DDS: speed up reading of uncompressed images #3463
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Previous code was doing ioread one pixel at a time. Change it to read one scanline at a time, similar to e.g. how BMP reader does it. On a 8192x8192 rgba8 image (256MB), on Apple M1 Max "iinfo --hash" time goes from 2.19s down to 0.65s, and is now similar to the time it takes on an uncompressed TIF or BMP image.
lgritz
approved these changes
Jul 4, 2022
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Description
Previous code was doing ioread one pixel at a time. Change it to read one scanline at a time, similar to e.g. how BMP reader does it.
On a 8192x8192 rgba8 image (256MB), on Apple M1 Max
iinfo --hashtime goes from 2.19s down to 0.65s, and is now similar to the time it takes on an uncompressed TIF (0.52s) or BMP (0.71s) image.Tests
No need for new tests, existing DDS test coverage should be fine.
Checklist:
have previously submitted a Contributor License Agreement
(individual, and if there is any way my
employers might think my programming belongs to them, then also
corporate).
(adding new test cases if necessary).