Add support of ReadOnlySequence and IBufferWriter

[DanilovSoft]

Description

MagickImage recently began support initialization from ReadOnlySpan<byte>, which is great! But some times source memory can be fragmented and to prevent heap allocation it would be nice to have initialization from ReadOnlySequence<byte>. Also writing output is still restricted to Stream and coresponding to Span's it would be good to have overload for IBufferWriter<byte>.

Proposal

Add constructor overload MagickImage(ReadOnlySequence<byte> data) and coresponding Read overload.
Add Write overload MagickImage.Write(IBufferWriter<byte> buffer).

System Configuration

• Magick.NET version: Magick.NET-Q16-x64 8.1.0
• Environment (Operating system, version and so on): Windows 10 x64

[dlemstra]

It looks like ReadOnlySequence<byte> is not always a noncontiguous "byte array" and that is required for the native code of Magick.NET. But it is probably possible to add support for an IBufferWriter<byte>.

[dlemstra]

Just realized it might also be possible to use the ReadOnlySequence<byte>, will need to run some experiments.

[dlemstra]

Support for both ReadOnlySequence<byte> and IBufferWriter<byte> will become available in the next release.

[DanilovSoft]

An infinite loop occurs in ReadOnlySequenceWrapper.Read when there are more than one segments in ReadOnlySequence.

[dlemstra]

I added a unit test for this to make sure this works but it I only tested this with 1 byte sequences. This probably fails with sequences of a specific size will add a test for this and get this fixed.

edit: I am working on a fix and I will publish a new release in a couple hours.