Speed up alpha_composite, matrix, negative, quantize

[akx]

Refs #9649, #9675, #9736, #9737, #9738, #9739 (same series, same techniques).

These were a couple lines each, so I figured I'd bundle them into one PR.

[codspeed-hq]

Merging this PR will improve performance by ×3.8

⚠️ 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

⚡ 6 improved benchmarks
✅ 323 untouched benchmarks
🆕 6 new benchmarks
⏩ 2 skipped benchmarks¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	test_invert[1024x1024-LA]	24.9 ms	4.5 ms	×5.6
⚡	test_invert[1024x1024-RGBA]	24.9 ms	4.5 ms	×5.6
⚡	test_invert[1024x1024-RGB]	24.9 ms	4.5 ms	×5.5
⚡	test_invert[1024x1024-L]	6.3 ms	1.2 ms	×5.4
⚡	test_matrix_convert[1024x1024-L-matrix0]	13.5 ms	6.5 ms	×2.1
⚡	test_matrix_convert[1024x1024-RGB-matrix1]	28.9 ms	19.8 ms	+46.1%
🆕	test_alpha_composite[1024x1024-LA-mixed]	N/A	26.7 ms	N/A
🆕	test_alpha_composite[1024x1024-LA-opaque]	N/A	26.8 ms	N/A
🆕	test_alpha_composite[1024x1024-LA-transparent]	N/A	9.6 ms	N/A
🆕	test_alpha_composite[1024x1024-RGBA-mixed]	N/A	26.7 ms	N/A
🆕	test_alpha_composite[1024x1024-RGBA-opaque]	N/A	26.8 ms	N/A
🆕	test_alpha_composite[1024x1024-RGBA-transparent]	N/A	9.6 ms	N/A

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.

---

_{Comparing akx:faster-loops-small (633c164) with main (6590b1b)}

Footnotes

1. 2 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. ↩

[hugovk]

test_alpha_composite is new in this PR, what speedups did you get locally?

[akx]

test_alpha_composite is new in this PR, what speedups did you get locally?

It's actually an expansion of the old test_alpha_composition benchmark that didn't test some of the more interesting cases. Renamed so it doesn't confuse CodSpeed.

---------------------- benchmark 'composition': 6 tests, 2 sources ----------------------
Name (time in us)                                    0013_al0 Min  0014_al1 Min      ΔMin
-----------------------------------------------------------------------------------------
test_alpha_composite[1024x1024-LA-transparent]           557.3750      465.1660    -16.5%
test_alpha_composite[1024x1024-RGBA-transparent]         557.8750      458.8330    -17.8%
test_alpha_composite[1024x1024-LA-mixed]               2,364.1250    2,346.4580     -0.7%
test_alpha_composite[1024x1024-LA-opaque]              2,381.0420    2,357.4580     -1.0%
test_alpha_composite[1024x1024-RGBA-mixed]             2,382.4590    2,327.3750     -2.3%
test_alpha_composite[1024x1024-RGBA-opaque]            2,409.9580    2,370.7500     -1.6%
-----------------------------------------------------------------------------------------