Changing template spine size.

[rich2005]

(06-05-2024, 08:08 AM)Stusamuso Wrote: After reviewing one of my indi books, I want to increase the spine width from .835"/21.21mm to 0.880"/22.35mm in my Gimp 2.10.36/Windows11. I am reusing my original book template so the only change required is the spine size (more pages in the new edition). How can I best do this in Gimp? Step by step would be good. 
Secondly when I open a template image as a PNG in Gimp, how can I view its actual size?  Thanx, Stusamuso.

The usual warning. Gimp is a bitmap editor and works in pixels not inches or millimetres. The real-world units come from the resolution of the image.

Is this a KDP template? An example I got from https://kdp.amazon.com/cover-calculator has a resolution of 600 ppi.

First thing to check is the resolution value of your image. Look in Image -> Print Size and it gives the ppi value.

Assuming 600 ppi then (0.88" - 0.835") 0.045" x 600 ppi  = 27 pixels needed to increase the image size.

You can split an image using guides and use one side to nudge along that 27 pixels. 
Step-by-Step (yeah right) see if you can follow this PDF I put on my storage http://u.pc.cd/N5j

View actual size. Turn View -> Dot-for-Dot off . Set Image zoom to 100%

Edit: Ahh. Missed a bit out of that PDF, not doing it again.
You need to add the second guide using Image -> Guides -> New Guide and set a value (first guide position + 27) pix