Gimp Automatically Resizes

[Immortality]

Hello everyone,

I need to create a cover for my book.

I set canvas width to 10.4325 inches, but Gimp automatically resizes it to 10.433 inches.

How can I stop this from happening?

One thing I notice is that when I frist insert the size: 10.4325 inches, then accept these values.
Next, I open canvas size again, it is not set to inches but automatically displays the values as pixels. When I then click inches again, I get 10.433 inches. 
Is this thus some type of calculation problem taking place?

Thank you,

Immortality

Gimp version: 2.10.24
On: Windows 10 32-Bits

[programmer_ceds]

(07-03-2021, 02:45 PM)Immortality Wrote: Hello everyone,

I need to create a cover for my book.

I set canvas width to 10.4325 inches, but Gimp automatically resizes it to 10.433 inches.

How can I stop this from happening?

One thing I notice is that when I frist insert the size: 10.4325 inches, then accept these values.
Next, I open canvas size again, it is not set to inches but automatically displays the values as pixels. When I then click inches again, I get 10.433 inches. 
Is this thus some type of calculation problem taking place?

Thank you,

Immortality

Gimp version: 2.10.24
On: Windows 10 32-Bits

What you are seeing is presumably the result of arithmetic rounding. As GIMP works in pixels why don't you tackle the problem slightly differently. Decide how many pixels per inch (300?) you want for the printing and then multiply the width and height of your book cover in inches by this value and create an image of this size in GIMP. The size in inches or mm that GIMP shows for the image is irrelevant - assuming that you are not going to print from within GIMP (which is, perhaps, not the best program to print with). You may need to set the number of pixels per inch in GIMP if your printing program doesn't allow you to import an image and then specify the print size. For example you can insert an image into a LibreOffice Writer document and specify the size at which it should be printed regardless of the number of pixels or pixels per inch information stored in the image file (not that I am suggesting using Writer to print)

[rich2005]

Gimp is a raster / bitmap editor where the image is made up from rectangular pixels. You can enter size units such as inches but there is an internal conversion to pixels.
There is also a print resolution, pixels-per-inch (ppi) to consider see: https://www.gimp-forum.net/Thread-Image-size-in-Gimp This is the most important setting for publishing. What are you using ?

Not all inch sizes can be can be converted exactly, especially 4 decimal points. Gimp only displays 3.

Depending on the resolution you initially used you might get this @ 300 ppi for 10.4325"
3129 pixels = 10.430"
3130 pixels = 10.433"
3131 pixels = 10.437"
So, 10.433 is the best you will get and the difference represents part of a pixel (a bit like splitting the atom) It is a negligible. 0.03 %

[Immortality]

Dear Rich and programmer_ceds,

Thank you so much for your quick and insightful reactions.
I self-publish through Amazon's self-publishing platform called "Kindle Direct Publishing", so I just need to bow to the formats they provide. In this case this is 10.4325" x 8.25".
This means I'm not actually myself printing anything, with Gimp interacting with some printing device. I also have no knowledge on the subject whatsoever. If I understand correctly I would need to know the resolution Amazon KDP prints in. I'll have a look, but the process seems a bit prohibitting.

I confess from my user-end point of view, this is very difficult :-). I'm no fool, but I see I have too little experience or development technology-wise to be easily able to work with this.

I will keep trying and see how far I can get with the pointers you have given me.

Thank you so much,

Immortality

[rich2005]

Just out of interest, where does the 10.4325" value come from ? The page sizes are generally x.xx" (2 dp) add on a bleed margin 0.125 and you might get 3 dp x.xxx" but 4 ? is strange. something like this https://kdp.amazon.com/en_US/help/topic/...#covercalc

Gimp might not be the best tool for this either, Bitmap graphics ok, but any text on top is best done with a DTP program such as Scribus. The same applies if Amazon are looking for a PDF, use Scribus.

[Immortality]

Hello Rich,

The value I displayed here comes from KDP's paperback calculator.
Thank you for the reference to Scribus. I'll get there :-).

Immortality

[rich2005]

In case any one else comes to this thread. Lets keep this in perspective.

From the Kindle Direct Publishing calculator ( a spreadsheet) those odd dimension come from the book spine dimensions. Otherwise very much standard 0.125" bleed margin and a 0.125" trim margin.  So there is a 1/8" bleed margin to play with.

   


If the Gimp image needs to be 10.4325" wide (margins+front cover + spine + back cover + margins) at 300 ppi the image should be 3129.75 pixels wide. Gimp works in whole pixel so you get 3130 pixels wide. That is a difference of a 1/4 pixel which at 300 pixels per inch = 1/ 1200" easily lost in the bleed margin.

Not a lot of choice in supported formats HTML, MOBI, RTF, Plain Text, PDF So it looks like Scribus PDF is the best option. Scribus does use 4 decimal points Frame based so there is a learning curve. I would do artwork in Gimp, Title text (especially if some fancy font is used) as a Inkscape vector, other text can be LibreOffice otd. If Kindle wants a CMYK PDF Scribus can do that as well. Plenty of documentation on-line.