yigolden/jpeglibrary

JPEG decoder, encoder and optimizer implemented in C#.

jpeglibrary's Issues

Any interest in a pull request to fix a parsing bug in single component files.

I think I have run into and fixed a bug.

In a single component JPEG file the horizontal and vertical sampling values are ignored. See ITU T81 Section A.2.2

When Ns = 1 (where Ns is the number of components in a scan), the order of data units within a scan shall be left-to-right
and top-to-bottom, as shown in Figure A.2. This ordering applies whenever Ns = 1, regardless of the values of H1 and V1.

I have found a number of single component files with H1 and V1 not equal to one in the wild, and JpegLibrary chokes on them. The image below is one such image

I found that I can make them parse by forcing H1 and V1 to 1 in all single component files. In JpegFrameComponentSpecificationParameters I added a totalComponents parameter to both of the TryParse methods. This allows me to force H1 and V1 to 1 if there is only a single component.

        byte quantizationTableSelector = buffer[2];
        byte samplingFactor = buffer[1];
        byte identifier = buffer[0];

        if (totalComponents == 1) samplingFactor = 0x11;

This now parsers all of the JPEGs that I tested it on.

If you would welcome it, I would be happy to prepare a pull request that implements this change.

Dependency Mix

Hello,
I really appreciate the library and it was a real life saver because it implements so many encoding options. One problem I found was that it apparently uses two different versions of "System.Runtime.CompilerServices.Unsafe" (4.06.26919.2 and 4.700.20.12001). While not a breaking bug it led to some problems in one of our projects.
Many thanks and Kind Regards,
Dominik

SOF3 encoding support?

Thanks for sharing this software. I had a bit of trouble getting it to work with the "Greaterthan8bit" example output buffer with a DNG file as input but I was able to kinda patchwork my way through it. See my RawBayer2DNG project if you're curious. Had to do some unsafe casting to ushort for example so that values would be correctly interpreted.

Was wondering if it would be possible to implement SOF3 encoding as well or if you can recommend anything that can be used in C# that does SOF3 encoding. Cheers