Course pages 2012–13

**Subsections**

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Computer Graphics and Image
Processing

*Lecturer: Professor P. Robinson & Professor N. Dodgson*

*No. of lectures:* 16

*Suggested hours of supervisions:* 4

*Prerequisite courses: Algorithms*

*This course is a prerequisite for Advanced Graphics (Part II).*

### Aims

To introduce the necessary background, the basic algorithms, and the
applications of computer graphics and image processing. A large
proportion of the course considers the design and optimisation of
algorithms, so can be considered a practical application of the
lessons learnt in the *Algorithms* course.

### Lectures

**Background.**What is an image? What are computer graphics, image processing, and computer vision? How do they relate to one another? Image capture. Image display. Human vision. Resolution and quantisation. Colour and colour spaces. Storage of images in memory, and double buffering. Display devices: brief overview of two display technologies (LCD, DMD) and two printer technology (ink jet and laser printer). [3 lectures]**2D computer graphics.**Drawing a straight line. Drawing circles and ellipses. Cubic curves: specification and drawing. Clipping lines. Filling polygons. Clipping polygons. 2D transformations, vectors and matrices, homogeneous co-ordinates. Uses of 2D graphics: HCI, typesetting, graphic design. [4 lectures]**3D computer graphics.**Projection: orthographic and perspective. 3D transforms and matrices. 3D rotation using a non-matrix method. 3D clipping. 3D curves. 3D scan conversion using the z-buffer. Anti-aliasing and the A-buffer. Lighting: theory, BRDF, approximations: flat shading, Gouraud shading, Phong shading. Texture mapping. OpenGL programming. [7 lectures]**Image processing.**Operations on images: filtering, point processing, compositing. Halftoning and dithering, error diffusion. [2 lectures]

### Objectives

At the end of the course students should be able to

- explain the basic function of the human eye and how this impinges on resolution, quantisation, and colour representation for digital images; describe a number of colour spaces and their relative merits; explain the workings of two display technologies and two printer technologies;
- describe and explain the following algorithms: mid-point line drawing, mid-point circle drawing, Bezier cubic drawing, Cohen-Sutherland line clipping, scanline polygon fill, Sutherland-Hodgman polygon clipping, -buffer, -buffer, texture mapping, error diffusion;
- use matrices and homogeneous coordinates to represent and perform 2D and 3D transformations; understand and use 3D to 2D projection, the viewing volume, and 3D clipping;
- understand Bezier curves and patches; understand sampling and super-sampling issues; understand lighting techniques and how they are applied to z-buffer polygon scan conversion; understand texture mapping;
- explain how to use filters, point processing, and arithmetic operations in image processing and describe a number of examples of the use of each; explain how halftoning, ordered dither, and error diffusion work.

### Recommended reading

* Foley, J.D., van Dam, A., Feiner, S.K. & Hughes, J.F. (1990). *Computer graphics: principles and practice*. Addison-Wesley (2nd ed.).

Gonzalez, R.C. & Woods, R.E. (2008). *Digital image processing*. Addison-Wesley (3rd ed). [The second edition (1992) and the first edition (Gonzalez & Wintz, 1977) are as useful for this course.]

* Slater, M., Steed, A. & Chrysanthou, Y. (2002). *Computer graphics and virtual environments: from realism to real-time*. Addison-Wesley.