Issues with 48 bit depth images

[simon]

with MP 1.12.2 on windows 11

Hello,
I saved in 48 bit RGB Tiff (16 bits per chanel) as a PNG image and as a lossless JPEG-XL image. I also reduced the depth of the 48 bit TIFF image to 24 bits and saved it as another TIFF image. The information panel and status bar of XnviewMP say, as expected, that the 48 bit TIFF image has a depth of 48 bits and the 24 bit TIFF image has a depth of 24 bits, but also says that the PNG and JXL images have a depth of 24 bits only. However, the 4 images (TIFF 48, TIFF 24, PNG and JXL) have all the same CRC when using the compare tool.
So it seems that
1) saving a 48 bit image in PNG or lossless JXL is not really lossless but silently reduces the bit depth from 48 to 24 bits
2) the CRC takes only the most significant byte into account when depth is coded on two bytes

thanks
simon

[xnview]

when you open 48bits image, they are reduced to 24bits