Previous 1 2 Next 15 Replies Latest reply: Apr 9, 2013 5:06 PM by vinnyvg
tndom Level 1 (10 points)

Hello all.


Could anyone please enlighten me to the best practice image specifications for Multi-Touch books made through iBooks Author? I've looked through the iBookstore Asset Guide and iBooks Author support but can't find anything that specifically applies to .iBooks, just EPUBs. I see that, there, the maximum is 2 million pixels, but does this still apply to .iBooks?


The iPad with Retina's resolution is 2048x1536 (over 3 million pixels), so surely it wouldn't make sense to restrict iBook images in such a way?


Any knowledge welcome.

  • K T Level 7 (23,700 points)

    Don't confuse hardware specs with deployment support.


    With any image, ppi/dpi of 72 is sufficient resolution. Anything more is wasted and has nothing do with with H X W.

  • tndom Level 1 (10 points)

    You're right, that is confusing it somewhat, mostly because my knowledge of the area isn't 100%! Would you be so kind as to briefly explain why 72dpi is sufficient when the resolution of the screen is so much higher? I don't understand.


    Would, say, a 100 x 100 image at 72dpi not be of a lesser quality than a 1,000 x 1,000 image at 72dpi?


    Where and why does the pixel limit come into all of this?

  • K T Level 7 (23,700 points)

    >Would, say, a 100 x 100 image at 72dpi not be of a lesser quality than a 1,000 x 1,000 image at 72dpi?




    72 is 72. Try it on your own devices and see.


    As a developer (and ebook author), I'm quoting Apple engineers, whom I've come to trust in these things - don't get hung up on the hardware.


    >Where and why does the pixel limit come into all of this?


    Not sure I understand that question, as 'pixel limit' isn't a technical term I'm aware of, sorry.


    Again, do your own testing with your own images on your own devices. Don't let concepts or precepts get in the way of seeing for for me.

  • tndom Level 1 (10 points)

    By 'pixel limit' I mean that, under the guidance of Apple's documentation, the maximum size a square image should be is 1414x1414 (just under 2 million pixels). Why is this guidance in place?

  • K T Level 7 (23,700 points)

    You'd need to ask Apple directly for such clarification on their 'guidance', not me, sorry.


    My opinion is that you may be conflating certain info and/or differently interpreting certain parmeters/definitions.


    My image editing tools will help/allow me to make any H x W image, 72 dpi/ppi. Suggest you use something that works in that capacity as well.

  • tndom Level 1 (10 points)



    Thank you for your time and replies.

  • Tom Gewecke Level 9 (76,380 points)

    K T wrote:


    >Where and why does the pixel limit come into all of this?


    Not sure I understand that question, as 'pixel limit' isn't a technical term I'm aware of, sorry.



    Some folks are getting rejections because of the "pixel limit" it seems:


  • K T Level 7 (23,700 points)

    I can easily image bloated images receiving pushback, with this or that limit quoted to help justify a rejection.

  • AuthorPaige Level 1 (0 points)

    I too am confused. If you take the standard cover size the height is 1.5 times the width. If the width is required to be 1400 or larger then the height must be 2100 or larger. This makes the total just under 3 million. What am I missing here? I have tried resizing to everything, either my width is not wide enough or my total exceeds 2 million. I get rejected every time. Does my image need to be rotated sideways or something? I do not understand how to make this cover work in these guidelines.

  • vinnyvg Level 4 (1,865 points)

    There is a huge amoount of information relating to  images sizes for use with iBA and iPad display.

    Look at Apples RETINA specs in the store.  here is a copy 2048-by-1536 resolution at 264 pixels per inch.

    (ppi)    to confound you, Apple set a 2 megapixel limit om images  size!  And remember this size related to a fullpage display.


    I suggest you search the forum post and read up on the seeming conflicting information.

  • tndom Level 1 (10 points)

    Hello all. I have just got off the phone with iBookstore Support with my questions on this matter.


    I will split up my explanation of what they said to me into three separate parts:


    The cover marketing image: there is no limit on this image. This is the image that is shown on the storefront etc. Apple recommends a minimum of 2400 pixels along the shorter axis and the use of RGB color mode for this.


    The front cover image: there is a 2 million pixel limit on this image. This is what shows when your book first loads.


    The interior images: the nice chap I spoke to said he believed there was no restriction on these images for Multi-Touch iBooks. However, he stated that there may be a rejection if there was an unusually large image(s) that might impact on the download time and/or speed of the entire book asset. But the delivery team would work with you to solve this. In the meantime, he advised me to just go ahead and 'make the book how you want it', but check the overall book asset size before delivery to reflect on this decision.


    So there we have it! I will now probably deliver my images at 2048x1536 (or similar) for optimal clarity while keeping an eye on acceptable image size.

  • AuthorPaige Level 1 (0 points)

    Yeah. It looks like the cover art you upload separately is only used in the iBookstore. The image you use as cover  art in your actual book is limited to the 2M pixels. I am not sure why they cannot just say that somewhere. Their errors should include that. Lots of people will not know the difference between the cover they use and the cover we use in actual book.

  • K T Level 7 (23,700 points)

    There could be better verbiage, I agree.


    In iBooks Author, the first page is captured and used as the 'cover' automatically when using it's Publish to the store menu, then handed off to iTunes Producer, where you can use it as-is, or change to something else if you desire. If you change it, you need to be aware of the specs (see blurb below)


    If you create a standard epub, say from Pages, and then use iTunes Producer, adding cover art is manual.


    From iTunes Producer:



    These finer points for covers are covered in multiple areas, ranging from several existing threads here to the blurb to the iTunes Producer Guide to Apple tech notes, and this email from Apple last year which the helpful Apple staffer doubtlessly quoted:


    Cover Images

    We are changing the minimum size for cover images. Cover images should now be 1400 pixels wide, in the RGB color space, and delivered as JPEG files. The new minimum size for cover images will be a requirement starting this August. Books already available on the iBookstore do not need to be redelivered.

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