Avoid an extra copy/resample if imshow input has no alpha #27562
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jklymak
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Dec 23, 2023
This is probably the best we can do to fix matplotlib#27554 at this time, without delving into re-writing the Agg resampler (which, as the Python code notes, does require RGBA.)
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This is in the |
ksunden
reviewed
Jan 9, 2024
| # No need to resample alpha or make a full array; NumPy will expand | ||
| # this out and cast to uint8 if necessary when it's assigned to the | ||
| # alpha channel below. | ||
| output_alpha = (255 * alpha) if A.dtype == np.uint8 else alpha |
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shouldn't it be multiplying by 255 if it is a float, rather than if it is a uint8?
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alpha is always a 0-1 float; if the data is uint8, then output alpha must be 0-255 instead.
ksunden
approved these changes
Jan 10, 2024
jklymak
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Jan 10, 2024
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PR summary
This is probably the best we can do to fix #27554 at this time, without delving into re-writing the Agg resampler (which, as the Python code notes, does require RGBA.)
Also adds a test, as it appears that nothing checked an RGB input with transparent
alpha(and my original suggestion from #27554 (comment) using 255/1.0 passed tests even though it didn't work.)PR checklist