This document provides an overview of computer graphics concepts including: - Definition and components of computer graphics - SRGP (Simple Raster Graphics Package) for drawing shapes and handling basic interactions - Raster graphics features like canvases, clipping, and copy pixel - Limitations of SRGP - Display technologies like raster scan displays, random scan displays, and video controllers - Input devices for user interaction like locators, keyboards, and logical input/output

3.  Definition
 Classification of Computer Graphics
 Components of Computer Graphics
 SRGP (Simple Raster Graphics
Package)
 Drawing with SRGP (With Example)
 Basic Interaction Handling
 Raster Graphics Features
 Limitation of SRGP

4.  Hard Copy Technologies
 Display Technologies
 Raster Scan Display
 Random (Vector) Scan Display
 Video Controller
 Raster Scan Display Processor
Thank
You!

5. Computer Graphics is the field of computer
science in which we are interested in
generating objects and images using pixels
(Picture Element)
The same showing Titanic in the sea
was possible through graphics designing
with MAYA software
The movies are like Spiderman,
Superman, X-Man and Batman and so on
have generated special effect using
computer Graphic.

7. Computer Programme is a collection of
algorithm and data structure. In the
same convention computer graphics has
been defined as the collection of data
structure, graphics, algorithm and any
higher level language. We can use any
of the higher language like C, C++, Java
or any of the graphic package like
MAYA, 3D MAX, Blender and Flash to
generate graphics of our choice.

9. Computer Graphics is the discipline of
producing picture or image using a
computer including modelling creation
manipulation and storage of geometric
objects and converting a scene to an
image or the process of transformation,
shading rasterization of the image.

10. 1. Passive Computer Graphics:-
This is also called offline graphics.
Once the graphics programme is develop
the user has no control over the display
even if he or she wishes to change display
they cannot
For example:-
Screen Saver, Gif file,
passive Graphics can be compared to
static webpages using (HTML), where user
has no control over the contents.

12. 2. Interactive Computer Graphics:-
This is also called online graphics.
User can dynamically control the display on
the monitor. Display are controlled by
mouse, trackball and joystick. This is also
called (ICG) because, the user can indirect
with the machine.
For example:-
Videogames, CAD
(Computer Aided Design) and Computer
Generated image.

13. Interactive Computer Graphics
Video Games

14. 1. Digital Memory Buffer:-
This is the place
where images or pictures are stored as an
array (Matrix of 0 and 1), 0 represent darkness
and 1 represent image or picture.
This is also called frame buffer and it help to
store image in bit form.
2. TV Monitor:-
Monitor helps us to view the
display and they make use of CRT (Cathode
Ray Tube)

15. 3. Display Controller:-
It is in interface b/w
digital memory buffer and TV monitor. It’s job is
to pass the content of frame buffer to the
monitor.
The display controller reads each succession
byte of data from frame buffer memory and
converts 0’s and 1’s into video CD.

16.  SRGP stands for simple Raster Graphics Package.
 SRGP consists of library functions that describe custom
data types and constants.
 SRGP procedures operate on canvases (Painting
Board), which is a 2D array of pixels (virtual frame
buffer).
 The depth will be the number of planes requested by
designated application.
 Every canvas has its local coordinate system.
 Multiple windows cannot be controlled by SRGP
application
The origin for the local coordinate system is the
lower-left corner of the canvas, with the x-coordinate
increasing to the right and the y-coordinate increasing
toward the top.

17. Drawing in integer raster graphics
packages such as SRGP is like plotting
graphs on graph paper with a plotting
graphs on graph paper with a very fine
grid. The grid varies from 80 to 120
points per inch on conventional display
to 300 or more on high-resolution
display.

18. For example:-
Now we draw a pixel (200,300) on 1366 x 768 pixel screen.
Program-
#include<stdio.h>
#include<conio.h>
#include<graphics.h>
Void main()
{
int gd=DETECT, gm;
clrscr();
initgraph(&gd, &gm, “C:TCBGI”);
putpixel(200,300, WHITE);
getch();
closegraph();
}

19. Steps:-
1. First you figure out where the origin(0,0) is.
2. Then what primitives (line, pixel, circle,
rectangle ellipse and triangle) are provided
to you.
3. And what attributes these primitives can
have such as for line-
𝑙𝑖𝑛𝑒(𝑥1, 𝑦1, 𝑥2, 𝑦2)
Where-
𝑥1- x coordinate of starting point.
𝑦1- y coordinate of starting point.
𝑥2- x coordinate of ending point.
𝑦2- y coordinate of ending point.

