Bit block transfer, also known as bitblt, is an operation used in computer graphics programming to move a block of bits from one location in memory to another. This process is commonly used in GUI code to quickly display images, icons, and font characters on a screen.
The primary purpose of bit block transfer is to transform blocks of pixels and change the color value or shade of a block of pixels. Additionally, it can change the orientation of a visual image to transfer graphics faster than conventional means. This process is achieved through the use of a blitter and dedicated circuit intended to copy large amounts of data and send it to a certain memory storage area.
The process of bit block transfer typically involves at least two bitmaps – a source and a destination – and possibly a third called a mask. The pixels of each bitmap are combined bit by bit using a specified raster operation (ROP) and then written to the destination. ROP is a Boolean formula, and the most obvious ROP is to overwrite the destination with the source. The Commodore Amiga graphics chipset could combine three source bitmaps with any of 256 possible Boolean functions with three inputs.
Bit block transfer is widely used in the field of graphic design and computer graphics programming. The operation is so widespread that many modern microprocessors provide special instructions to speed it up, and hardware graphics accelerators often contain dedicated units called blitters that work as fast as possible. The word “blit” is rumored to mean “interactive bacon, lettuce, and tomato.”
Frequently Asked Questions (FAQ)
- What is bitblt used for?
- What is a blitter?
- What is ROP?
Bit block transfer is used for moving a block of bits from one location in memory to another, which is especially useful in GUI code for quickly displaying images, icons, and font characters.
A blitter is a dedicated circuit for copying large amounts of data and sending it to a certain memory storage area. It is commonly used in bit block transfer to transfer graphics faster than conventional means.
ROP stands for Raster Operation and it is a Boolean formula used in bit block transfer to combine pixels bit by bit according to the specified formula.
In conclusion, bit block transfer is a vital process in computer graphics programming and is used to quickly display images, icons, and font characters on a screen. It involves at least two bitmaps and uses raster operation to combine pixels bit by bit. Dedicated circuits called blitter are used to transfer graphics faster, and many modern microprocessors have special instructions to speed up the operation.