Digital Images

Question 1

1. RGB Display

Answer 1

Computer monitors are made up of tiny red green and blue lights. This is called an RGB display. Red green and blue are the three primary colors of light and they can be combined to make all the colors of the visible spectrum. Each set of three lights is called a pixel. The image above uses three lights to represent a single pixel. When all three lights shine at the same time our eyes perceive them together as white light. By combining two colors you get the secondary colors of light. Red and green make yellow red and blue make magenta and green and blue make cyan. By varying the brightness of one or more of the lights each pixel can display any color on the visible spectrum.

Question 2

2. Raster Images

Answer 2

Raster (or bitmap) images are the most common kind of digital image. Computers store raster images by remembering the color of each pixel. For example a yellow pixel might take three bytes to encode one each for red green and blue. Since yellow is a combination of red and green the computer might store the yellow pixel by using eight 1s for red eight 1s for green and eight 0s for blue. When the computer interprets this data it turns the red and green lights all the way on and the blue light all the way off.

Question 3

3. Vector Images

Answer 3

The other kind of digital image are vector graphics. If you�ve ever seen a 3D computer-animated movie or video game then you�ve seen vector graphics at work. Fonts are also vectors. Instead of storing each individual pixel the computer stores points and curves. For example to create a circle a vector image may store four points then tell the computer to connect the points with quarter arcs and fill the shape with a color.