Dots, Pixels, Colors and Resolution

This section provides quick introductions of some basic graphics concepts: dot, pixel, color, and resolution.

A computer graphics is organized as a matrix of rows and columns of dots. Each dot carries a color value. The resolution of a graphics is measured by 3 parameters:

1. Horizontal resolution: The number dots within an inch in the horizontal direction.

2. Vertical resolution: The number dots within an inch in the vertical direction.

3. Color resolution: The number of colors supported on a dot.

For example, if a graphics of 5 inches by 3 inches is stored in computer with a resolution of 72 DPI (Dots Per Inch) in both directions and 256 colors per dot, it will be stored with a matrix 3 x 72 = 216 rows and 5 x 72 = 360 columns of dots. A color value in the range of 0 and 255 is used on each dot.

A dot is also called pixel, a short name for pic-ture el-ement.

The size of a computer graphics can be easily calculated by its pixel size and number of colors, if it is stored without any compression. For example, the file size of a graphics of 360x216 pixels and 256 colors will be 360 x 216 x 8 bits = 77,760 bytes.

Last update: 2013.