minor optimisations

[AntonyCorbett]

Set of small optimisations to reduce SOH allocations on hot paths. Provides ~20% reduction in time to process very large SVG data.

[AntonyCorbett]

@wieslawsoltes I closed the single PRs and placed all changes in this one.

[wieslawsoltes]

@AntonyCorbett Could you add benchmarks for those optimizations' https://github.com/svg-net/SVG/tree/master/Tests/Svg.Benchmark

[AntonyCorbett]

PathTypes allocates byte[] each time in this loop

[AntonyCorbett]

Reduces string allocation in SOH, improving perf

[AntonyCorbett]

Unnecessary allocation to array

[AntonyCorbett]

@wieslawsoltes

@AntonyCorbett Could you add benchmarks for those optimizations' https://github.com/svg-net/SVG/tree/master/Tests/Svg.Benchmark

My simple test involves the use of a 30MB SVG file (so not sure that you would want me to include it). The benchmark code is as follows:

[Benchmark]
public void SvgDraw_BigRiver()
{
    using var stream = Open("__BigRiver.svg");
    var doc = SvgDocument.Open<SvgDocument>(stream);
    var bmp = doc.Draw();
    using MemoryStream ms = new MemoryStream();
    bmp.Save(ms, ImageFormat.Jpeg);
}

Results for non-optimised code:

Results for optimised code:

[wieslawsoltes]

@wieslawsoltes

@AntonyCorbett Could you add benchmarks for those optimizations' https://github.com/svg-net/SVG/tree/master/Tests/Svg.Benchmark

My simple test involves the use of a 30MB SVG file (so not sure that you would want me to include it). The benchmark code is as follows:

[Benchmark]
public void SvgDraw_BigRiver()
{
    using var stream = Open("__BigRiver.svg");
    var doc = SvgDocument.Open<SvgDocument>(stream);
    var bmp = doc.Draw();
    using MemoryStream ms = new MemoryStream();
    bmp.Save(ms, ImageFormat.Jpeg);
}

Results for non-optimised code:

Results for optimised code:

Looking great 👍

Btw what I meant for benchmark is to be more granular and cover just one optimization, you can see the existing benchmarks are done that way. It helps preventing regression and easier finding what those caused.

[H1Gdev]

Please remove spaces.