You can view image type below gd tag. you can use to print server variables.

If GD library is installed than you can check what type of images that the PHP version supports.

Example:

gd

GD Support enabled
GD Version bundled (2.0.28 compatible)
FreeType Support enabled
FreeType Linkage with freetype
FreeType Version 2.1.9
T1Lib Support enabled
GIF Read Support enabled
GIF Create Support enabled
JPG Support enabled
PNG Support enabled
WBMP Support enabled
XBM Support enabled