N.B. This driver is disabled by default because it is not maintained and because it depends on the deprecated plfreetype approach (see the section called “Adding FreeType Library Support to Bitmap Drivers”) for rendering unicode text (which implies font-selection issues and no support for complex text layout).
The gd driver uses the GD library to produce plots in the PNG, JPEG, and GIF file formats. Text is anti-aliased, but lines and fills are not.
The available driver options are:
optimize: Optimize PNG palette when possible
def_black15: Define idx 15 as black. If the background is "whiteish" (from "-bg" option), force index 15 (traditionally white) to be "black"
swp_red15: Swap index 1 (usually red) and 1 (usually white); always done after "black15"; quite useful for quick changes to web pages
8bit: Palette (8 bit) mode
24bit: Truecolor (24 bit) mode
text: Use driver text (FreeType)
smooth: Turn text smoothing on (1) or off (0)