Speed up some conversions

[akx]

Experiments to speed up the other conversions didn't really yield fruit.

[hugovk]

Rebased following benchmark image update: #9831.

Edit: or not, due to conflict :)

Merging main in instead.

[codspeed-hq]

Merging this PR will improve performance by 71.2%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 4 improved benchmarks
✅ 551 untouched benchmarks
⏩ 335 skipped benchmarks¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	test_convert[1237x811-P-RGBA]	9.9 ms	4.9 ms	×2
⚡	test_convert[1237x811-P-RGB]	9.3 ms	5.1 ms	+81.24%
⚡	test_convert[1237x811-PA-RGB]	10.7 ms	6.5 ms	+64.05%
⚡	test_convert[1237x811-PA-RGBA]	11.3 ms	7.9 ms	+42.27%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing akx:faster-convert-x (b7e834c) with main (c8c74c8)}

Footnotes

1. 335 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