It would be nice if the Crop tool had an option that fixes the aspect 
ratio of the rectangle used in cropping. When I crop my pictures for 4x6, 
5x7, 8x10, etc... printings I want a fixed aspect ratio. As for now, I 
have to calculate by hand what is the corresponding height for a 
particular width (and vice versa). And if I change the size of the 
rectangle, I have to recalculate again. That's pretty annoying.

Moreover, that feature would be really easy to implement (it has been 
implemented in the rectangle selection tool). At the interface level it 
could look like this:

Origin  X: 0
        Y: 0

    Width: 1052  (1050.00) 
   Height: 1473  (1472.80)

[x] Use fixed aspect ratio
    X: 5.0
    Y: 7.0

Thanks.

AB