1. Definition

BitBlt (Bit Block Transfer) is a raster graphics operation that copies a block of pixels from a source to a destination in memory or on a display.

• It is a low-level graphics operation used in windowing systems, GUIs, and 2D graphics.
• Allows fast manipulation of images, sprites, or regions of the screen.
• Typically used in systems like Windows GDI (Graphics Device Interface).

2. Basic Concept

• Copy a rectangular pixel block (bitmap) from a source to a destination.

• Can include masking, raster operations, and combining pixel values.

• Parameters typically include:

  • Source coordinates $(x_s, y_s)$
  • Destination coordinates $(x_d, y_d)$
  • Width and height of the rectangle
  • Raster operation (ROP)

3. Raster Operations (ROPs)

ROPs define how source, destination, and optional mask pixels are combined.

Common ROPs include:

• These operations allow effects like masking, transparency, and inversion.

4. Applications of BitBlt

1. Moving or copying windows on the screen.
2. Double buffering: Draw off-screen and copy to the screen to avoid flicker.
3. Sprite animation in games.
4. Image manipulation: overlaying, inverting, masking.

5. BitBlt Process

1. Define source rectangle: select the block of pixels to copy.
2. Define destination rectangle: where to place the copied block.
3. Apply raster operation (ROP): determines how pixels are combined.
4. Transfer pixels efficiently using hardware acceleration when available.

6. Advantages

• Fast: Optimized for block copying of pixels.
• Flexible: Supports masking, transparency, and logical operations.
• Fundamental in 2D GUIs: Used for window movement, screen updates, and animations.

Key Points:

• BitBlt = copying a block of pixels with optional raster operations.
• Essential for efficient 2D graphics, windowing systems, and off-screen drawing.
• Works with source, destination, and mask for powerful visual effects.