Move a selectionbox to the center of a layer and copy

[iamzesh]

Hello,

after searching a lot I cannot find a way to move a selection and to use it to copy a part of a layer.
So to be clear,
I have a layer, 1024x768, with a picture
I want to select a portion of it (eg a rectangle of 200x300), from its center and use it
I thought I could do the following, use the select tool, create a 200x300 selection, align it on the center of layer with the align tool, then Ctrl+C, create a new document, 200x300, Ctrl+V and job done!

But I cannot find a way to move my 200x300 box (because the align tool never selects my 200x300 rectangle but the whole layer) and then to use it to "capture" the center of the layer. I tried to use select > float on the same layer or on the other but it doesn't work.
Does anyone could help me with this?

[Arzoroc]

The alignment tool has not got the option of aligning a selection at the moment. There are different ways to recieve your desired result though:
1) You use your technique, paste your new 200x300 layer into the SAME Gimp project (as a new layer instead of a whole new image), then use the align tool to align the layer to the center of the image, and then use the Alpha to selection function (rightclick on the new layer in the layers dialog, > Alpha to Selection) to select the "outline" of your new layer, which is exactly in the middle of your image.
2) You select the rectangular selection tool, go to the tool options (If you can't find them, click on "Windows > Dockable dialogs > Tool options) and write the exact width/lenght of your selection (200x300) and the desired location. This requires you to know the dimensions of your image and calculate a little (Take the middle point pixel coordinates and go -100 in the one direction and -150 in the other).

There are probably some other ways (maybe also easier ones) but I'm too tired to think properly atm I hope I could help.

[iamzesh]

Thank you very much, Arzoroc!
It worked just fine!
I have a preference for the first method as it lets the computer do the job for centering instead of me calculating widths, heights and so on: much quicker and less prone to error!