One of the unexpected and strange challenges of designing a book with iBooks Author (and with most of the other tools and e-bookstores available) is designing the book’s cover.
iBooks Author is a phenomenal yet (sometimes) extremely frustrating piece of software. In typical Apple fashion, menus and options have been simplified to the point where flexibility appears to be lost. In the end though, iBooks Author will do most everything you want it to; it just takes a bit of finesse and trial and error.
This post focuses on the creation of art/photo books that require full screen display of images at high quality levels on retina display iPads. Here is what I have learned when it comes to formatting this type of images for iBooks Author:
- Don’t believe what you read: there is an immense amount of misinformation about image formatting for iBooks Author. Apple itself seems to confuse the issues with their rather vague or imprecise answers in their users forum.
- Believe this: if you want your images to display full screen on any iPad (including the retina display iPad) with the best possible resolution and quality, follow these guidelines:
- All images except the book cover should be 2048 x 1496 pixels.
- Your book cover should be 1004 x 768 pixels.
- Sharpening is not necessary.
- sRGB or Adobe RGB color mode
- Save images as JPEGs, maximum quality.
- To center your images and display full screen, use the following parameters in the metrics panel of the Inspector: size at 1024 pixels in width (this will automatically adjust the height to 748 pixels) and position at zero for both the X and Y axis.
Let’s look at a few of these guidelines in more details.
My guidelines are designed to maximize the image quality while remaining below the maximum image size allowed by Apple. These settings will allow for a decent amount of zooming in before things get blurry, even on retina displays. Your image size will reach a maximum of 5.X MB, which is well below the Apple guidelines. If you want to optimize overall file size, you will need to reduce image size and start downgrading image quality. In Photoshop, your Image Size panel will look just like this:
The only parameters you need to concern yourself with are the Width and Height in pixels. resolution is irrelevant -you are sizing your image in absolute terms (pixels).
For your cover page, you will want to size at 1004 x 768 pixels.
Sharpening: to my surprise, sharpening images for use on iPads (including retina displays) doesn’t appear to make any noticeable difference except at maximum zoom in levels. After many tries, I now skip sharpening altogether. Your results may vary depending on the type of images you are using, but I would advise doing a quick test with and without sharpening before you settle on a final workflow for image treatment.
Image type: while JPEG is the recommended file format, you can save your files as PNG if you need transparency. Note that iBooks Author gives you tools to both modify the opacity of and apply transparency to a JPEG .
Sizing with the Inspector: the metrics tab of the Inspector should be adjusted for proper sizing and positioning. For a full screen, centered image you want to adjust the available parameters as follows:
With our chosen resolution, these settings will allow for a decent amount of zooming in before things get blurry. Your image size will reach a maximum of 4 to 5 MB, which is well below the Apple guidelines. You should also remain under their maximum book size requirements unless you have a very large number of pages with full screen images.
Your cover will have different Inspector settings, as shown below: