Paperclip(ImageMagic) resize, crop and other action sheet cheat

gistfile1.txt

'400x300'            # resize, maintain aspect ratio
'400x300!'           # force resize, don't maintain aspect ratio
'400x'               # resize width, maintain aspect ratio
'x300'               # resize height, maintain aspect ratio
'400x300>'           # resize only if the image is larger than this
'400x300<'           # resize only if the image is smaller than this
'50x50%'             # resize width and height to 50%
'400x300^'           # resize width, height to minimum 400,300, maintain aspect ratio
'2000@'              # resize so max area in pixels is 2000
'400x300#'           # resize, crop if necessary to maintain aspect ratio (centre gravity)
'400x300#ne'         # as above, north-east gravity
'400x300se'          # crop, with south-east gravity
'400x300+50+100'     # crop from the point 50,100 with width, height 400,300