This project explains how to overwrite bytes in the CGRAM to display custom bit-map graphics on a Hitachi HD44780-compatible character LCD display. A method is described of transforming a raster image to an array of values that are a monochrome bit-map representation of the original.
There are many types of LCD displays available on the market. The least expensive and most prevalent is the NxM character display (N=number of lines, M=number of characters per line). The majority of these displays use a Hitachi HD44780 (or compatible) chip. This chip provides a common interface to print characters, move the cursor, shift the display and, most importantly for this discussion, create custom characters on the display.
Displaying A Small Monochrome Picture On A Character LCD: [Link]