Blitting

Blitting, short for bit-block transfer, is a computer graphics operation that copies rectangular blocks of pixel data from a source bitmap to a destination surface. The operation is fundamental in raster-based graphics systems and underpins sprite rendering, scrolling, GUI compositing, and double-buffered frame updates. A blit typically specifies a source rectangle, a destination position, and optionally a set of pixel operations such as simple copy, transparency (color key), or alpha blending. More advanced variants support stretching (scaling), masking, and partial updates.

Historically, blitting was implemented in both software and hardware; early systems used CPU-driven copies, while modern systems rely on graphics processors or dedicated blitters that can move data at high bandwidth and perform blending in parallel. In many APIs and frameworks, the term blit is used to describe operations that transfer image data between surfaces or textures, sometimes with alpha compositing or color-key transparency.

Common use cases include rendering sprites from a sprite sheet to the screen, scrolling a background by copying parts of a larger image, and compositing UI elements over a scene. Performance considerations focus on memory bandwidth and cache locality; developers arrange surfaces to minimize cache misses and use double buffering to avoid tearing. Hardware blitters and GPU-accelerated copy and blend operations have largely replaced CPU-based blitting in modern systems, enabling higher rates of update and more complex effects.