05-25-2019, 07:26 PM
A reminder that Gimp works in pixels not centimetres, however
Could do with a little more information - pixel size / ppi of the original image before scaling.
One immediate question. Why use the Unified transform scale rather than Image -> Scale Image which must be a more accurate way.
First thoughts, There are rounding errors - pixels to real-world-units. 30 cm x 50 cm which might be so close as to make no difference but scaled up to "50 x 80" gives an actual 50 x 83.3 which would be that 3 mm.
Have you checked the original for a tiny error that might be magnified by scaling.
If stuck maybe scale oversize by a tiny amount and crop back down to size.
Could do with a little more information - pixel size / ppi of the original image before scaling.
One immediate question. Why use the Unified transform scale rather than Image -> Scale Image which must be a more accurate way.
First thoughts, There are rounding errors - pixels to real-world-units. 30 cm x 50 cm which might be so close as to make no difference but scaled up to "50 x 80" gives an actual 50 x 83.3 which would be that 3 mm.
Have you checked the original for a tiny error that might be magnified by scaling.
If stuck maybe scale oversize by a tiny amount and crop back down to size.