Size change error

[jediguitar101@yahoo.com]

I'm using 2.10.14...and when I switch from pixels to inches...the scale is WAY off.  (1665 px to 23+" ?!) I'm figuring it's the dpi the image is in...can I adjust the dpi of a copied image? If I rescale it...will it essentially do this...or would it keep the same dpi?

[rich2005]

(01-16-2021, 04:10 PM)jediguitar101@yahoo.com Wrote: I'm using 2.10.14...and when I switch from pixels to inches...the scale is WAY off.  (1665 px to 23+" ?!) I'm figuring it's the dpi the image is in...can I adjust the dpi of a copied image? If I rescale it...will it essentially do this...or would it keep the same dpi?

The error is in the way you expect things to work.
Gimp is a bitmap (raster) editor and works only in pixels. The image size in pixels is shown top of the image window (and in the image properties)

Changing the units from pixels to inches / centimetres / yards / miles does not change the image size in pixels.

   

Scaling an image ( here x2) is also a pixel operation, the pixels size is x2. An added operation might change the stored print size but not the pixel size. This comparison scaled x2 and also changed print size from 72 pixels-per-inch (ppi) to 300 ppi. The display is changed, rulers display the adjusted size but the only thing that counts is the image size in pixels. 

   

Check out Ofnuts discourse on printing resolutions.  https://www.gimp-forum.net/Thread-Image-size-in-Gimp

[jediguitar101@yahoo.com]

@rich2005...thank you very much for the clarity!

So, am I correct in thinking that no matter what I do the "resolution" will always remain the same. And when I'm pulling in an image and then switching to "inches"...the size is being affected by whatever my default "print resolution...ppi" happens to be set at?

[rich2005]

That is it. The units displayed is only an internal Gimp calculation pixels-to-inches / pixels-to-millimetre and so on. The image in Gimp is W pix x H pixels. All to do with when an image gets sent to a printer

A 400 x 800 pix image with a ppi of 100 prints 4" x 8"
Scale that x3 to 1200 x 2400 pix and it still has a ppi of 100 and will print (@100 ppi) 12" x 24"

The place to change the ppi setting is Image -> Print Size which keeps the image size in pixels and changes the image information sent to the printer.
That scaled up 1200 x 2400 pix image with a 200 ppi setting prints 6" x 12"

Of course, once the image is out of Gimp as a jpg / png / etc for printing, print size (from ppi) can be changed by the printer software but the basic pixel information remains which has a bearing on print quality.

[Ofnuts]

https://www.gimp-forum.net/Thread-Image-size-in-Gimp

[rich2005]

I do believe I already mentioned that