You can use the image functions in PHP to get the size of JPEG, GIF, PNG, SWF, TIFF and JPEG2000 images.
If you have the GD library (available at http://www.boutell.com/gd/) you will also be able to create and manipulate images.
The format of images you are able to manipulate depend on the version of GD you install, and any other libraries GD might need to access those image formats. Versions of GD older than gd-1.6 support gif format images, and do not support png, where versions greater than gd-1.6 support png, not gif.
If you have PHP compiled with --enable-exif you are able to work with information stored in headers of JPEG and TIFF images. These functions do not require the GD library.
In order to read and write images in jpeg format, you will need to obtain and install jpeg-6b (available at ftp://ftp.uu.net/graphics/jpeg/), and then recompile GD to make use of jpeg-6b. You will also have to compile PHP with --with-jpeg-dir=/path/to/jpeg-6b.
To add support for Type 1 fonts, you can install t1lib (available at ftp://sunsite.unc.edu/pub/Linux/libs/graphics/), and then add --with-t1lib[=dir].
This extension does not define any configuration directives.
This extension does not define any resource types.
These constants are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.