If colour is involved then page size shoots up...
JPEG gets the page size down quite a bit but its
effects on text are really quite bad.
Something probably should be said for GIF.
This format is good for images with 16 or 256 different levels of color
and won't spatially filter (IE distort high freqency detail) anything when
the number or colors is within these bounds. It's always good when
you can discretize the number of saved colors of the image to the
number of printed colors. For example B&W as two levels, and B&W
with a two color illustration as 4 levels, otherwise known as a 4 color
lookup table. All of these things can be done lossless with GIF.
John A.