bitmap
n.A raster graphic formed by an array of bits, each bit representing the corresponding pixel's value (light or dark).A raster image formed by an array of bytes, each byte (or bytes) representing the corresponding pixel's color; a pixmap.
Notes
A bitmap1 is necessarily a bitonal image as a bit can represent only two values. - A bitmap2 that represents shades of gray or color requiring more than one bit per pixel is sometimes called a pixmap. In Microsoft Windows conventions, a file name for a bitmap2 has the extension .bmp.