Increase tolerance so subpixel issue doesn't cause test failure.

mpetroff · mpetroff · commit ad16cb66a39b · 2020-07-12T21:36:56.000Z
There are ten pixels that differ due to how the subpixel calculation is done.
diff --git a/lib/matplotlib/tests/test_image.py b/lib/matplotlib/tests/test_image.py
@@ -732,7 +732,11 @@ def test_log_scale_image():
     ax.set(yscale='log')
 
 
-@image_comparison(['rotate_image'], remove_text=True)
+# Increased tolerance is needed for PDF test to avoid failure. After the PDF
+# backend was modified to use indexed color, there are ten pixels that differ
+# due to how the subpixel calculation is done when converting the PDF files to
+# PNG images.
+@image_comparison(['rotate_image'], remove_text=True, tol=0.35)
 def test_rotate_image():
     delta = 0.25
     x = y = np.arange(-3.0, 3.0, delta)
