Requirements

If you have the GD library (available at » http://www.libgd.org/) 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. GIF support is available as of gd-2.0.28.

Note: As of PHP 5.0 libgd-2.0.4 or higher is required. As of PHP 5.5 libgd-2.1.0 or higher is required. Alternatively, use the bundled GD library that ships with PHP.

You may wish to enhance GD to handle more image formats.

Supported image formats
Image format Library to download Notes
gif   Only supported in GD versions newer than gd-2.0.28. Write support is available as of PHP 5.0.1.
jpeg » http://www.ijg.org/ When building the jpeg library (prior to building PHP) you must use the --enable-shared option in the configure step. If you do not, you will receive an error saying libjpeg.(a|so) not found when you get to the configure step of building PHP.
png » http://www.libpng.org/pub/png/libpng.html
xpm » ftp://metalab.unc.edu/pub/Linux/libs/X/!INDEX.html It's likely you have this library already available, if your system has an installed X-Environment.

You may wish to enhance GD to deal with different fonts. The following font libraries are supported:

Supported font libraries
Font library Download Notes
FreeType 1.x » http://www.freetype.org/ Support for FreeType 1.x has been removed as of PHP 5.3.0.
FreeType 2 » http://www.freetype.org/  
T1lib » ftp://sunsite.unc.edu/pub/Linux/libs/graphics/) Support for Postscript Type 1 fonts (Removed as of PHP 7.0.0).