Jpeg encoder complete rewrite

[br3aker]

Prerequisites

• [x] I have written a descriptive pull-request title
• [x] I have verified that there are no overlapping pull-requests open
• [x] I have verified that I am following the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules :cop:.
• [x] I have provided test coverage for my change (where applicable)

New architecture

Jpeg encoder now have a brand new architecture which allows us to define encoding 'configs' like this:

// YCbCr 4:1:0
new JpegFrameConfig(
    JpegColorSpace.YCbCr,
    JpegEncodingColor.YCbCrRatio410,
    new JpegComponentConfig[]
    {
        new JpegComponentConfig(id: 1, hsf: 4, vsf: 2, quantIndex: 0, dcIndex: 0, acIndex: 0),
        new JpegComponentConfig(id: 2, hsf: 1, vsf: 1, quantIndex: 1, dcIndex: 1, acIndex: 1),
        new JpegComponentConfig(id: 3, hsf: 1, vsf: 1, quantIndex: 1, dcIndex: 1, acIndex: 1),
    },
    yCbCrHuffmanConfigs,
    yCbCrQuantTableConfigs)

Which allow us to define any allowed subsampling setup or even a 'custom' scenario with any number of components if user needs to. This API is internal for now - user can only choose encoding mode via enum which we had a long time ago. Maybe one day we can make it public - who knows.

Due to this change: https://github.com/SixLabors/ImageSharp/issues/1713 is resolved and https://github.com/SixLabors/ImageSharp/issues/1476 is resolved.

It would also be fairly easy to implement optimized huffman tables or progressive encoding with current architecture.

API changes

1. All of these encoding modes are implemented now:

YCbCrRatio420 = 0,
YCbCrRatio444 = 1,
YCbCrRatio422 = 2,
YCbCrRatio411 = 3,
YCbCrRatio410 = 4,
Luminance = 5,
Rgb = 6,
Cmyk = 7,
Ycck = 8,

2. Grayscale encoding now has a vectorized color conversion which gained a lot of performance.

~~3. I've removed Ycck encoding simply because it's not popular and we didn't support it anyway (we still can decode YccK though). This issue is partially done: https://github.com/SixLabors/ImageSharp/issues/808~~

4. Added non-interleaved encoding for any color type.

Performance

Encoder got a bit slower but I think new architecture's worth it - we were really fast before, now we are still fast enough.

Main branch

Method	TargetColorSpace	Quality	Mean
Benchmark	Luminance	75	6.923 ms
Benchmark	Rgb	75	12.116 ms
Benchmark	YCbCrRatio420	75	6.484 ms
Benchmark	YCbCrRatio444	75	8.263 ms
Benchmark	Luminance	90	7.046 ms
Benchmark	Rgb	90	13.349 ms
Benchmark	YCbCrRatio420	90	6.714 ms
Benchmark	YCbCrRatio444	90	9.198 ms
Benchmark	Luminance	100	9.057 ms
Benchmark	Rgb	100	19.099 ms
Benchmark	YCbCrRatio420	100	10.194 ms
Benchmark	YCbCrRatio444	100	15.372 ms

PR

Method	TargetColorSpace	Quality	Mean
Benchmark	Luminance	75	4.618 ms
Benchmark	Rgb	75	12.543 ms
Benchmark	YCbCrRatio420	75	6.639 ms
Benchmark	YCbCrRatio444	75	8.590 ms
Benchmark	Luminance	90	5.456 ms
Benchmark	Rgb	90	13.447 ms
Benchmark	YCbCrRatio420	90	7.218 ms
Benchmark	YCbCrRatio444	90	9.150 ms
Benchmark	Luminance	100	6.731 ms
Benchmark	Rgb	100	19.831 ms
Benchmark	YCbCrRatio420	100	10.541 ms
Benchmark	YCbCrRatio444	100	15.345 ms

[br3aker]

Need to write a ton of tests now....

[br3aker]

Update

Added YccK encoding so this PR completely resolves https://github.com/SixLabors/ImageSharp/issues/808.

[br3aker]

Hmm, this failed test passes on my local machine with .net6 and fails only on macos on .net7. Wondering if this is the same problem as in https://github.com/SixLabors/ImageSharp/issues/2117.

[brianpopow]

Hmm, this failed test passes on my local machine with .net6 and fails only on macos on .net7. Wondering if this is the same problem as in #2117.

I have not seen issue #2117 on mac yet, only on windows so far, but it could be related.

I will restart the CI to see, if it was a fluke or always happens.

[br3aker]

I will restart the CI to see, if it was a fluke or always happens.

Looks like it's not a fluke. I'll start writing tests this week for this PR and try to add debug checks for memory access, maybe it's related to some out of bounds index access.

[br3aker]

Finally had a moment to finish this:

1. All colors are supported for encoding
2. Implemented non-interleaved encoding aka a separate scan for each component
3. Added tests and removed obsolete benchmark tests - we have proper benchmarks for that
4. Restored ProfilingSandbox.cs

@JimBobSquarePants @brianpopow

[br3aker]

Looks like Skew tests fails on net7 is still a thing. Everything else should be working just fine. I've added tests for all new output color types with a very precise tolerance.

New encoder architecture mirrors decoder architecture. It should allow us to write encoding expansions like optimized huffman table generation or progressive encoding.

P.S. Please be advised that this PR is a breaking change due to new jpeg output color type enum.

[JimBobSquarePants]

Very exciting! Will review this asap.

[br3aker]

Looks like I've messed up linked issues, here's the complete list of what's resolved by this PR:

1. https://github.com/SixLabors/ImageSharp/issues/1476 - all color conversions now support scalar/vector/avx paths
2. https://github.com/SixLabors/ImageSharp/issues/808 - all output color types are supported
3. https://github.com/SixLabors/ImageSharp/issues/1713 - only required quantization table(s) is(are) written
4. https://github.com/SixLabors/ImageSharp/issues/1238 - CMYK input jpeg now should be resaved to CMYK output jpeg if not explicitely overriden in encoder settings