Why is this important?

Any time you are involved in:
  • Developing web sites and applications
  • Digital imaging or digital photography
  • Scanning documents / archiving

Some definitions

A pixel (or Picture Element) is the smallest unit of color produced by a computer monitor. Thus,
pixels have become the de facto unit of measure for computer images (and colors).

A raster is one horizontal row of pixels, representing one line of a computer monitor or image.

The range of colors that can be produced by mixing the primary colors available in the different
intensities available is known as the Color Space.

Representing Color

For a good overview of this topic, see the Color FAQ .


Note the two alternate representations: Hue, Saturation, Luminosity and Red, Green, Blue

Hue is the color represented numerically (as going round a color wheel); Saturation is the "colorfulness" of a color; Luminosity is the brightness.

These are our two "main" ways to represent color: two systems each which needs three numbers:

We also have systems for more specialized use

Representing Images

For a general overview of the different formats for storing images, see the Wikipedia page and the Comparison chart of image formats. There are a variety of techniques generally used in image handling, particularly:

Example basic Exif tagging:


i308jpeg.jpg i308gif.gif


There are plenty of Image converters e.g. Pixillion.