So I want to create one large image of size 3600x2280 composed of three smaller images. The first should be resized to 1680x1050 and placed in the top left corner. The 2nd needs to be reiszed to 1920x1200 and placed immediately to the right of it (+1680 over). The 3rd image should be resized to 1920x1080 and placed on the bottom right (+1680+1200). The bottom left will just be blank/transparent.
I've tried various commands I've searched for online and think I'm getting somewhat close with something like the following for just two of the three images:
convert -define png:size=3600x2280 \( Photos/DSC05525-original.jpg -resize 1680x1050 \) -geometry +0+0 -composite \( Photos/Sydney-Loftus-Train-Station-original.jpg -resize 1920x1200 \) -geometry +1680+0 -extent 3600x2280 test.png
...but that places the 2nd image over the first (I think because it doesn't know to extend until the very end?). I've tried various combinations of -composite, -gravity and +repage, but can't seem to find a solution.