Don't let _resize_and_fill/_resize_and_crop scale a side down to zero

src/diffusers/image_processor.py

@@ -400,8 +400,11 @@ def _resize_and_fill(
         ratio = width / height
         src_ratio = image.width / image.height
 
-        src_w = width if ratio < src_ratio else image.width * height // image.height
-        src_h = height if ratio >= src_ratio else image.height * width // image.width
+        # Floor division collapses the scaled side to 0 for extreme aspect ratios (a 1x2000 image
+        # scaled to fit 512x512 gives `1 * 512 // 2000 == 0`), and `Image.resize` then fails with
+        # "height and width must be > 0", which names neither the input nor the side that vanished.
+        src_w = width if ratio < src_ratio else max(1, image.width * height // image.height)
+        src_h = height if ratio >= src_ratio else max(1, image.height * width // image.width)
 
         resized = image.resize((src_w, src_h), resample=PIL_INTERPOLATION[self.config.resample])
         res = Image.new("RGB", (width, height))
@@ -451,8 +454,8 @@ def _resize_and_crop(
         ratio = width / height
         src_ratio = image.width / image.height
 
-        src_w = width if ratio > src_ratio else image.width * height // image.height
-        src_h = height if ratio <= src_ratio else image.height * width // image.width
+        src_w = width if ratio > src_ratio else max(1, image.width * height // image.height)
+        src_h = height if ratio <= src_ratio else max(1, image.height * width // image.width)
 
         resized = image.resize((src_w, src_h), resample=PIL_INTERPOLATION[self.config.resample])
         res = Image.new("RGB", (width, height))

tests/others/test_image_processor.py

@@ -308,3 +308,28 @@ def test_vae_image_processor_resize_np(self):
         assert out_np.shape == exp_np_shape, (
             f"resized image output shape '{out_np.shape}' didn't match expected shape '{exp_np_shape}'."
         )
+
+    def test_resize_fill_and_crop_handle_extreme_aspect_ratios(self):
+        """A side must never be scaled down to zero pixels.
+
+        `src_w`/`src_h` are computed with floor division, so scaling a very thin image to fit a
+        square target collapses the short side: `1 * 512 // 2000 == 0`. `PIL.Image.resize` then
+        raises `ValueError: height and width must be > 0`, which names neither the input nor the
+        side that vanished.
+        """
+        image_processor = VaeImageProcessor(vae_scale_factor=1)
+
+        for size in [(1, 2000), (2000, 1), (1, 1)]:
+            image = PIL.Image.new("RGB", size)
+            for resize_mode in ("fill", "crop"):
+                out = image_processor.resize(image, height=512, width=512, resize_mode=resize_mode)
+                assert out.size == (512, 512), f"{size} with resize_mode={resize_mode} gave {out.size}"
+
+    def test_resize_fill_and_crop_unchanged_for_ordinary_images(self):
+        """The clamp must not perturb sizes that were already computed correctly."""
+        image_processor = VaeImageProcessor(vae_scale_factor=1)
+
+        for size in [(64, 64), (900, 3), (3, 900), (1024, 768)]:
+            image = PIL.Image.new("RGB", size)
+            for resize_mode in ("fill", "crop"):
+                assert image_processor.resize(image, height=512, width=512, resize_mode=resize_mode).size == (512, 512)