Crop tool allow growing

[kiwichick]

Hi everyone, excuse the newbie question and apologies if it's been asked before. Can someone please explain to me how the fill option works with crop allow growing? I thought it was going to be a kind of alternative way to resize a canvas but I'm sure I'm misunderstanding something. This is what I'm doing:

1. open an image
2. activate the crop tool
3. check allow growing
4. choose a fill for the extra canvas
5. make a selection that goes outside the image boundary
6. press enter

But, no matter what fill I choose, the extra canvas is always transparent. The GIMP docs aren't really any help but they do say "Transparency will be used if there is no material to crop". If that's the case then what is the fill for? I assumed "no material to crop" was the extra canvas and that's what gets filled.

[PixLab]

Crop Allow growing does not resize the layer, it only resize the canvas
Thus after Allow growing crop-resize, you need to do a right click in the layer stack on the layer you want to use and select Layer to Image size, then you can fill
(or you can select your layer in the layer stack and go to the menu Layer ➤ Layer to image size)

[rich2005]

Not an often asked question. You need the crop tool, but allow growing is a bit of a mess. Two instances.

1. For the whole image. The canvas size is increased. Check the size shown top of the image window but layer size(s) remain as original, so there is nothing to fill with a pattern. You can export that as a png (with transparency) or a jpeg (without transparency) with the new canvas size.
Add a new layer at the bottom of the layer stack and fill with a pattern if that is your desire.

2. On a per layer basis. Check the "current layer only" option. That fills the resized layer with the pattern. The canvas size is not increased. Use View -> View All to see what is there. In this case use `Image -> Fit canvas to layers to correct.

examples: https://i.imgur.com/H4KJXbX.mp4

For a personal preference, I very-very rarely use the crop allow-growing option. Best use Image -> Canvas size.

[kiwichick]

Thanks PixLab and rich2005, it's much clearer to me now :-D