blit

Blitting, short for bit block transfer, is a graphics operation that copies a rectangular block of pixels from a source image or buffer to a destination buffer. The basic form performs a direct memory transfer, but many blits also handle format conversion, clipping to the destination bounds, and simple pixel processing such as transparency, masking, or alpha blending.

Historically, blitters were implemented as dedicated hardware or as optimized software routines to speed up rendering, especially in 2D graphics systems. Early personal computers and game consoles used blitters to move sprite data and tile graphics into video memory with minimal CPU overhead. The term blit itself is derived from bit-block transfer and is still used in various APIs and tooling, such as the BitBlt function in Microsoft Windows, which copies bitmap data between device contexts.

Common blit operations include: plain copy of a pixel rectangle; transparent or masked copying using a color key or alpha channel; and more complex compositing where source pixels are blended with destination pixels. Some advanced blitters support scaling, rotation, or filtering during the transfer, though these are often handled by separate stages or more capable GPU features.

In modern graphics, blitting remains a fundamental primitive, implemented in GPUs and 2D acceleration libraries as memory-to-memory copies, texture-to-framebuffer transfers, and render-to-texture operations. While terminology and hardware have evolved, the basic concept of efficiently moving blocks of pixel data remains central to real-time rendering and image processing.