Bpp

Bits per pixel (bpp) is a unit of measurement used in digital imaging to indicate how many binary bits are used to represent a single pixel in an image or video frame. It provides a compact way to describe color depth and data precision.

The bpp value is calculated by dividing the total number of bits required to store the image data by the number of pixels in the image. In uncompressed form, bpp corresponds to color depth: 1 bpp for monochrome images, 8 bpp for grayscale or indexed color, 16 bpp for high color (often used as 5-6-5 RGB), 24 bpp for true color with eight bits per color channel, and 32 bpp for true color with an eight-bit alpha channel (RGBA). Some systems use other 16 bpp representations as well.

Bpp is used to estimate memory usage and data rate. Memory usage for an image in memory is width × height × bpp / 8 bytes. In video, bpp can describe the amount of data per pixel per frame. After decompression, images typically have a defined bpp, but compressed formats can store data more efficiently with palettes, quantization, or other encoding tricks that reduce the effective bits per pixel.

It is important to note that bpp is not a direct measure of visual quality. Two images with the same bpp can look quite different depending on color distribution, gamma handling, and dithering. Bpp is a practical metric for comparing storage and bandwidth requirements across images and formats.

Other uses of the acronym exist in different fields, such as a complexity class in theoretical computer science, but this article focuses on bits per pixel in imaging.