Lossless JPEG detected as Lossy

[MarcusJohnson91]

Using the latest version of the Mac version of MediaInfo from the app store.

You can see the results in this Image

Lossless JPEGs use the following Start of Frame (SOF) markers: SOF3, SOF7, SOF11, SOF15 aka 0xFFC3, 0xFFC7, 0xFFCB, 0xFFCF, respectively.

the sof marker number is the only way to truly tell if an image is lossy or lossless.

the image that was misdetected as lossy can be found here

[ValZapod]

This one uses SOF3. And it is recognized, just not propagated: https://github.com/MediaArea/MediaInfoLib/blob/2f3998512ec3cc6f55c0905eb993bfce95a9a3b2/Source/MediaInfo/Image/File_Jpeg.cpp#L643

SOF3, SOF7, SOF11, SOF15

Last time I checked it should not be zeroes, but Os (Start of). Sigh. https://www.itu.int/rec/T-REC-T.81 and https://www.w3.org/Graphics/JPEG/itu-t81.pdf

SOF3 is Lossless (sequential), Huffman coding

SOF11: Lossless (sequential), arithmetic coding

SOF7: differential lossless process frame marker, Huffman coding

SOF15: differential lossless process frame marker, arithmetic coding

[JeromeMartinez]

Thanks, I fix that when I have some free time.

[ValZapod]

I can give a pull. 0 --> O in two files and add those new markers. Wait a second.

[JeromeMartinez]

I can give a pull

go :)

[ValZapod]

BTW, the image is reported as not conformant by reference implementation. Here is my compile with VS 2022. https://github.com/thorfdbg/libjpeg/issues/61#issuecomment-1034869582

reading a JPEG file failed - error -1038 - invalid stream, found invalid huffman code in entropy coded segment