1

Introduction to Computer Graphics

2

3

What is Computer Graphics?

A computer is a device capable of storing data

in a format suited to the computer, which is then processed by

mathematical manipulation and correlation of data.

Graphics is the way in which data is displayed after the processing has been performed.

4

Reason behind Computer Graphics

The Movie Industry. Gaming Industry Medical Imaging and Scientific Visualization Computer Aided Design

5

Advantages

1. High quality graphics display. [Win7]

2. Ability to reproduce not only real-world objects but abstract objects too. [Car design]

3. Animation

4. Parameters under our control: Speed, part or full scene view, Geometrical relationship with of the objects in the scene wrt other objects.

6

Advantages Continued…

4. Builders use CAD for creating walkthroughs to be presented to the clients.

5. Motion dynamics

6. Update dynamics

7. Audio + Video output gives a realistic look.

7

Realism

8

How is the data displayed???

Data Display

Text Object

9

Picture Element => Pixel => Pel

The smallest addressable screen element.

A pixel need not represent just a single point.

A pixel rather represents a region which can contain a number of infinite points.

10

What does a pixel contain???

A pixel contains:

Co-ordinates

Intensity

Color

11

Pixel Approximation

Special procedures are required to determine which pixel will provide the best approximation to the desired picture or graphics object.

RASTERISATION

SCAN CONVERSION

12

Types of images

JPEG Vector Bitmap TIFF ……

13

Vector

In physics, a vector is defined as having magnitude as well as direction.

A vector file is sometimes called a geometric file.

Vector graphics is the use of geometrical primitives such as points, lines, curves, and shapes or polygon(s), which are all based on mathematical equations, to represent images in computer graphics. [eg: Maps]

14

Vector Graphics

It is the creation of digital images through a sequence of commands or mathematical statements that place lines and shapes in a given 2D or 3D space.

The work of a graphics artist’s work is saved as a vector graphic file.

This is eventually converted to bitmap file in order to port it between systems.

15

Advantages of vector graphic

It is not resolution dependent hence scalability (resizing) of the image does not result in loss of image quality. [Logos, maps]

Control points help in resizing the object.

A graphic file does not contain the image itself, rather it contains the mathematical equations.

16

Disadvantages of vector graphic

Drastically minimizing the object may result in the erosion of fine lines but the picture quality remains the same. Too much enlargement can make the mistakes visible.

Although photorealistic look is possible but still most vector images look like sharply drawn cartoon images.

17

Bitmap image

An image made up from individual pixels is often referred to as a bitmap or a pixmap image.

It is a spatially mapped array of bits i.e pixels known as a map-of-bits

18

Bitmap

Vector V/s Bitmap

Raster images are based on pixels and thus scale with loss of clarity, while vector-based images can be scaled indefinitely without degrading quality.

19

Rasterized bitmap image of a vectorial image

20

QUIZ#1

Which of the following devices is a graphics device?

Keyboard

Joystick

Printer

LCD

Mouse

Touch Screen

21

Summary

Vector images are a collection of individual objects rather than picture elements.

A vector image can be composed of points connected by lines, or nodes (control points) connected by Bezier curves.

Animation images are also usually created as vector files. Example, Shockwave's Flash product lets you create 2-D and 3-D animations that are sent to a requestor as a vector file and then rasterized "on the fly" as they arrive.

22

Color Depth

23