Editing Bit blit (section)

{{Short description|Data operation used in computer graphics}}
{{one source|date=December 2017}}
'''Bit blit''' (also written '''BITBLT''', '''BIT BLT''', '''BitBLT''', '''Bit BLT''', '''Bit Blt''' etc., which stands for ''bit block transfer'') is a data operation commonly used in [[computer graphics]] in which several [[bitmap]]s are combined into one using a ''[[Truth_table#Binary_operations|boolean function]]''.<ref name="Sanchez"/>

The operation involves at least two bitmaps: a "source" (or "foreground") and a "destination" (or "background"), and possibly a third that is often called the "[[stencil|mask]]". The result may be written to a fourth bitmap, though often it replaces the destination. The pixels of each are combined using a program-selectable ''raster operation'', a bit-wise [[Boolean logic|boolean]] formula. The most obvious raster operation overwrites the destination with the source. Others may involve [[Logical conjunction|AND]], [[Logical disjunction|OR]], [[XOR]], and [[negation|NOT]] operations.<ref name="Sanchez">{{cite book|last=Sanchez|first=Julio |author2=Maria P. Canton|title=Software solutions for engineers and scientists |publisher=CRC Press|date=2007|pages=690|chapter=Displaying Bit-Mapped images|isbn=978-1-4200-4303-7 |chapter-url=https://books.google.com/books?id=jtKc0k5BWA8C&pg=PA690}}</ref> The Commodore [[Amiga]]'s graphics chipset (and others) could combine three source bitmaps using any of the 256 possible 3-input [[boolean function]]s.

Modern graphics software has almost completely replaced bitwise operations with more general mathematical operations used for effects such as [[alpha compositing]]. This is because bitwise operations on color displays do not usually produce results that resemble the physical combination of lights or inks. Some software still uses XOR to draw interactive highlight rectangles or region borders; when this is done to color images, the unusual resulting colors are easily seen.