Remove Marshalling code during Color Translation, reduce allocations

[h3xds1nz]

Description

Improves slightly performance and subsequent allocations when subtracting/multiplying or just generally working with Color using a custom profile / ColorContext by removing Marshal code/allocs and simply using stackalloc for the buffer, replacing some dead code (It is obvious Translate method has been rewritten previously) and removing the try/finally block used for unmanaged memory deallocation.

Redundant array inits to 0 have been removed in ICM2Color and also some heap-allocated arrays have been replaced with stack-allocated spans in the call chain.

Last two commits are not included in benchmarks but are pretty straightforward improvements.

Color Subtraction with custom profile

Method	Mean	Error	StdDev	Gen0	Allocated
Marshalled	2.919 ms	0.0460 ms	0.0408 ms	3.9063	79.03 KB
StackAlloc	2.887 ms	0.0555 ms	0.0519 ms	3.9063	78.82 KB

Benchmark code

public Uri sRGB = new("C:\\Windows\\System32\\spool\\drivers\\color\\sRGB Color Space Profile.icm", UriKind.Absolute);

[Benchmark]
public Color Benchmark()
{
    Color x = Color.FromAValues(1.0f, [0.0f, 1.0f, 1.0f], sRGB);
    Color y = Color.FromAValues(0.5f, [0.0f, 0.5f, 1.0f], sRGB);

    return x - y;
}

Multiplication by factor with custom profile

Method	Mean	Error	StdDev	Allocated
Marshalled	1.918 ms	0.0116 ms	0.0097 ms	47.67 KB
StackAlloc	1.915 ms	0.0153 ms	0.0144 ms	47.53 KB

Benchmark code

public Uri sRGB = new("C:\\Windows\\System32\\spool\\drivers\\color\\sRGB Color Space Profile.icm", UriKind.Absolute);

[Benchmark]
public Color Benchmark()
{
    Color x = Color.FromAValues(1.0f, [0.0f, 1.0f, 1.0f], sRGB);

    return x * 0.1f;
}

Raw Translate method call chain

Method	Mean	Error	StdDev	Gen0	Allocated
Marshalled	118.36 ns	1.284 ns	1.201 ns	0.0086	144 B
StackAlloc	22.80 ns	0.430 ns	0.402 ns	0.0043	72 B

Customer Impact

Improved performance, decreased allocations.

Regression

None.

Testing

Build, benchmark, using the code and comparing outputs (addition, subtraction, multiplication).

Risk

Low.

Microsoft Reviewers: Open in CodeFlow

[miloush]

LGTM

[miloush]

using the code and comparing outputs (addition, subtraction, multiplication).

Did you test it on multichannel color contexts?