I've been seeing for a while that in manga releases coloured pages are in JPG format and the non-coloured pages are generally in PNG format.
I've never really worked with PNG so I don't know much about it. I attempted to use google to find the answer to my topic but to no avail, and anywhere I went to read up on the images didn't provide the information I was looking for.
I'm hoping someone here has experience and can provide an adequate explaination.
PNG is usually used with vector graphics with hard lines ie. manga pages. While jpeg compresses better with gradients and colour heavy images ie. your front page of a manga book.