This isn't a very exciting post, but it took me ages to figure it out, so I wanted to write it down somewhere.

I wanted to use a one line ImageMagick command to:

Take four pictures

Resize, centre and crop them to be square thumbnails

Arrange them in a 2 by 2 grid

Here is the command for ImageMagick on Windows:

convert -size 300x300 xc:transparent

-page 150x150 ( "image1.jpg" -gravity center -resize 150x150^^ -extent 150x150 )

-page 150x150 ( "image2.jpg" -gravity center -resize 150x150^^ -extent 150x150 -repage +0+150 )

-page 150x150 ( "image3.jpg" -gravity center -resize 150x150^^ - …