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 or JPEG file. This is particularly
useful in World Wide Web applications, where PNG and JPEG are two of the formats
accepted for inline images by most browsers.
gd is not a paint program. If you are looking for a paint program, you are
looking in the wrong place. If you are not a programmer, you are looking in the
wrong place, unless you are installing a required library in order to run an
gd does not provide for every possible desirable graphics operation. It is not
necessary or desirable for gd to become a kitchen-sink graphics package, 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.