feat: Cache transparency property of image to improve thumbnail name prediction (#1365)

* Add transparency field to avoid accessing an image file to guess thumbnail names (esp. if using modern formats like webp)

* Add webp upload capability

* Default svg files to transparent

* Fix test migrations

* Remove unused import

Author: fsbraun

filer/migrations/0017_image__transparent.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.1.9 on 2023-06-21 16:57
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('filer', '0016_alter_folder_index_together_remove_folder_level_and_more'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='image',
+            name='_transparent',
+            field=models.BooleanField(default=False),
+        ),
+    ]

filer/models/abstract.py

@@ -1,5 +1,6 @@
 import logging
 
+import easy_thumbnails.utils
 from django.db import models
 from django.utils.functional import cached_property
 from django.utils.translation import gettext_lazy as _
@@ -39,6 +40,11 @@ class BaseImage(File):
         blank=True,
     )
 
+    _transparent = models.BooleanField(
+        null=False,
+        default=False,
+    )
+
     default_alt_text = models.CharField(
         _("default alt text"),
         max_length=255,
@@ -92,14 +98,18 @@ def file_data_changed(self, post_init=False):
                 imgfile.seek(0)
                 if self.mime_type == 'image/svg+xml':
                     self._width, self._height = VILImage.load(imgfile).size
+                    self._transparent = True
                 else:
-                    self._width, self._height = PILImage.open(imgfile).size
+                    pil_image = PILImage.open(imgfile)
+                    self._width, self._height = pil_image.size
+                    self._transparent = easy_thumbnails.utils.is_transparent(pil_image)
                 imgfile.seek(0)
             except Exception:
                 if post_init is False:
                     # in case `imgfile` could not be found, unset dimensions
                     # but only if not initialized by loading a fixture file
                     self._width, self._height = None, None
+                    self._transparent = False
         return attrs_updated
 
     def save(self, *args, **kwargs):

filer/templatetags/filer_admin_tags.py

@@ -9,7 +9,6 @@
 from django.utils.safestring import mark_safe
 from django.utils.translation import gettext_lazy as _
 
-from easy_thumbnails.conf import settings as thumbnail_settings
 from easy_thumbnails.files import get_thumbnailer
 from easy_thumbnails.options import ThumbnailOptions
 
@@ -127,10 +126,8 @@ def file_icon_context(file, detail, width, height):
             thumbnail_options = ThumbnailOptions(opts)
             # Optimize directory listing:
             if not detail and width == height and width in DEFERRED_THUMBNAIL_SIZES and hasattr(file, "thumbnail_name"):
-                # Avoid jpg thumbnails for pngs with transparency
-                transparent = file.file.name.rsplit(".", 1)[-1] == thumbnail_settings.THUMBNAIL_TRANSPARENCY_EXTENSION
                 # Get name of thumbnail from easy-thumbnail
-                configured_name = thumbnailer.get_thumbnail_name(thumbnail_options, transparent=transparent)
+                configured_name = thumbnailer.get_thumbnail_name(thumbnail_options, transparent=file._transparent)
                 # If the name was annotated: Thumbnail exists and we can use it
                 if configured_name == file.thumbnail_name:
                     icon_url = default_storage.url(configured_name)

tests/utils/extended_app/migrations/0001_initial.py

@@ -18,6 +18,7 @@ class Migration(migrations.Migration):
             fields=[
                 ('_height', models.FloatField(blank=True, null=True)),
                 ('_width', models.FloatField(blank=True, null=True)),
+                ('_transparent', models.BooleanField(null=False, default=False)),
                 ('default_alt_text', models.CharField(blank=True, max_length=255, null=True, verbose_name='default alt text')),
                 ('default_caption', models.CharField(blank=True, max_length=255, null=True, verbose_name='default caption')),
                 ('subject_location', models.CharField(blank=True, default='', max_length=64, verbose_name='subject location')),