3a66f4c3-06fa-4389-ab37-45426bd4fef7
commented
4 years ago As part of the Mentored Sprints at PyCon US, Marielle wrote some property-based tests [1] for the colorsys module [2], which found two bugs.
Taking a YIQ color, converting to RGB, and back to YIQ can result in the Y coordinate varying by more 0.1 (where [0, 1] is the range of possible values). For example: (0.0 1.0 2.2204460492503136e-16) -> RGB -> (0.0 1.1102230246251568e-16 1.0)
Taking an RGB color and converting though HSV-RBG-HSV can result in very different saturation values - up to having S1==0 and S2==1. For example: (0.0 1.0 2.2204460492503136e-16) -> RGB -> (0.0 1.1102230246251568e-16 1.0)
You can reproduce additional examples and get error bounds from [3].
[1] https://pyfound.blogspot.com/2020/05/property-based-testing-for-python.html [2] https://docs.python.org/3/library/colorsys.html [3] https://github.com/Zac-HD/stdlib-property-tests/pull/13
rhettinger
serhiy-storchaka
terryjreedy
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields: ```python assignee = None closed_at = None created_at =
labels = ['3.7', '3.8', 'type-bug', 'library', '3.9']
title = 'Catastrophic loss of precision in colorsys module'
updated_at =
user = 'https://github.com/Zac-HD'
```
bugs.python.org fields:
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dependencies = []
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issue_num = 40668
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url = 'https://bugs.python.org/issue40668'
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```