Crop with Fixed Aspect Ratio

[jakthelad]

Unless I am mistaken there is no facility for this :-

Suppose I have an image from which I wish to extract a portion for printing.
I wish to print it on say standard 100 x 150 portrait print paper, either with no margin or with a small equal margin all round.
I want to open a crop box with the precise aspect ratio to suit the paper, and then adjust the size of the crop box (whilst preserving that aspect ratio) to take in precisely as much of the image as I wish to select.

A similar facility would be useful for the aspect ratios of other standard photo print paper sizes, in both portrait and landscape views.

If such exists or can be easily constructed, would someone kindly point me in the right direction. Thanks.

[Bhikkhu Pesala]

Create Custom Selection (Shift C). select a preset ratio or type any one you want. Control + drag the selection in the viewer to retain the aspect ratio. Right-click to move it. Control Y to crop.

[jakthelad]

Thanks so much. Clearly I had overlooked it.

[Laurent]

Hi jakthelad,

Keep in mind that the aspect ratio for your selection isn't the same as the aspect ratio of your paper. The difference is small if margins are thin.
For example for a 100 mm x 150 mm paper the ratio is 1.5, but with margins 5 mm thick the image is 90 mm x 140 mm and its ratio is 1.556.

Laurent