Commit 855332a

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Fixed SVG-as-text image comparison tests.

SVG-as-text tests make make the figure background transparent, but its colour (i.e. under the transparent mask) is actually black. Before the expected and actual images are compared, they are converted from RGBA to RGB, which makes them both completely black (since the text is also black). As a result, the test passes even if the expected and actual images differ. Not ignoring the transparency layer fixes this problem: discard the transparency layer (if any) only if the image is opaque.

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+814

-753

lines changed

lib/matplotlib
- testing
  - compare.py
- tests/baseline_images/test_bbox_tight
  - bbox_inches_tight_suptile_legend.svg

2 files changed

+814

-753

lines changed

`‎lib/matplotlib/testing/compare.py‎`

Lines changed: 15 additions & 6 deletions

Original file line number	Diff line number	Diff line change
`@@ -371,6 +371,16 @@ def calculate_rms(expected_image, actual_image):`
`371`	`371`	`# 16-bit depth, as Pillow converts these to RGB incorrectly.`
`372`	`372`
`373`	`373`
	`374`	`+def _load_image(path):`
	`375`	`+ img = Image.open(path)`
	`376`	`+ # In an RGBA image, if the smallest value in the alpha channel is 255, all`
	`377`	`+ # values in it must be 255, meaning that the image is opaque. If so,`
	`378`	`+ # discard the alpha channel so that it may compare equal to an RGB image.`
	`379`	`+ if img.mode != "RGBA" or img.getextrema()[3][0] == 255:`
	`380`	`+ img = img.convert("RGB")`
	`381`	`+ return np.asarray(img)`
	`382`	`+`
	`383`	`+`
`374`	`384`	`def compare_images(expected, actual, tol, in_decorator=False):`
`375`	`385`	`"""`
`376`	`386`	`Compare two "image" files checking differences within a tolerance.`
`@@ -435,9 +445,9 @@ def compare_images(expected, actual, tol, in_decorator=False):`
`435`	`445`	`actual = convert(actual, cache=True)`
`436`	`446`	`expected = convert(expected, cache=True)`
`437`	`447`
`438`		`- # open the image files and remove the alpha channel (if it exists)`
`439`		`- expected_image = np.asarray(Image.open(expected).convert("RGB"))`
`440`		`- actual_image = np.asarray(Image.open(actual).convert("RGB"))`
	`448`	`+ # open the image files`
	`449`	`+ expected_image = _load_image(expected)`
	`450`	`+ actual_image = _load_image(actual)`
`441`	`451`
`442`	`452`	`actual_image, expected_image = crop_to_same(`
`443`	`453`	`actual, actual_image, expected, expected_image)`
`@@ -486,9 +496,8 @@ def save_diff_image(expected, actual, output):`
`486`	`496`	`output : str`
`487`	`497`	`File path to save difference image to.`
`488`	`498`	`"""`
`489`		`- # Drop alpha channels, similarly to compare_images.`
`490`		`- expected_image = np.asarray(Image.open(expected).convert("RGB"))`
`491`		`- actual_image = np.asarray(Image.open(actual).convert("RGB"))`
	`499`	`+ expected_image = _load_image(expected)`
	`500`	`+ actual_image = _load_image(actual)`
`492`	`501`	`actual_image, expected_image = crop_to_same(`
`493`	`502`	`actual, actual_image, expected, expected_image)`
`494`	`503`	`expected_image = np.array(expected_image).astype(float)`

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`‎lib/matplotlib/testing/compare.py‎`

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