Page 65 - DCAP303_MULTIMEDIA_SYSTEMS

Unit 4: Image

set of 3 primary colours: red, green, and blue. So does your television. If you go up close to your notes
TV, (put your eye right on top of the screen) you will see little dots of red, green and blue. In
computers and television, light transmissions are creating the colour. Red and green mix to create
yellow (See Figure 4.19).

figure 4.19: red and Green Mix to Create yellow

This is called “Additive Colour” and is completely different from how colours are mixed in the
tangible world of paints and pigments. When we mix red and green paint, we get muddy browns.
This is “Subtractive Colour” and is based on the primaries, red, yellow, and blue (or red-based/
magenta, yellow-based/yellow, blue-based/cyan).
Let’s take a look at the colour below (See Figure 4.20) and analyze the processes it passed through
before it reached your eyes.
figure 4.20: Colour recipe (red=204, Green=102, Blue=102)

First, the colour was created in Adobe Photoshop. The recipe for the colour you see is: red=204,
green=102, blue=102. The true colour could be called a muted coral or dull salmon.
Here is the path that the graphic took to get to you:

1. The image was placed in an html script (Web page) that can be read by all Web browsers.
This script was sent to the Colour Matters’ Web server.

2. Your Web browser software connected your computer to our server and brought the
image into your computer. The colours in this gif image passed through the browser
and brought this information into your computer operating system.
3. The colours in the image also passed through your operating system hardware. If you
have a graphic card or video card it also interpreted the colour.
4. Your monitor took all the information and sent it to your eyes.
In conclusion, remember that different computers do different things, many “systems” have
different configurations of all of the above things, and browsers used to view the World Wide
Web are part of the overall picture.

4.6 Colour palettes

A device which converts the logical colour numbers stored in each pixel of video memory
into physical colours, normally represented as RGB triplets, which can be displayed on the
monitor. The palette is simply a block of fast RAM which is addressed by the logical colour
and whose output is split into the red, green and blue levels which drive the actual display
(e.g. CRT).

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