[magick-users] resize an image in centimeters?

[Fred Weinhaus]

Just set the density. You have to compute/convert dpi (dots or pixels 
per inch) to dpc (dots or pixels to cm).

See http://www.imagemagick.org/script/command-line-options.php#density



>   hi everybody,
>   I simply need to reduce the length of a very big image; I'm requesting to
>a Geographic map service a 1440x720 pixel image so that, when user reduces
>the image to a 7,5x3,75 cm (that's more or less 3x1,5 inches) in GIMP or
>OpenOffice... it gets about 480 dpi images (for printing).
>  I want avoid the user this final step (resizing for including to a
>document) and directly serve a 7x3,5 cm image.
>
>   I see that resizing is only useful with pixels... how can I get it? (I
>need to request the image with these size in pixels).
>   thanks!
>
>   Pere