Recently I published an image heavy Kindle title and found that it had quite a large file size. The culprit of course was the number of images. Kindle books only support either the .JPG or .GIF image format, so using highly optimized .PNGs was out of the question.
As I was using Jutoh to write my book, I didn’t have access to the image files used by Jutoh once they had been imported. It would have taken days to reinsert every image file after optimizing them. The quickest way to optimize all images that I found was to compile the book to a .mobi file, use KindleUnpack to unpack the .mobi file, open the zip file containing the source files, optimize all the .gif images using Trout Image Optimizer and then finally open the content.opf file in KindlePreviewer which automatically compiles a new .mobi file with the optimized images.