Support TIFFs utilizing ExtraSamples

[dvdgutzmann]

First of all, I want to tell you how much we appreciate your work. ImageSharp is a great library and we have never had a problem with it. We recently upgraded to v2 to take advantage of the TIFF support.

When loading some TIFFs via Image.Load(stream, out var imageFormat), an exception is thrown stating ExtraSamples is not supported . We understand that ExtraSamples are a way to achieve transparency in TIFFs.

[brianpopow]

As the exception states, we do not support ExtraSamples yet. You can find an overview of what is supported and what not in the ReadMe in the tiff format folder: TiffReadMe

Any help with implementing missing features is very welcome.

[dvdgutzmann]

Thank you for pointing out the ReadMe. Unfortunately, image processing is not exactly our field of expertise, we probably wouldn't be much help.

[JimBobSquarePants]

It's basically a case of read the spec, implement the spec when it comes to implementing image formats.

[brianpopow]

With PR #2062, #2047 and #2037 merged to main, we support now decoding Tiff images with alpha data. It can be tried out via our nightly builds.

edit: with 2.1.0 released, its now available via the nuget feed