20. Output:- Screen Resolution(1366x768)
.

22. 1. Canvases:-
An SRGP canvas is a data
structure that stores an image as a 2D array of
pixels. It is also stores some control information,
the size and attributes of the image.
Canvas is an area of memory which is used as
a buffer between graphics software and
graphics hardware.
Once canvas is create its size cannot changed.
𝑖𝑛𝑡 𝑆𝑅𝐺𝑃_𝑐𝑟𝑒𝑎𝑡𝑒𝐶𝑎𝑛𝑣𝑎𝑠(𝑖𝑛𝑡 𝑤𝑖𝑑𝑡ℎ, 𝑖𝑛𝑡 ℎ𝑒𝑖𝑔ℎ𝑡);

23. Canvas

24. It is desirable to restrict the effect of
graphics primitives to a sub region of the
active canvas. To facilitate this, SRGP
maintains a clip rectangle attribute. Likes
any attribute, the clip rectangle can be
changed at any time, and its most recent
setting is stored with the canvas’s attribute
group.
Portion which is either inside or
outside of specific region or space called
as clipping.
Here the default clipping rectangle is the
full canvas, so we can call it clipping
rectangle.

25. It is often called bitBlt (bit block transfer) or
pixBlt (pixel block transfer) when
implemented directly in hardware.
𝑣𝑜𝑖𝑑 𝑆𝑅𝐺𝑃_𝑐𝑜𝑝𝑦𝑃𝑖𝑥𝑒𝑙(𝑖𝑛𝑡 𝑠𝑜𝑢𝑟𝑐𝑒𝐶𝑎𝑛𝑣𝑎𝑠𝐼𝐷,
𝑟𝑒𝑐𝑡𝑎𝑛𝑔𝑙𝑒 𝑠𝑜𝑢𝑟𝑐𝑒𝑅𝑒𝑐𝑡, 𝑝𝑜𝑖𝑛𝑡 𝑑𝑒𝑠𝑡𝐶𝑜𝑟𝑛𝑒𝑟);

26. Guidelines-
• It can implemented as nested for loop for
each pixel.
• It can do more than just move an array of
pixel from source to destination.
• Copy pixel was faster within local image
memory.
• copyPixel that can make copy subject to one
or more source read or destination write task.
• CopyPixel facility is available to write multi-
pixel.

28. • SRGP provides no support for displaying 3D
geometry applications.
• It does not support object level operations,
such as “delete”, “move”, “change colour”,
because SRGP keeps no record of the
actions.
• Multiple windows cannot be controlled by
SRGP application.
• It cannot refresh a screen a screen if the
image is damaged by other software.
• It cannot rescan convert the primitives(lines,
rectangles, circle and arc etc.) to produce an
image for display on a device with a different
resolution.

29. Hard Copy Technology
We can obtain hard-copy output for our
image in several formats for presentations,
we can send image files to devices or
services that will produce 35 mm slides. To
put image on film, we can simply
photograph a scene displayed on a video
monitor and we can put our pictures on
paper by directing graphics output to a
printer or plotter.
The Quality of the pictures obtained from a
device depends on dot size and the
number of dots per inch, or lines per inch,
that can be displayed.

30. Hard Copy Technology
Printers produce output by either impact
and nonimpact.
:-
Impact printers press formed
character faces against an inked ribbon
onto the paper.
Example:- A line printer, Dot-Matrix
Printer, Daisy-Wheel Printer, Drum
Printer, and Chain Printer.

32. Hard Copy Technology
:-
Nonimpact printers and plotters
use laser techniques, ink-jet sprays,
xerographic processes (using in
Photocopying machines), electrostatic
methods and electro thermal methods
to get image onto paper.
Example:- Laser Printer, Ink-jet Printer,
Thermal Printer and plotter.

34. Display Technology
The display device developed in the mid
1960 and in common use until the mid
1980 are called.
• Vector
• Stroke
• Line Drawing
• Calligraphic Display

35. Display Technology
CRT (Cathode Ray Tube)
• Raster Display
• Random Display
LCD (Liquid Crystal Display)
LED (Light Emitting Diode)

36. CRT (Cathode Ray Tube)
The quality of display image is every
important in most application on computer
graphics.
CRT was the only available device, which
was capable of converting computer
electrical signal in variable image at high
speed.
CRT is the best suited for ICG (Interactive
Computer Graphics), a beam of electron.
Cathode Ray emitted by electron gun and
passes through focussing and deflection
system that direct the beam on a point on
the phosphor codded is uses

37. Cathode Ray Tube

38. Cathode Ray Tube
:-
In raster scan system, the electron
beam is swept across the screen, one row
at a time from top to bottom. As the
electron beam moves across each now,
the beam intensity is turned on and off.
Picture definition is stored in memory area
called refresh buffer or frame buffer. The
memory area hold the set of intensity
value for all the screen point. Each screen
point is referred to as pixel.

