bitmaps

A bitmap, in computing, is a data structure that represents a spatially mapped array of bits or colors. The term is used for both the in-memory representation of a raster image and for files that store such images. Bitmaps are widely used to describe pixel-based images on screens, printers, and in stored images.

In a bitmap image, each pixel stores color information. The amount of data per pixel is called color depth. Common depths include 1-bit (monochrome), 8-bit (indexed color), 24-bit (true color), and 32-bit (true color with alpha). The image is typically stored as a two-dimensional array of pixels, with scanlines sometimes padded to align to memory boundaries.

Bitmap file formats include the BMP format and various container formats. In raster graphics, some formats compress data (such as PNG lossless, or JPEG lossy). BMP files can be uncompressed or use simple compression and are known for straightforward decoding.

Bitmap also refers to bitmap fonts, where each character is represented by a fixed-size grid of bits; such fonts were common in early graphical user interfaces and embedded systems. Bitmaps can be scaled poorly; when enlarged, they may appear blocky unless anti-aliasing or higher resolution bitmaps are used.

Compared with vector graphics, bitmaps encode images as a fixed grid of pixels, which can lead to large file sizes for high resolution images and make scaling problematic. They are nevertheless fundamental to digital imaging and are the default representation for most photographic images on the web and on devices.