Changing resolution (DPI)

[carmen]

Hello!
My question: is there some way/plugin to change the resolution (dpi) of an existing XCF image?
My reason: 
1. I never print, but export to .jpg or .png for inclusion on ePub books (XHTML)
2. Conflicting resolutions complicate importing layers/paths from other files
3. Through different oversights on my part (failure to delete in Irfanview the original resolution of an image before opening it in Gimp, difference between Gimp versions, not setting the default resolution in preferences...) my XCF images now range from 72 dpi to ~1200 dpi
3. I  would wish I to set it for all at 96 dpi, but haven't found a way to do this.
Help highly appreciated!
Thanks.

[Ofnuts]

See Image>Print size

[rich2005]

As Ofnuts,
but are you looking to do this in a batch mode maintaining all layers etc.

[carmen]

(11-14-2018, 04:10 PM)rich2005 Wrote: As Ofnuts,
but are you looking to do this in a batch mode maintaining all layers etc.

Right! I do not print--and if I ever did, I know how to set 'Print size'. What I would wish is to be able to go to 
Image-->Image Properties
and be sure to see always 'Resolution 96 x 96 ppi' with my chosen 'Size in pixels'--'Print size' is entirely immaterial to me.
Thanks!

[rich2005]

(11-14-2018, 04:41 PM)carmen Wrote: Right! I do not print--and if I ever did, I know how to set 'Print size'. What I would wish is to be able to go to 
Image-->Image Properties
and be sure to see always 'Resolution 96 x 96 ppi' with my chosen 'Size in pixels'--'Print size' is entirely immaterial to me.

You can set the resolution, image-by-image, as Ofnuts pointed out using Image -> Print Size, it just sets the ppi, otherwise keeps the image as-is. Then you need to Save https://i.imgur.com/x4mEsA1.jpg

I was wondering if you had maybe a few hundred to convert, I do not know of anything so far, can do it with BIMP but seems to lose some layers for some reason.

[carmen]

(11-14-2018, 04:06 PM)Ofnuts Wrote: See Image>Print size

Thanks! That works! I had tried through File-->Print, which definetily doesn't...
 

Quote:rich2005 Wrote: 

I was wondering if you had maybe a few hundred to convert...

Just made a windows search--2000 XCF files reported--not knowing how many can need fixing...
Anyway, I grow increasingly peeved with the inability to share layers/paths/text sizes on the fly, between two images with the same 'Image size', due to those pesky dpi...
Thanks!

[Ferdrimmler]

(11-14-2018, 04:06 PM)Ofnuts Wrote: See Image>Print size

I want to change the DPI.  Just the DPI.  Not the print size.  Is there any simple way to do that?
Image>Print size "changes the DPI" by scaling the print size.
I have 42 pictures that are all different sizes at 1200 dpi, which I need to be 7.75" by 7.75" at 300 dpi.

[Ofnuts]

Print size in inches, size in pixels, and definition in DPI (or more  accurately, PPI) are inter-related, you cannot change just one:

  print size = size in pixels / definition

which is strictly equivalent to:

  size in pixels = print size * definition  

or

  definition = size in pixels / print size

In Image>Print size you can change the print size and the definition, but this won't change the size in pixels, because while print size and definition are just metadata and can be changed at will, changing the size in pixels alters the image data itself in irrevocable ways.

So, if you want your images to be 7.75"x7.75" at 300PPI, they need to be 2325x2325 pixels which may require scaling them.

[rich2005]

In pictures

Not difficult, keep in sequence.

Assuming the images are cropped to square

1. Image -> Scale Image to open the scale dialogue. You can use inches in the drop down menu but keep an eye on the size in pixels shown.

2. Leave width and height alone. Change the X and Y resolutions to 300 ppi The width and height change to suit but the size in pixels remains the same.

those screenshots. https://i.imgur.com/VwcjpS1.jpg

3. Change the Width and Height as required (Not paying attention, I used 7.5 inches). The size in pixels now changes and the ppi remains the same (300) Click the scale button

4. Check you have done it correctly in Image -> Print Size.

more screenshots: https://i.imgur.com/zsFEK51.jpg

I did make a video for someone else, for those who like videos https://youtu.be/VMye0G77lD4