You can resize the canvas of an image/animation using this dialog (menu Frame).
Maintain Aspect Ratio keeps the images width-height proportion.
So you can then only change either width or height.
New Width and New Height define the dimensions the
image is to be scaled to
+ Brush Width and + Brush Height add the brush size to the frame size.
Brush size/Frame size put the corresponding sizes into the edit fields.
Scale image offers different scaling options. The resample options
use bicubic sampling. When using resamling you may enable dithering.
Reposition resizes the project and the nine position buttons may be
used to align the image before it is clipped.
Related topicsMenu Frame