gd is a graphics library. It allows your code to quickly draw images
complete with lines, arcs, text, multiple colors, cut and paste from
other images, and flood fills, and write out the result as a PNG, GIF
or JPEG file. This is particularly useful in World Wide Web applications,
where PNG, GIF and JPEG are three of the formats accepted for inline
images by most browsers.

gd does not provide for every possible desirable graphics operation,
but version 2.0 does include most frequently requested features,
including both truecolor and palette images, resampling (smooth
resizing of truecolor images) and so forth.

WWW: http://www.libgd.org/