Bits per pixel

Color depth is a computer graphics term describing the number of bits used to represent the color of a single pixel in a bitmapped image or video frame buffer. The term bits per pixel (bpp) is often used interchangeably.

Indexed color

With relatively small numbers of colors, the stored value is typically an index into a color map or palette. The colors available in the palette itself may be fixed by the hardware or modifiable.

• 1-bit color (2¹ = 2 colors) monochrome, often black and white
• 2-bit color (2² = 4 colors) CGA
• 4-bit color (2⁴ = 16 colors) as used by the least common denominator VGA standard
• 8-bit color (2⁸ = 256 colors)

Direct color

As the number of bits increases, the number of possible colors becomes impractically large for a color map. In higher color depths, the color value typically directly encodes relative brightnesses of red, green, and blue to specify a color in the RGB color model.

• 16-bit uses 16 bits to create life-like colors, with a total of 65536 colors. Sometimes called "Hi-Color"
  • Red, green, and blue components often take up 5 bits each (2⁵ = 32 levels), this is sometimes called 15-bit color
  • Sometimes one element is expanded to 6 bits (2⁶ = 64 levels), usually green. Other times the extra bit is left empty.
• 24-bit color values can represent 16777216 distinct colors. This type of color is called true color, since it can potentially mimic many colors found in the real world.
  • Each component is 8 bits deep (2⁸ = 256 levels). This approaches the level at which the human eye can distinguish colors for most photographic images, though image manipulation or "pure" generated images may reveal the limitations.
• "32-bit color" usually refers to 24-bit color with an additional 8 bits either as empty padding space or to represent an alpha channel

In graphics intensive applications like computer games, a tradeoff of performance vs quality can be achieved by raising or lowering the color depth of the display.