View Full Version : Image limits in epub?


CW Melbourne
01-06-2013, 09:25 PM
Hi,

I'm working on a large document (about 1,000 pages in paper format) with over 2000 footnotes and 161 images.

Going pretty well, but I'm having an issue with images. I have kept sizes to a minimum and optimized wtih ImageOptim, but they don't seem to all fit in the epub.

I'm aware of the 11MB per chapter limit, and I don't believe I'm breaching that. To test, I removed an image from an earlier chapter, and an extra image now "fits" into the last chapter.

Is there some kind of global limit on images in a document? I can't find one.

Thanks,
Craig.

Toxaris
01-07-2013, 04:01 AM
How do you come up with 11MB per chapter? A lot of older readers have a limit of 300kb per xhtml file (uncompressed), but that is not including images.
I am sure that readers have limits with regards to size of an image due to memory, but I haven't reached it yet. The number of images should not be a problem.

Besides the overal size, there should not be a problem to have 161 images. Just keep your chapters small.

mrmikel
01-07-2013, 07:36 AM
If you are using png, you can try using jpg instead, since unless you are making coffee table sized epubs, there is no need for super hi-res images.

If this came out of a word processing program, you could have endless superfluous styles. Those might need to be gotten rid of. Word processors are designed for paper printing and they don't care how much superfluous junk is in the files.

mzmm
01-07-2013, 11:34 AM
How do you come up with 11MB per chapter?

also curious about this. i know that apple's guidelines suggest that there not be more than 10Mb of images per chapter, but i doubt very much that that's any one else's standard.

if you have photoshop, you can save (non-transparent) images as optimized for web, and then adjust their quality to shrink them further.

you can do pretty much the same using automator with preview (if you have a mac), but the resulting images can be pretty bad quality.

i'm sure there are also other image editors that allow you to batch process...

graycyn
01-07-2013, 03:28 PM
I am sure that readers have limits with regards to size of an image due to memory, but I haven't reached it yet. The number of images should not be a problem.

Recently, as an experiment, given that there is a trend starting towards tablets and phones with higher resolution, I put a couple large images in an epub I made. Both images were large enough for a 400ppi+ display. I believe there already is a phone that either has or will have that resolution.

However, when I loaded the book on my Sony, I was dismayed to see the images not appear at all, just a blank where they were. Book was fine in ADE, and when I decreased image size to 1200 x 2048 pixels, they displayed fine again on the Sony.

So yes, I think reader devices may have some limits on image size.

JSWolf
01-07-2013, 03:52 PM
Also, given multiple screen resolutions from cell phones to tablets to computer screens, you have to make sure your ePub's images are not too large for the screen. So, if you do have large images (resolution), you'll have to make sure they fit the different screen resolutions. I've seen plenty of poorly made ePub where images are not set for different resolution screens and would definitely go partly off the screen.