On an occasion I experience problem while resampling images. It looks like the "keep aspect ratio" function properly calculates height for typed-in width, but then it does not use this width and it recalculates it again from height.
Example:
- image is 583x132
- I force width to 500px
- RIOT calculates new height as 113px
- final resolution is 499x113...
The only fix for this is to disable "keep aspect ratio" just before clicking ok.
Suggestion: Dialog box should remember which value was typed-in (not calculated) and do not touch it.