Why doesn't my Gimp perspective transform apply to the entire image?

Question

I'm trying to correct the perspective of a photo in GIMP, but I can't seem to get it to apply to the entire image. The transformation applies to a small area and leaves empty white space around it.

I start with this image:

When I select the Perspective tool and click anywhere in the canvas, the grid appears, already scaled to just the subject:

I set up my transformation to line up the product label with the guides:

And this is the result:

How can I get GIMP to transform the entire image, and not add that extra white space?

What I've tried so far:

• Extending the grid to cover the entire canvas - this results in stretching the subject
• Changing the Clipping setting - no effect
• Fit Canvas To Layers - no effect
• Removing the guides - no effect

Answer 1

You say:

When I select the Perspective tool and click anywhere in the canvas, the grid appears, already scaled to just the subject

Emphasis added, because that's important. This is not the normal behavior of the perspective tool. Normally, if you just click, the grid will cover the entire image. It sounds like you have your subject pre-selected. You don't describe having done that (and I don't see the "ants" in your screenshots), but perhaps you have "show selection" off (ctrl-t), and previously selected the subject area and forgot it.

The behavior when working with a selection of part of the image is exactly what you describe.