bitmapencodering

Bitmap encoding refers to the representation of raster images as bitmaps, that is, as a two‑dimensional grid of pixels where each pixel encodes color and, optionally, transparency. The term is used across contexts from in‑memory image representations to stored file formats. In practice, bitmap encoding determines how color information is organized (color depth), how rows are arranged, and how the data is stored or transmitted.

Pixel formats vary by color depth. Common options include 1 bit per pixel for monochrome images, 8 bits per pixel with a color palette (indexed color), 16 or 24 bits per pixel for high color, and 32 bits per pixel when an alpha channel is present for transparency. The choice affects memory usage and image quality, as well as how easily the bitmap can be scaled or edited.

In file formats, a bitmap typically consists of a header with metadata (dimensions, color depth, compression) followed by the pixel array. The pixel data may be stored top‑down or bottom‑up, and rows are often padded to align to 4-byte boundaries. Some bitmap formats support simple lossless compression, such as run‑length encoding, while others store uncompressed data.

Encoding and compression strategies vary. Uncompressed bitmaps are straightforward to decode but can be large. Lossless compression formats like PNG (DEFLATE) or GIF (LZW) preserve pixel values, whereas other image types (e.g., JPEG) use lossy methods that do not represent raw bitmaps directly. Bitmap encoding is also central to iconography, bitmap fonts, and textures in graphics pipelines.

See also: bitmap image, raster graphics, image encoding, color depth, run-length encoding.