png2jxl: Convert PNG to lossless JPEG XL with byte-for-byte reconstruction of the original PNG
4 points by ignaloidas
4 points by ignaloidas
The question, of course, is how much bigger (or smaller) the JXL is. I don't see a discussion of this. The next question is whether it survives JXL decode-and-reencode, assuming lossless.
Otherwise one can just store the full PNG in some unused section of the output file.
Both formats are lossless, so image data survives the reverse conversion anyway. The point of this exercise appears to be preserving metadata in a specific way that allows byte-perfect reconstruction of the original PNG.
I meant specifically whether this survives a JXL-to-JXL conversion that is lossless in terms of image data, but may strip metadata (unneeded sections) or simply skip over unrecognised sections.
The reconstruction data lives in a metadata box, so it of course does not survive anything that strips it. The same is true of the JPEG reconstruction that's possible with JXL.