Png's are decoding wrong after 1.0.0-alpha-000061 about imagesharp

[KLuuKer]

it could also be a issue with the png itself, because if i resave the image with irfanview it multithread decodes & encodes correctly

[JimBobSquarePants]

Hmmmm... Probably the ArrayPool stuff again. Odd, it really doesn't seem to be threadsafe.

Would you be able to fork the repo and conduct your tests with a reverted decoder? I'll test myself when I can.

[KLuuKer]

Well i checked and the ArrayPool is definitely thread safe

BUT you will eventually get MORE bytes than you asked for. the docs say it will return a array of MINIMAL the specified length. so great care must be taken in using the bytes that are returned by the pool.

https://github.com/JimBobSquarePants/ImageSharp/blob/master/src/ImageSharp/Formats/Png/PngDecoderCore.cs#L338
i replaced those pool rent's with new byte[this.bytesPerScanline];
and that worked, so the issue would probably be in the processing of
https://github.com/JimBobSquarePants/ImageSharp/blob/master/src/ImageSharp/Formats/Png/PngDecoderCore.cs#L365
as that doesn't have the correct length passed to it

sorry if it sounds like i'm ranting, it must be hard trying to keep your head straight with this huge amount of code

[JimBobSquarePants]

Och not at all, at least it looks like it should be an easy fix then. Would you like to give it a go? You have the advantage of tests that work.

I really need to beef up my parallel test.