Controller driver and display panel driving method

A controller driver includes a driving process circuit configured to receive background bit map data of a background image and font data for a character image, and a font drawing circuit configured to generate pixel data of the character image from the font data. The font data for a pixel is described in a format in which a bit length of the font data for the pixel shorter than in a RGB format, and the driving processing circuit displays on a display panel a synthetic image in which the character image is superimposed on the background image in an on-screen display mode, by driving the display panel based on the background bit map data and the pixel data of the character image.