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Fix: Support 'jpg' format in keras.utils.save_img() #21683

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Fix: Support 'jpg' format in keras.utils.save_img() #21683

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bf4e0ce
Fix save_img(): support 'jpg' format and handle RGBA
utsab345 Sep 20, 2025
b2a5668
Fix save_img: support 'jpg' format (normalize to JPEG) and add tests
utsab345 Sep 20, 2025
d93f3c5
Fix save_img: normalize jpg→jpeg, handle RGBA→RGB, and improve tests
utsab345 Sep 21, 2025
9ab0b4f
Regenerate API directory
utsab345 Sep 21, 2025
b652534
Add save_img to image_utils.py and integration tests for JPG/RGBA han…
utsab345 Sep 25, 2025
4a6a78e
style: fix formatting with format.sh
utsab345 Sep 30, 2025
524252e
Simplify save_img: remove _format, normalize jpg→jpeg, add RGBA→RGB h…
utsab345 Oct 4, 2025
97d00f5
Simplify save_img: remove _format, normalize jpg→jpeg, add RGBA→RGB h…
utsab345 Oct 4, 2025
2a24eaa
fix: use save_format variable to avoid modifying file_format parameter
utsab345 Oct 6, 2025
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15 changes: 15 additions & 0 deletions integration_tests/test_save_img.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
import numpy as np
import os
from keras.utils import save_img

def test_save_jpg_rgb(tmp_path):
img = np.random.randint(0, 256, size=(50, 50, 3), dtype=np.uint8)
path = tmp_path / "rgb.jpg"
save_img(path, img, file_format="jpg")
assert os.path.exists(path)

def test_save_jpg_rgba(tmp_path):
img = np.random.randint(0, 256, size=(50, 50, 4), dtype=np.uint8)
path = tmp_path / "rgba.jpg"
save_img(path, img, file_format="jpg")
assert os.path.exists(path)
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medium

These tests are a good start, but they can be improved. The two test functions are very similar and can be combined into a single parameterized test using pytest.mark.parametrize for better maintainability. Also, the assertions only check for file existence. It would be more robust to load the saved image and verify its content, especially to confirm that RGBA images are correctly converted to RGB.

import os

import numpy as np
import pytest
from keras.utils import img_to_array, load_img, 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)

4 changes: 3 additions & 1 deletion keras/src/utils/image_utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -175,8 +175,10 @@ 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)
if file_format is not None and file_format.lower() == 'jpg':
file_format = 'jpeg'
img = array_to_img(x, data_format=data_format, scale=scale)
if img.mode == "RGBA" and (file_format == "jpg" or file_format == "jpeg"):
if img.mode == "RGBA" and file_format in ["jpeg", "jpg"]:
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high

This change correctly handles file_format='jpg', but it misses the case where file_format is None and the path ends with .jpg. This will cause a crash when saving an RGBA image. The logic can be made more robust by also inspecting the path extension to determine if the output is a JPEG. Also, the condition on line 181 becomes partially redundant after converting jpg to jpeg.

Suggested change
if file_format is not None and file_format.lower() == 'jpg':
file_format = 'jpeg'
img = array_to_img(x, data_format=data_format, scale=scale)
if img.mode == "RGBA" and (file_format == "jpg" or file_format == "jpeg"):
if img.mode == "RGBA" and file_format in ["jpeg", "jpg"]:
_format = file_format
if _format is None and isinstance(path, (str, pathlib.Path)):
_format = pathlib.Path(path).suffix[1:].lower()
if file_format is not None and file_format.lower() == 'jpg':
file_format = 'jpeg'
img = array_to_img(x, data_format=data_format, scale=scale)
if img.mode == "RGBA" and _format in ("jpeg", "jpg"):

warnings.warn(
"The JPG format does not support RGBA images, converting to RGB."
)
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