Fix: Support 'jpg' format in keras.utils.save_img()

.gitignore

@@ -6,6 +6,7 @@ __pycache__
 **/.vscode test/**
 **/.vscode-smoke/**
 **/.venv*/
+venv
 bin/**
 build/**
 obj/**

integration_tests/test_save_img.py

@@ -0,0 +1,27 @@
+import os
+
+import numpy as np
+import pytest
+
+from keras.utils import img_to_array
+from keras.utils import load_img
+from keras.utils import save_img
+
+
+@pytest.mark.parametrize(
+    "shape, name",
+    [
+        ((50, 50, 3), "rgb.jpg"),
+        ((50, 50, 4), "rgba.jpg"),
+    ],
+)
+def test_save_jpg(tmp_path, shape, name):
+    img = np.random.randint(0, 256, size=shape, dtype=np.uint8)
+    path = tmp_path / name
+    save_img(path, img, file_format="jpg")
+    assert os.path.exists(path)
+
+    # Check that the image was saved correctly and converted to RGB if needed.
+    loaded_img = load_img(path)
+    loaded_array = img_to_array(loaded_img)
+    assert loaded_array.shape == (50, 50, 3)

keras/src/utils/image_utils.py

@@ -175,13 +175,35 @@ def save_img(path, x, data_format=None, file_format=None, scale=True, **kwargs):
         **kwargs: Additional keyword arguments passed to `PIL.Image.save()`.
     """
     data_format = backend.standardize_data_format(data_format)
+
+    # Determine output format
+    _format = file_format
+    if _format is None and isinstance(path, (str, pathlib.Path)):
+        suffix = pathlib.Path(path).suffix.lower()
+        if suffix.startswith("."):
+            suffix = suffix[1:]
+        _format = suffix
+
+    # Normalize jpg → jpeg for both file_format and _format
+    if file_format is not None and file_format.lower() == "jpg":
+        file_format = "jpeg"
+    if _format is not None and _format.lower() == "jpg":
+        _format = "jpeg"
+
+    # Convert array to PIL Image
     img = array_to_img(x, data_format=data_format, scale=scale)
-    if img.mode == "RGBA" and (file_format == "jpg" or file_format == "jpeg"):
+
+    # Handle RGBA → RGB if saving to JPEG
+    if img.mode == "RGBA" and (_format in ("jpeg", "jpg")):
         warnings.warn(
-            "The JPG format does not support RGBA images, converting to RGB."
+            "The JPEG format does not support RGBA images, converting to RGB."
         )
         img = img.convert("RGB")
-    img.save(path, format=file_format, **kwargs)
+
+    # Finalize save format (explicit file_format wins)
+    save_format = file_format if file_format is not None else _format
+
+    img.save(path, format=save_format, **kwargs)
 
 
 @keras_export(["keras.utils.load_img", "keras.preprocessing.image.load_img"])