Pages file doubles on export to .epub

Question

When I export a Pages document to .epub, the file size doubles. I have a lot of .png images, and I have compressed them, but it still goes from a 12MB Pages file to a 24MB .epub file. What is happening and how do I keep my file to under 20 MB?

Answer 1

Any ideas on how to get my images down to the size to which they were compressed? Or does Stuffit (and Pages) somehow know what the original file size was and are using that to calculate the size of the images?
Sounds like you are being caught up too much in a numbers game here. The only true measure is the final amount of space taken up by the ePUB package which is, essentially, just a zipped package of files that are basically text and images.
Applications and utilities tend to differ in how they report a file's size. For instance, my cover JPEG files are 1.39 MBs (the decompressed file size) according to one application, 472 KBs of disk space (data + header + container with or without empty space allocation) according to the OS Finder, but only contains about 351 KBs (compressed data) according to yet another application--all readings for the same file as stored in the Pages package. When converted to a PNG at 2/3 the original dimensions (or 4/9 the surface area) file and embedded in the ePUB export, the same applications/utilities now report file sizes of 606 KBs, 496 KBs, and 493 KBs respectively. However, now we are comparing apples and oranges since we have added the complication of changing the compression format from JPEG (which most applications allow you to easily vary the amount of compression drastically) to PNG (which none of my normal applications allow me the vary the compression).
My basic recommendation is to use high quality/low compression images in the project and simply let things fall as they may during the export process. Of course, since I sometimes include movies in my ePUBs, my exports sometimes tend to be somewhat large. If you cannot bare to live with the file sizes as converted/exported by Pages, and, if you have the capability to actually create PNG files with a variable compression ratio, then, by all mens, simply replace the Pages generated files in the expanded ePUB folder with your own files having the exact same names and extensions, re-ZIP the folder, and change the file extension back to ".epub" to use your manually modified media/content.