Description:

gd is the image manipulating library. It was created to allow graphs,
charts and the like to be generated on the fly for use on the World
wide Web, but is useful for any application in which custom images are
useful. It is not a paint program; it is a library. gd library creates
PNG, JPEG, GIF and WBMP images. PNG is a more compact format, and full
compression is available. JPEG works well with photographic images,
and is still more compatible with the major Web browsers than even PNG
is. WBMP is intended for wireless devices (not regular web browsers).