Bit blit

Bit blit (also written BITBLT, BIT BLT, BitBLT, Bit BLT, Bit Blt etc., which stands for bit block transfer) is a computer graphics operation in which several bitmaps are combined into one using a boolean function.

The operation involves at least two bitmaps, one source and destination, possibly a third that is often called the "mask" and sometimes a fourth used to create a stencil. The pixels of each are combined bitwise according to the specified raster operation (ROP) and the result is then written to the destination. The ROP is essentially a boolean formula. The most obvious ROP overwrites the destination with the source. Other ROPs may involve AND, OR, XOR, and NOT operations. The Commodore Amiga's graphics chipset, for example, could combine three source bitmaps according to any of 256 boolean functions of three variables.