Image::Size is a library based on the image-sizing code in the wwwimagesize
script, a tool that analyzes HTML files and adds HEIGHT and WIDTH tags to
IMG directives. Image::Size has generalized that code to return a raw (X, Y)
pair, and included wrappers to pre-format that output into either HTML or a
set of attribute pairs suitable for the CGI.pm library by Lincoln Stein.
Currently, Image::Size can size images in XPM, XBM, GIF, JPEG and PNG
formats.

I did this because my WWW server generates a lot of documents on demand
rather than keeping them in static files. These documents not only use
directional icons and buttons, but other graphics to annotate and highlight
sections of the text. Without size attributes, browsers cannot render the
text of a page until the image data is loaded and the size known for layout.
This library enables scripts to size their images at run-time and include
that as part of the generated HTML. Or for any other utility that uses and
manipulates graphics. The idea of the basic interface + wrappers is to not
limit the programmer to a certain data format.

WWW: http://search.cpan.org/dist/Image-Size/