         # however, turning it on seems to break PNG support, and doesn't seem
         # to work on GIF's either...
         i.save(image[1], progressive=True)
 
         ExifTool.copy_tags(image[0], image[1])
+    else:
+        logger.debug(f"{LOG_PREFIX} Skipping {image[0]} -> {image[1]}")
 
 
 def dump_config(pelican):

pelican/plugins/image_process/test_image_process.py

@@ -5,16 +5,16 @@
 import subprocess
 import warnings
 
-from PIL import Image
+from PIL import Image, UnidentifiedImageError
 import pytest
 
 from pelican.plugins.image_process import (
     ExifTool,
     compute_paths,
     harvest_images_in_fragment,
-    is_img_identifiable,
     process_image,
     set_default_settings,
+    try_open_image,
 )
 
 # Prepare test image constants.
@@ -185,11 +185,6 @@ def test_image_formats(tmp_path, image_path):
     ],
 )
 def test_path_normalization(mocker, orig_src, orig_img, new_src, new_img):
-    # Allow non-existing images to be processed:
-    mocker.patch(
-        "pelican.plugins.image_process.image_process.is_img_identifiable",
-        lambda img_filepath: True,
-    )
     # Silence image transforms.
     process = mocker.patch("pelican.plugins.image_process.image_process.process_image")
 
@@ -505,11 +500,6 @@ def test_path_normalization(mocker, orig_src, orig_img, new_src, new_img):
     ],
 )
 def test_picture_generation(mocker, orig_tag, new_tag, call_args):
-    # Allow non-existing images to be processed:
-    mocker.patch(
-        "pelican.plugins.image_process.image_process.is_img_identifiable",
-        lambda img_filepath: True,
-    )
     process = mocker.patch("pelican.plugins.image_process.image_process.process_image")
 
     settings = get_settings(
@@ -626,19 +616,22 @@ def test_copy_exif_tags(tmp_path, image_path, copy_tags):
             assert tag not in actual_tags
 
 
-def test_is_img_identifiable():
+def test_try_open_image():
     for test_image in FILE_FORMAT_TEST_IMAGES:
-        assert is_img_identifiable(test_image)
+        assert try_open_image(test_image)
 
-    assert not is_img_identifiable("image/that/does/not/exist.png")
+    with pytest.raises(FileNotFoundError):
+        try_open_image("image/that/does/not/exist.png")
 
-    assert not is_img_identifiable(TEST_DATA.joinpath("folded_puzzle.png"))
-    assert not is_img_identifiable(TEST_DATA.joinpath("minimal.svg"))
+    with pytest.raises(UnidentifiedImageError):
+        assert not try_open_image(TEST_DATA.joinpath("folded_puzzle.png"))
+        assert not try_open_image(TEST_DATA.joinpath("minimal.svg"))
 
     img = {"src": "https://upload.wikimedia.org/wikipedia/commons/3/34/Exemple.png"}
     settings = get_settings(IMAGE_PROCESS_DIR="derivatives")
     path = compute_paths(img, settings, derivative="thumb")
-    assert not is_img_identifiable(path.source)
+    with pytest.raises(FileNotFoundError):
+        assert not try_open_image(path.source)
 
 
 def generate_test_images():