File format or simply a Bitmap is a Raster graphics image file format used to store bitmap digital images, independently of the display device. A file that indicates a color for each pixel along the horizontal axis or row (Called the x coordinate) and a color for each pixel along the vertical axis (called the y coordinate). Bitmap Image. The BMP File Format is capable of storing 2D digital images of arbitrary width, height, and resolution, both monochrome and color, in various color depths.