|Even by looking at the thumbnails above, you can see that the png looks lighter in certain areas than do the jpeg and gif formats. The compression of the jpeg format is much more than that of the other two. The jpeg is 32.6 kbs; the gif is 111.2 kbs, while the png is a whopping 372.8 kbs. A png, being not as compressed as the others, yields more fine details.|
Input the jpeg and gif at Image Magick. On the View screen, click on the Identify tab at the top. Scroll down past the red, green and blue color info. Right below that you'll find the number of discrete colors in each image. For the jpeg there are 55,849 colors! But for the gif there are only 256 colors. Quite a difference. A gif will never have more than 256 colors, but it can have less.
Note: Since I started with a jpeg, the png also has 55,849 colors. Had I made an image from scratch, the png version probably would have had as many or more than the jpeg.