39. Raster Scan Display

40. Raster Scan Display

41. Simple Raster Display System
System Bus
CPU
Frame
Buffer
System
Memory
Video
Controller
Monitor
Peripheral
Devices

42. Cathode Ray Tube
:-
In this technique, the electron beam is
directed only to the part of the screen, where
the picture is to be drawn rather scanning from
left to right and top to bottom as Raster scan. It
also called vector display, Stroke writing
display. Picture definition is stored as a set of
line drawing and on an area of memory
referred to as the refresh display file to display
a specified picture the system cycles through
the set of commands are processed, the
system cycles back to the first line command in
the list.

43. Random Scan Display

44. Random Scan Display

45. Random Display System
System Bus
CPU
Display
Processor
System
memory
Monitor
Peripheral
Device

46. Random Scan Display Raster Scan Display
It can only draw lines and
characters using
mathematical formulae and
functions.
[Perfect for “Painting”]
It can draw filled with
colours (Complex
Drawings).
[Perfect for “Drawing”]
Video controller is not
required.
Video Controller is required.
Electronic beam is directed
to only part where image is
to be drawn.
Electronic Beam is directed
to whole screen for drawing
an image or object.
Picture definition is stored
as set of line drawing
instructions(command) in a
refresh display file.
Picture definition is stored
as group of points or set of
points known as pixels in a
refresh buffer area.
It is more expensive and
high resolution.
Small file size
It is less expensive and
global resolution.
Large file size
Editing is easy (picture
clarity does not affect)
Editing is difficult (Picture
quality affect according to
raster application )

47. Video Controller
A fixed area of the system memory is
reserved for frame buffer and the video
controller is given direct access to the
frame buffer memory.
It is an expansion card whose function is
to generate and output images to a
display. When referring to early machines,
the card is sometimes referred to as a
graphics controller, when the cards were
typically integrated onto the motherboard
itself.
Such as graphic card

48. Video Controller
For example:-
You are asking a local resident
directions to a hotel. You cannot understand
anything this person is telling you no matter
how hard you listen. Luckily, someone who
speaks their language and yours approaches
the person and begins translating for the both
of you. After a few exchanges of dialogue, you
are able to obtain the directions and make your
war to the hotel. A video card works in the
exact same way. Without it, a picture would
never appear on our computer monitors and we
would constantly be viewing a blank screen,
making the computer completely useless.

49. Raster Scan Display Processor
Raster System containing a separate
display processor, sometimes referred to
as a graphics controller or a display
coprocessor.
The purpose to display processor is to free
the CPU from the graphics cores.
Display processor are designed to-
• Digitizing a picture definition given in an
application programme into a set of pixel
intensity value for storage in the frame
buffer. This digitization process is called
scan conversion.

50. Raster Scan Display Processor
• Perform additional operations such as-
• Generating various line style (dashed,
doted and solid).
• Displaying colour areas.
• Performing transformations and
manipulations on displayed object.
• Interface with interactive input devices
such as mouse.

51. Input Device for Operator
Interaction
There are five basic logical devices:
1. Locator: To indicate a position or
orientation.
• Tablet
• Trackball
• Joystick
• Touch panel
• Light pen
• Mouse
2. Pick: To select a displayed entity.
3. Valuator: To input a single real number.
4. Keyboard: To input a character strings.
5. Choice: To select from a set of possible
actions or choices.

52. Once you how to draw basic shapes and text, your next step is to
learn how to write interactive programs that communicate
effectively with the user.
1. Human Factors:-
The designer of an interactive
program must deal with many matter that do not arise in a non
interactive, batch program, they are called human factors of a
program, such as its look and feel and its ease of learning and of
use.
Guidelines:-
a. Provide simple and consistent interaction sequences.
b. Do not overload the user with too many different options and
styles.
c. Show the available options clearly at every stage of the
interaction.

53. 2. Logical Input/output Devices:-
A major goal
in designing graphics packages is device
independence, which enhances portability of
applications.
a. Logical Input Devices:-
Support for a set of logical input
devices.
Two types of devices-
i. Locator-
A device for specifying screen
coordinate and the state of one or more associated
buttons.
ii. Keyboard-
A device for specifying character string

55. b. Logical Output Device-
• Primitives are specified in terms of an
abstract integer coordinate system .
• The application does not need to set
the individual pixels in the frame
buffer.

56. c. Sampling versus event driven
processing-
There are two fundamental
techniques for receiving information
created by user interactions.
i. Sampling (Polling)
ii. Interrupt/Event Driven