I tried to comment before, but my account was suddenly closed and I'm not sure why;
I guess, maybe it was the Cockies in my web browser...
I'm not sure how works the code that compiles and decompiles the images in pixels.
I have also seen differences between the contrast and brightness of the textures, by decompiling and recompiling them.
In my old Photoshop CS2, I can see differences between a color that consists only of 3 channels, RGB; and the same color that consists of 4 channels, CMYK. I see in my Photoshop CS2, that the colors composed by 4 channels, CMYK, are a bit darker because they have added shades of gray or black.
Maybe the truecolour (24-bit)
, have 4 channels with shades of gray or black, like CMYK.
The only method I knew to correct that textures looks too dark, was to use the "Auto Contrast" option
in the Photoshop CS2 program; but I had to correct all the images, one by one...