René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"check_figures_equal does not account for changed background colors in comparison","articleBody":"\u003c!--To help us understand and resolve your issue, please fill out the form to the best of your ability.--\u003e\r\n\u003c!--You can feel free to delete the sections that do not apply.--\u003e\r\n\r\n### Bug report\r\n\r\n**Bug summary**\r\n\r\nWhen `check_figures_equal` is used as a decorator, the default behavior is to remove any background color during `savefig`, so plots which should have a different background color can't be properly compared.\r\n\r\nFor example, code that should produce a figure with a black background and the reference figure would both be saved as a white background.\r\n\r\n**Code for reproduction**\r\n\r\n```python\r\nfrom matplotlib.testing.decorators import check_figures_equal\r\n\r\ndef create_test_figure_black_background(fig):\r\n    axis = axis = fig.subplots()\r\n    fig.set_facecolor('black')\r\n    axis.bar(\r\n        [0, 1, 2, 3, 4],\r\n        [4, 5, 7, 9, 2],\r\n        color=[\"red\", \"blue\", \"black\", \"yellow\", \"white\"],\r\n        edgecolor=\"black\",\r\n    )\r\n\r\n\r\n@check_figures_equal(extensions=[\"png\"])\r\ndef test_dark_background(test_figure, reference_figure):\r\n\r\n    ref_ax = reference_figure.subplots()\r\n    ref_ax.bar(\r\n        [0, 1, 2, 3, 4],\r\n        [4, 5, 7, 9, 2],\r\n        color=[\"red\", \"blue\", \"black\", \"yellow\", \"white\"],\r\n        edgecolor=\"black\",\r\n    )\r\n\r\n    create_test_figure_black_background(test_figure)\r\n```\r\n\r\n**Actual outcome**\r\n\r\nrunning with pytest shows a passing test, even though the test_fig should have a black background and the reference figure has a white background.  These are both changed to white in `savefig`\r\n\r\n```\r\nC:\\Users\\Andrew\\Workspace\\TripleAgent\u003e pytest .\\triple_agent\\ -k test_dark_background\r\n================================================================ test session starts =================================================================\r\nplatform win32 -- Python 3.7.5, pytest-4.5.0, py-1.8.0, pluggy-0.9.0\r\nplugins: xdist-1.29.0, forked-1.0.2, cov-2.7.1\r\ncollected 1112 items / 1111 deselected / 1 selected\r\n\r\ntriple_agent\\tests\\test_plot_types.py .                                                                                                         [100%]\r\n\r\n===================================================== 1 passed, 1111 deselected in 2.38 seconds ======================================================\r\n```\r\n\r\n**Expected outcome**\r\n\r\nExpect that backgrounds are preserved so that functionality for backgrounds can be tested.\r\n\r\nhttps://github.com/matplotlib/matplotlib/pull/15111 would likely solve the issue.\r\n\r\n**Matplotlib version**\r\n\u003c!--Please specify your platform and versions of the relevant libraries you are using:--\u003e\r\n  * Operating system: Win10\r\n  * Matplotlib version: 3.1.0\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): TkAgg (i think?)\r\n  * Python version: 3.7.5\r\n  * Jupyter version (if applicable):\r\n  * Other libraries: \r\n\r\n\u003c!--Please tell us how you installed matplotlib and python e.g., from source, pip, conda--\u003e\r\n\u003c!--If you installed from conda, please specify which channel you used if not the default--\u003e\r\n\r\n","author":{"url":"https://github.com/andrewzwicky","@type":"Person","name":"andrewzwicky"},"datePublished":"2020-01-20T23:04:56.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/16275/matplotlib/issues/16275"}