How to resize images to either 900-pixels-height for vertical ones or 900-pixels-width for horizontal ones?

Question

I have vertical (i.e. height > width) and horizontal (i.e. width > height) images. I want to resize them to either 900-pixels-height vertical ones or 900-pixels-width ones based on their original ratio.

I am using Ubuntu 20.04 in Gnome environment. I think that mogrify of imagemagick will solve this problem, a pseudo code would be like...

for i in *.jpg; do
  _w = identify -format %w
  _h = identify -format %h
  
  if [_w >= _h]; then
    mogrify -resize 900x675 i
  else
    mogrify -resize 675x900 i
  fi    
done

but couldn't find the way.

Answer 1

This should be enough:

mogrify -resize 900x900\> *.jpg

From https://legacy.imagemagick.org/Usage/resize/#noaspect

Aspect ratio is preserved basically so that any circles in the input image will remain a circle in the output image. That is the image will not be squashed or squeezed, only resized, unless you tell it otherwise.

and

Only Shrink Larger Images ('>' flag) Another commonly used option is to restrict IM so that it will only shrink images to fit into the size given. Never enlarge.