• 1. Computer Graphics
  • 1.1. Screen
  • 1.2. Colours
  • 1.3. Rasterisation
    • 1.3.1. Setting the Colour of a Pixel
    • 1.3.2. Line Rasterisation
    • 1.3.3. Filling Areas
    • 1.3.4. Unit-Summary
  • 1.4. Anti-Aliasing
  • 1.5. Geometric Transformations
  • 1.6. Curves
  • 1.7. Paths
  • 1.8. Self Assessment
  • 1.9. Summary
  • 1.10. Recommended Reading
  • 1.11. Glossary
  • 1.12. Bibliography
  • 1.13. Metadata

1.3. Rasterisation

Learning Objectives

• You will be able to write down the algorithm for colouring a particular pixel of the screen.
• You will be able to choose the right pixels of the screen to draw a continuous line.
• You will be able to explain the different steps of the algorithm for filling polygons.

Introduction

Now you know something about colours in the RGB-Colour Space and their codification, but we still do not know how to tell the computer which pixel on the screen has to feature which colour. In this unit we will learn a simple algorithm that solves this problem.

Since it is often not efficient to colour each pixel separately - think of colouring a whole screen that features about one million pixels - we will demonstrate you other algorithms for setting the colour of sequences of pixels. Drawing lines on a raster display is not that simple as it seems to. Imagine drawing a diagonal straight line by only colouring tiny quadratic elements of a cartesian coordinate system. Colouring the right pixels is not always that easy. We will provide you some solutions.

Update: 26.1.2012 (eLML) - Contact - Print (PDF) - © CartouCHe 2004-2007 (Creative Commons) - layout based on YAML