While XPM is a common enough image format, sometimes you want to work
with industry standards, such as JPEG, PNG, or GIF (if you can't stop
yourself). Welcome to gdk-pixbuf.
gdk-pixbuf is a library for image loading and manipulation. It supports
BMP, GIF, ICO, JPEG, PNG, PNM, RAS, TIFF, and XBM/XPM image formats,
can render images to drawables, scale and composite images against
various backgrounds, create pixmaps/masks out of images, and so on.
PHP-GTK provides interface to some of the more common functions of the
gdk-pixbuf library. Unfortunately, gdk-pixbuf support is not yet
available on Windows platforms.
gdk-pixbuf extension defines a GdkPixbuf class which is used to represent an
in-memory image data. All operations on the image are carried out by invoking
methods of that class.