Discard the transparency layer (if any) only if the image is completely opaque.

tfpf · tfpf · commit 5d127c48a62e · 2022-07-02T17:17:11.000+05:30
diff --git a/lib/matplotlib/testing/compare.py b/lib/matplotlib/testing/compare.py
@@ -373,7 +373,9 @@ def calculate_rms(expected_image, actual_image):
 
 def _load_image(path):
     img = Image.open(path)
-    return np.asarray(img if img.mode == "RGBA" else img.convert("RGB"))
+    if img.mode == "RGBA" and img.getextrema()[3][0] < 255:
+        return np.asarray(img)
+    return np.asarray(img.convert("RGB"))
 
 
 def compare_images(expected, actual, tol, in_decorator=False):
