Bitmap

A bitmap is a digital image composed of a grid of picture elements, or pixels. Each pixel encodes color information, and the collective arrangement of pixels forms the final picture. Bitmaps are a form of raster graphics, as opposed to vector graphics, which describe images with geometric shapes and mathematical formulas.

In memory or on disk, a bitmap is stored as a two-dimensional array of pixel values. The total size depends on the width, height, and the number of bits used to represent each pixel (the bit depth). Common depths include 1-bit monochrome, 8-bit indexed color, 24-bit true color, and 32-bit color with an alpha channel.

Bitmap formats vary in how they store data and metadata. The Windows Bitmap (BMP) format is a well-known example that includes a header, color information, and pixel data, which may be uncompressed or compressed with simple schemes. Other raster formats such as PNG, GIF, or JPEG also represent pictures as pixel grids, but each has its own encoding and metadata.

Pixel rows are typically arranged line by line, sometimes with padding to align scanlines to word boundaries or specific byte boundaries. Some formats store rows top-down, others bottom-up; the details affect how software reads and writes the image.

Advantages of bitmaps include straightforward access to individual pixels and compatibility with image editing workflows. Disadvantages include large file sizes for high-resolution images and potential scaling artifacts when the image is enlarged without smoothing.

See also: raster graphics, vector graphics, image compression, color depth.