This document provides an introduction to computer graphics. It defines computer graphics as the creation, representation, manipulation and display of pictures with a computer. It discusses the key components of computer graphics including modeling, storing/representation, manipulation/transformation, rendering, interaction, and viewing/presentation. It also covers related concepts like pixels, resolution, aspect ratio, and the differences between raster and vector displays. Finally, it discusses applications of computer graphics and different character generation methods.

1. Introduction
to
Computer Graphics
Presented by
Education Success

2. Introduction
 Computer Graphics :-
• Def. :- Computer graphics (CG) is the creation,
representation, manipulation and display of
picture with the help of computer.
• Graphics is the ability for giving computer to
express its data in pictorial form.
• Computer graphics may be interactive or non-
interactive.

3. Components of Computer Graphics
1. Modeling
2. Storing/Representation:
3. Manipulation/Transformation
4. Rendering
5. Interaction
6. Viewing / Presentation

4. Components of Computer Graphics
1. Modeling :-
It deals with the definition of the object in terms of the primitives,
coordinates and characteristics. In computer graphics, an object is made up
by pixels so it deals with the object definition in terms of pixels, their
address and intensity values.
2. Storing/Representation :-
It deals with the storing scenes and images in memory and on disk. It is
used to know how the picture is internally stored in computer. Objects,
images or scenes are stored in computer in binary representation. So it deals
with binary representation of pixels to define the object, scenes and images.
3. Manipulation/Transformation :-
It deals with the changing the shape, position and characteristics of objects.
It also includes various operations such as translation, rotation, scaling and
clipping.

5. Components of Computer Graphics
4. Rendering :-
It deals with the applying physically based procedures to generate
(photorealistic) images from scenes (using lighting and shading)
5. Interaction :-
Interaction of the user can be achieved by hardware and software
combination. It helps user to select or pick an object with the help of
input devices such as mouse, light pen.
6. Viewing / Presentation:
It deals with the displaying images. We can display the object in
two-dimensional and three-dimensional form on two-dimensional
devices.

6. Applications of Computer Graphics
• CAD (Computer Aided Design):
• Presentation Graphics
• Computer Art
• Education and Training
• Entertainment
• Visualization
• Image Processing
• GUI (Graphical User Interface )

7. Concepts in Computer Graphics
• Pixel
• Resolution
• Aspect Ratio
• Raster Vs Vector

8. Pixel / Pel / Picture Element
• Graphics images on the screen are built-up from
tiny dots or points called “pixels”.
• It is also called as “pixel” or “pel” i.e. Picture
element. The pixel is smallest possible screen
elements.
• Each pixel has a name and address. This address
corresponds to the co-ordinates points on the
screen which identify points.
• Each point must have some size.
• We can also set the intensity and color of the
pixel.

9. Resolution
• Def. :-
a) The maximum number of points that can be display without overlap on a
CRT is called, “resolution” . or
b) The number of points per cm that can be plotted horizontally and vertically
are the, “resolution.” or
c) The number of points in each direction is called, “resolution”.
• The display resolution is define by the number of rows from top to bottom
and number of columns from left to right on each scan light.
• Higher resolution means more sharp and clear picture. Greater the number of
points, the higher resolution.
• Eg. :- Typical resolution of the screen is 1280 x 1024 , it means 1280 pixels in
each row and 1024 in each column.
• Other screen resolutions are
- 640 x 480
- 800 x 600
- 1024 x 768
- 1152 x 864
- 1280 x 1024

10. Aspect Ratio
It is a ratio of vertical points to the horizontal points, necessary
to produce equal length lines in both directions on screen.
In the above example, aspect ratio of 3 by 4 means that a vertical
line plotted with 3 points has same length as a horizontal line
plotted with 4 points.
Aspect ratio is a property of video monitor. If a picture has aspect
ratio of 2:1, it means width is twice as large as the height of that
picture. While resizing picture, it is important to obtain the aspect
ratio otherwise the picture may get stretched and gets distorted.

11. Raster Display
• In raster form, intensity values of the pixels of the
picture are stored in the memory area, called frame
buffer.
• Here, picture is stored as a rectangular array or grid with
intensity values of the all the pixels of picture part.
• It uses bitmap method of character generation.
• It requires higher refresh rate, because it refreshes all
pixels whether it is a part of not a part of picture.
• It can display the realistic and shaded scene.

12. Vector / Random Display
• In vector form, picture is stored with only end points and
line drawing commands in memory area called, display
file.
• It uses stroke method of character generation.
• It requires lower refresh rate than raster form, because it
refreshes only picture part and endpoints of that picture
element.
• It cannot display realistic and shaded scene.
• Here, order of refreshing is random and it has high clarity
because it retains appearance regardless of size of image.

13. Character Generation Methods
1. Stroke Method ( Vector Method )
2. Dot-Matrix Method ( Bit-Map Method )
3. Starbust Method

14. Stroke Method ( Vector Method )
This method creates characters out of a series of line segments,
like strokes of a pen, as shown in fig.
Fig. :- Stroke method for character ‘A’
We can decide which line segments needed for each character
that we want to draw. To produce a character , we give a sequence
of commands that defines the start point and end points of the
straight lines.

15. Dot-Matrix Method ( Bit-Map Method )
This method is called as, “Bitmap method”. In this method,
characters are represented by an array of dots, as shown in
fig. (a) and (b)
Fig. (a) - Bit map method for character ‘A’

16. Fig. (b) – Bitmap method for character ‘B’
• A bitmap font uses a rectangular pattern of pixels to define
each character.
• It requires more space, because each variation (size or format)
must be stored in memory.

17. Starbust Method
• In this method a fix pattern of line segments are used to
generate characters.
• There are 24 line segments and out of these 24 line
segments, segments required to display for particular
character are highlighted. This method of character
generation is called, “Starbust method” because of its
characteristics appearance.
• In this pattern of particular character is stored in the form
of 24 bit code. Each bit representing one line segment.
The bit is set to one to highlight the line segment.
Otherwise it is set to zero.

18. • Eg. :- The starbust patterns for characters A and M
• 24-bit code for Character ‘A’ is 0011 0000 0011 1100 1110
0001 and
• 24-bit code for character ‘M’ is 0000 0011 0000 1100 1111
0011

19. Disadvantages of starbust method
• It requires more memory.
• It requires additional code conversion
programs to display characters from the 24 bit
code.
• Requires code conversion software to display
character from its 24-bit code
• Character quality is poor. It is worst for curve
shaped characters.
• This method is not used now-a-days.

20. Thank You