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TST: Convert all non-RGB(A) images to RGBA #32212

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Merged
timhoffm merged 1 commit into from
Aug 16, 2026
+10 −5
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TST: Convert all non-RGB(A) images to RGBA #32212

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15 changes: 10 additions & 5 deletions lib/matplotlib/testing/compare.py
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Original file line number Diff line number Diff line change
Expand Up @@ -401,11 +401,16 @@ def calculate_rms(expected_image, actual_image):

def _load_image(path):
img = Image.open(path)
# In an RGBA image, if the smallest value in the alpha channel is 255, all
# values in it must be 255, meaning that the image is opaque. If so,
# discard the alpha channel so that it may compare equal to an RGB image.
if img.mode != "RGBA" or img.getextrema()[3][0] == 255:
img = img.convert("RGB")
if img.mode != "RGB":
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# If we have anything other than RGB(A) (e.g., a paletted image), convert it
# to RGBA.
if img.mode != "RGBA":
img = img.convert("RGBA")
# In an RGBA image, if the smallest value in the alpha channel is 255, all
# values in it must be 255, meaning that the image is opaque. If so, discard the
# alpha channel so that it may compare equal to an RGB image.
if img.getextrema()[3][0] == 255:
img = img.convert("RGB")
return np.asarray(img)


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