A pixel is an elementary digital image unit that does not have its own linear size. Pixel is an abbreviation for picture element (picture element).
The more pixels used to represent an image, the closer the result can resemble the original. The number of pixels in an image is sometimes called the resolution, though resolution has a more specific definition.
The number of distinct colors that can be represented by a pixel depends on the number of bits per pixel (bpp). A 1 bpp image uses 1 bit for each pixel, so each pixel can be either on or off. Each additional bit doubles the number of colors available, so a 2 bpp image can have 4 colors, and a 3 bpp image can have 8 colors:
- 1 bpp, 21 = 2 colors (monochrome)
- 2 bpp, 22 = 4 colors
- 3 bpp, 23 = 8 colors
- 4 bpp, 24 = 16 colors
- 8 bpp, 28 = 256 colors
- 16 bpp, 216 = 65,536 colors ("Highcolor")
- 24 bpp, 224 = 16,777,216 colors ("Truecolor")