How to resize all images in a directory:

root@linux:~# for i in `ls *.jpg`; do convert -resize 1280x960 $i $i; done

How to convert all bmp images to jpg:

root@linux:~# for i in $(ls); do convert $i `basename $i .bmp`.jpg; done

How to combine 3 images to one in horizontal (use [i+append[/i] for vertical):

root@linux:~# convert -append 1.jpg 2.jpg 3.jpg 1-2-3.jpg

How to create animated gif from static images (-delay is the framerate):

root@linux:~# convert -delay 4 *.JPG output.gif

How to resize an image to width of 200, but keeping the same aspect ratio:

root@linux:~# convert source.jpg -resize 200x target.jpg

How to resize an image to height of 200, but keeping the same aspect ratio:

root@linux:~# convert source.jpg -resize x200 target.jpg