P3D Re: How to query image dimensions programmatically?

["Greg Wageman" <gjw@xxxxxxxxxx>]

From: marble <marble@xxxxxxxxxxx>


>    is there some way to query an image file to find out its
dimensions?
>if i knew its real height & width, i could get a ratio, and then derive
the
>new width based on my constant height.


If you have access to the "pnm" package (Portable Pixmap/Portable
Greymap/Portable Anymap), you can use the "pnmfile" utility to get back
such information about most common image formats by piping the output of
the appropriate converter.  E.g. on a Unix box,

    giftopnm image.gif | pnmfile

would return the dimensions and bit depth of the resulting anymap.  If
you are using Perl to write your cgi scripts, it would be a piece of
cake to parse the output and capture the dimension information.

Alternatively, the Independent JPEG Group's (IJG) "djpeg" utility could
be hacked to produce a program to give you this information for a JPEG,
and the PNM package's GIF reader could be hacked for GIF images, etc.

The PNM package has been ported to many different operating systems
besides Unix.

     -Greg W. (gjw@xxxxxxxxxx)



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