Bitbl

Bitbl, short for bit-block transfer, is a low-level graphics primitive used to move rectangular blocks of pixels from one image buffer to another. In practice, it is implemented as a bitblt operation, sometimes with a raster-operation (ROP) code that defines how source and destination pixels are combined, and may support features such as alpha blending, masking, and clipping. Bitblt is fundamental in GUI compositing, image manipulation, and 2D game graphics, enabling efficient copying, scrolling, and sprite rendering.

The term and concept originated with early bitmap graphics systems and have since evolved across platforms. Many graphics libraries and APIs expose a bitblt-like function, with variants such as copying from a bitmap to a window, moving regions within the same surface, or performing masked or color-keyed transfers. Hardware acceleration in GPUs commonly handles bitblt operations as fast memory-to-memory copies or texture blits, optimized for throughput and memory bandwidth. Performance depends on factors such as alignment, cache locality, pixel format, clipping, and the availability of hardware blitters.

Bitblt operations are widely used in user interface toolkits for window movement, in image editors for cut-and-paste or layer compositing, and in 2D games for sprite handling and scrolling. While the terminology may vary, the underlying concept remains: copying or combining pixel data between buffers in rectangular regions to update a display or image efficiently.