<graphics, file format> A data file or structure which corresponds bit for bit with an image displayed on a screen, probably in the same format as it would be stored in the display's video memory or maybe as a {device independent bitmap}. A bitmap is characterised by the width and height of the image in pixels and the number of bits per pixel which determines the number of shades of grey or colours it can represent. A bitmap representing a coloured image (a "pixmap") will usually have pixels with between one and eight bits for each of the red, green, and blue components, though other colour encodings are also used. The green component sometimes has more bits that the other two to cater for the human eye's greater discrimination in this component. See also vector graphics, image formats. (1996-09-21)

In computing, a bitmap is a mapping from some domain (for example, a range of integers) to bits. It is also called a bit array or bitmap index.

(Contraction of "pixel map"). A 3 dimensional array of bits corresponding to a 2 dimensional array of pixels. It is used, for example, in the X Window System to describe a memory region where graphics can be drawn without affecting the screen. Typically this is used for the efficient handling of expose events, icon images or for animation. Compare bitmap. [Xlib Guide].

<graphics, file format> (DIB) An image format in which the sequence and depth of pixels in the file is not specifically related to their layout in any particular device. This allows any device dependent bitmap (DDB) image to be converted to or DIB format without loss of information, and this can then later be converted to other DDB formats for, e.g., printing or display. Rather than requiring converters from each DDB format to all other formats, only converters to and from DIB are needed. DIB images are normally transferred in metafiles, bmp files, and the clipboard. Transferring colour bitmaps from one device to another was not possible in versions of Microsoft Windows earlier than 3.0. Application programs can build DIB images without any interaction with Windows. If Windows lacks a drawing primitive, the application can simulate it directly into the DIB instead of using the existing graphics device interface (GDI) primitives. Unfortunately, under Windows versions 3.0 and 3.1, GDI cannot perform output operations directly to a DIB. Conversion between DIB and DDB is performed by the {device driver}. Where the driver does not have this facility, the conversion is performed by GDI but only in monochrome. DIBs are slower to use than device dependent bitmaps due to the conversions required. (1996-09-20)

bitmap display

In computer graphics, the X Window System used X BitMap (XBM), a plain text binary image format, for storing cursor and icon bitmaps used in the X GUI. The XBM format is superseded by XPM, which first appeared for X11 in 1989.

The Glyph Bitmap Distribution Format (BDF) by Adobe is a file format for storing bitmap fonts. The content takes the form of a text file intended to be human- and computer-readable.

<graphics, file format> (WBMP) A bitmap for display on a WAP mobile phone. Currently (2001) the only type of WBMP file defined is a simple black-and-white image file with one bit per pixel and no compression. [WAP Forum (http://wapforum.org/), "WAP-190-WAE-Spec" or "Wireless Application Protocol, Wireless Application Environment Specification"]. (2001-05-23)

smiley face] in the top left corner is a raster image. When enlarged, individual pixels appear as squares.