Recently I’ve had the pleasure of publishing Linda Needham’s most recent book through Kindle Direct Pubishing (eBook) and CreateSpace (paperback). Her book is the 20th century historical romance, “The Legend of Nimway Hall: 1940-Josie“.
In the process, I learned a lot about indie publishing (see this site’s Creating eBooks menu for my notes so far) and experimented with how to make a CreateSpace book cover (a professional created Linda’s book cover).
One issue I ran into: I couldn’t reliably create a cover file, using Gimp, that would have the correct size in both inches and pixels. This post explains what I think the issue is; my cover how to page includes my advice on how to work around the issue.
A Little Background & the Issue
CreateSpace is an Amazon company devoted to print-on-demand services for indie publishers. We used CreateSpace to publish the paperback edition of Linda’s book. Gimp is an open source image editor that I used to create paperback cover experiments – Gimp is similar to Adobe Photoshop.
CreateSpace requires that cover art be submitted in PDF format, and be a book-specific size. CreateSpace also has a cover template file generator, that produces .pdf and .png files you can use to create your book cover.
PDF format gives the physical size of a bitmap (in fractional Points, which are 1/72″), the resolution in dots per inch, and the size of the image in pixels. So far, so good.
PNG format gives the size in pixels of a bitmap, and can optionally express the X and Y pixels per meter: the resolution.
Here is the problem I ran into: I could open Gimp, read the template .png file, edit a cover based on that file, and save the cover in PDF format… but the generated file, when imported back into Gimp, would sometimes be 1 pixel narrower than required. And what’s worse, I couldn’t seem to predict, for any given cover, whether that cover’s PDF file would be the right width!
CreateSpace’s Cover Art Requirements
CreateSpace offers a downloadable PDF Submission Specification, whose Cover Specification section gives detailed requirements for your book cover PDF file. Their Setup / Cover upload page gives additional requirements. The cover size related requirements are:
- The cover art must be as wide as the front cover + your book’s spine + the back cover + a specified bleed width. Note that this means that the cover width depends on the number of pages in the book. For example, the spine of a 100 page book will be narrower than one for a 400 page book.
- The examples imply that the cover dimensions are rounded to 0.001 inches.
- The cover image must have a minimum resolution of 300 dots per inch.
- The cover image file to upload must have a maximum file size of 40 MB.
An example 260-page book
Suppose for example that your book is 260 pages, printed in monochrome (black & white) on white pages with a Trim Size (finished book size) of 5.5″ x 8.5″. Feeding those choices into CreateSpace’s cover template file generator produces a PDF file (which we’ll ignore) and a .png file that has the following properties:
- 3551 pixels wide
- 2625 pixels high
- x and y resolution of 300.000 pixels per inch.
CreateSpace gives formulas for calculating the physical cover dimensions in the Calculating the Cover Size section of their PDF Submission Specification (linked above), which gives the following information relevant to our example:
- For Black & White books with White paper, multiply the page count by 0.002252” to calculate the spine width.
- Cover Width = 0.125″ Bleed + Back Cover Width + Spine Width + Front Cover Width + 0.125″ Bleed
- Cover Height = 0.125″ Bleed + Trim Height + 0.125″ Bleed
That calculation gives a cover physical size of:
- Cover Width = 11.836″ (0.125″ + 5.5″ + (260 * 0.002252″) + 5.5″ + 0.125″, rounded to 0.001″ resolution)
- Cover Height = 8.750″ (0.125″ + 8.5″ + 0.125″, similarly rounded)
At 300 pixels per inch, rounded to the nearest pixels, that’s
- Cover Width = 3551 pixels
- Cover Height = 2625 pixels
Notice that because the width was rounded and the height wasn’t, the horizontal and vertical resolution are different:
- X Resolution = 300.1689 pixels/inch (3551 / 11.836″)
- Y Resolution = 300.000 pixels/inch (2625 / 8.750″)
“…it’s going to be bad for the pitcher”
In the play “Man of La Mancha”, Sancho Panza, Don Quixote’s side-kick, says “Whether the stone hits the pitcher or the pitcher hits the stone, it’s going to be bad for the pitcher.” We have a similar situation here: whether we calculate pixels from inches or inches from pixels, it’s going to be bad for the picture.
The problem, I believe, is that Gimp – appropriately – tries to enforce the relationship that the physical dimensions of the image = the pixel dimensions divided by the resolution, but because the number of pixels has been rounded, that relationship isn’t exact. That is:
- 3551 pixels / 300 pixels per inch = 11.83666…”, not 11.836″
- Luckily, 2625 pixels / 300 pixels per inch = 8.750″ exactly.
Gimp’s Print Size dialog seems to enforce the relationship between the physical size of the image, its dimensions in pixels, and its resolution. For example:
- If you type a new physical width, the resolution value changes so that width * resolution = the image width in pixels.
- If you type a new physical height, the resolution value similarly changes.
- If, on the other hand, you type a new resolution, the physical dimensions change so that, again, width * resolution = the image width in pixels, and similarly the height * resolution = the image height in pixels.
Further, it seems that – at least for Gimp version 2.8.22 – when I even click on one of the fields in the Print Size or Scale Image dialogs, Gimp recalculates the other fields as if I’d changed the field I clicked on.
A cool tool, TweakPNG, reports the following metadata for the CreateSpace template .png file:
- Width: 3551 pixels
- Height: 2625 pixels
- Pixel size: 11811 x 11811 pixels per meter (300.0 pixels per inch)
All this would be a bit academic, except that CreateSpace requires a PDF-format cover; not a .png format cover. So the image size can be distorted a little in the translation between .png and .pdf, losing a pixel of width.
The upshot of all this is that I believe that to make sure that your Gimp-created PDF file is the correct size for your CreateSpace book, you should:
- Start from the CreateSpace-generated template .png file, which (I believe) has the correct, though inconsistent, size in pixels and resolution. That is, don’t create a Gimp cover image from scratch, and don’t start from the PDF template.
- Never click OK in the Print Size, Canvas Size, or Scale Image dialogs, because doing so will change either the physical dimensions or resolution in the exported PDF.
My page on Creating Your CreateSpace Cover Using Gimp incorporates what I’ve learned into a set of step-by-step instructions for a (hopefully) successful cover-creation experience.