check for and remove transparency before saving files in non-transparent-capable formats

sqlalchemy_media/processors.py

@@ -394,8 +394,13 @@ def process(self, descriptor: StreamDescriptor, context: dict):
         # Cropping
         if self.crop:
             img = img.crop(self.crop)
-
-        img.save(output_buffer, format=format_)
+        try:
+            img.save(output_buffer, format=format_)
+        except (OSError):
+            if img.mode in ("RGBA", "P"):
+                img = img.convert("RGB")
+            img.save(output_buffer, format=format_)
+
         self._update_context(img, format_, context)
         output_buffer.seek(0)
         descriptor.replace(output_buffer, position=0, **context)

sqlalchemy_media/tests/test_image_processors.py

@@ -14,6 +14,7 @@ def setUpClass(cls):
         cls.stuff_path = join(cls.this_dir, 'stuff')
         cls.cat_jpeg = join(cls.stuff_path, 'cat.jpg')
         cls.cat_png = join(cls.stuff_path, 'cat.png')
+        cls.cat_png_alpha = join(cls.stuff_path, 'rgba-cat.png')
         cls.dog_jpg = join(cls.stuff_path, 'dog_213X160.jpg')
 
     def test_resize_reformat(self):
@@ -32,6 +33,20 @@ def test_resize_reformat(self):
                 'height': 150,
                 'extension': '.jpg'
             })
+
+        with AttachableDescriptor(self.cat_png_alpha) as d:
+            ctx = dict(
+                length=100000,
+                extension='.jpg',
+            )
+            ImageProcessor(fmt='jpeg', width=200).process(d, ctx)
+
+            self.assertDictEqual(ctx, {
+                'content_type': 'image/jpeg',
+                'width': 200,
+                'height': 150,
+                'extension': '.jpg'
+            })
 
         with AttachableDescriptor(self.cat_jpeg) as d:
             # Checking when not modifying stream.