Sorry, just a Linux explanation for others who might be interested

I use the following two:
mogrify -resize "x1200" *.jpg
mogrify -resize 1600x -resize "x1200<"

The first makes a picture WhateverX1200. The width can be more or less,
but the hight is 1200.
The second makes it minimal 1600x1200. This means that no matter what,
the with is at least 1600, while the hight is at least 1200.

Say I have a picture that is 600x800. The first will make it 900x1200
The seocnd will make it 1600x2133

If I have a 1200x600 picture, it will become 2400x1200 with the first
and the same with the second.

-==- ROTATE ---------------
mogrify -rotate '90<' penguin.jpeg
mogrify -rotate '90' penguin.jpeg