Place a guide in the exact center of two other guides?

[SilverBlade]

I'm new to Gimp, coming from Photoshop.

In Photoshop, you can place a guide in the exact center of two existing guides. How do I do that in gimp?

[Ofnuts]

Short of figuring out their positions and doing the math,I don't know

Guides are on integer positions (they are actually on the boundaries between pixels), you can't have a guide in the exact middle of two other guides that are separated by an odd number of pixels.

If you tell use what you are trying to do, we could come up with ways to achieve it differently.

[SilverBlade]

(08-19-2018, 06:14 AM)Ofnuts Wrote: Short of figuring out their positions and doing the math,I don't know

Guides are on integer positions (they are actually on the boundaries between pixels), you can't have a guide in the exact middle of two other guides that are separated by an odd number of pixels.

If you tell use what you are trying to do, we could come up with ways to achieve it differently.

Basically, making blu-ray covers.

I'd need a guide at each edge of the image, plus two vertical guides in the middle for the spine. One more guide in between those two to more easily center-align/scale images and text on the spine so nothing goes over

And, on the front/back sides of the cover, I'd need a few more guides. One horizontal guide down the middle, and 2 more, vertical, down the middle of both the front and the back sides of the cover. 

Anything off-center looks really bad.

[rich2005]

Scrapped a rather long general post - back to the actual question.

Quote:..In Photoshop, you can place a guide in the exact center of two existing guides. How do I do that in gimp?

No specific tool that I know, maybe someone knows of/will write a script.

For Gimp 2.10 a workaround other than some arithmetic to determine the center.

Use the unified transform tool on the canvas. looks like this https://i.imgur.com/8oHCcg6.jpg
Pull the edges in to snap on the existing guides: https://i.imgur.com/CPAX4iq.jpg
The default center is marked, zoom in, drag in a guide: https://i.imgur.com/rV8qE9S.jpg
Close the tool without using it, ESC or close the on screen dialogue.

if you don't like that tool, same thing but using rectangular selection tool, options for center / thirds ... https://i.imgur.com/tYUHAgf.jpg