1. Computer Graphics Lecture 13 Graphics Systems Taqdees A
Computer Graphics Lecture 13 Graphics Systems Taqdees A. Siddiqi

2. Video Display Devices Refresh Cathode-Ray Tubes Raster-Scan Displays
Random-Scan Displays
Color CRT Monitors
Direct-View Storage Tubes
Flat-Panel Displays
Three-Dimensional Viewing Devices

3. Refresh Cathode-Ray Tubes

4. Refresh Cathode-Ray Tubes

5. Refresh Cathode-Ray Tubes

6. Refresh Cathode-Ray Tubes Cont..

7. Refresh Cathode-Ray Tubes
Refresh CRT
Control Grid
Focusing System
Focusing in High Precision System
Construction of Cathode-Ray Tubes
Persistence
Resolution
Aspect Ratio

8. Refresh Cathode-Ray Tubes

9. Area Filling
Scan_line Fill
Boundary Fill
Flood Fill

10. Video Controller Basic Video Controller Refresh Operations
Horizontal and Vertical Deflection Voltages
Raster Scan Generator
Register X
Register Y
Memory Addresses
Pixel Register
Intensity
Frame Buffer
Basic Video Controller Refresh Operations

11. Graphics Card or Display Adaptors
A number of display Adaptors are available with varying capabilities specially Intel systems support following Adaptors:
Monochrome Adaptor (MA)
Hercules Adaptor (HA)
Color Graphics Adaptor (CGA)
Enhanced Graphics Adaptor (EGA)
Multicolor Graphics Adaptor (MCGA)
Video Graphics Adaptor (VGA)
Super Video Graphics Adaptor (SVGA)
Extended Graphics Adaptor (XGA)
                                                                        

12. Raster Scan Display Processor
Frame Buffer
Video Controller
Display Processor Memory
Monitor
Display Processor
CPU
System Memory
System Bus
I/O Devices
Architecture of a raster graphics systems with a display processor

13. Random-Scan Systems
Architecture of a simple random scan system

14. Graphics Card or Display Adaptors
A number of display Adaptors are available with varying capabilities specially Intel systems support following Adaptors:
Monochrome Adaptor (MA)
Hercules Adaptor (HA)
Color Graphics Adaptor (CGA)
Enhanced Graphics Adaptor (EGA)
Multicolor Graphics Adaptor (MCGA)
Video Graphics Adaptor (VGA)
Super Video Graphics Adaptor (SVGA)
Extended Graphics Adaptor (XGA)
                                                                        

15. Graphics Card or Display Adaptors
A video card is typically an adaptor, a removable expansion card in the PC. Thus, it can be replaced!
A video display Adaptor which is the special printed circuit board that plugs into one of the several expansion slots present on the mother board of the computer. A video display Adaptor is referred to as a video card as well.
The video card can also be an integral part of the system board; this is the case in certain brands of PCs and is always the case in laptops and clear preference for the replaceable video card in some PCs.
                                                                        

16. Source Code
Code in assembly language that can set graphics mode 19 (13h)
MOV AH,0
MOV AL,13h ;mode number from 0-19
INT 10h

17. Source Code Cont..
You can use this for assembler or you can embed this code in C language using ‘asm’ keyword
asm {
MOV AH,0
MOV AL,13h;;mode number from 0-19
INT 10h }

18. Source Code
Code in assembly language that can set graphics mode 19 (13h)
MOV AH,0
MOV AL,13h ;mode number from 0-19
INT 10h

19. Source Code for Writing Pixel
Code to write pixel using video BIOS interrupt 10h and service number 0ch.
MOV AH,0Ch
MOV AL,COLOR_NUM
MOV BH,0
MOV CX,ROW_NUM
MOV DX,COLUMN_NUM
INT 10h

20. Incremental Line Algorithm
This algorithm exploits simple line equation
y = m x + b
where m = dy / dx
and b = y – m x

21. DDA Algorithm
DDA abbreviated for digital differential analyzer has a very simple technique.
Find difference, dx and dy as:
dy = y2 – y1
dx = x2 – x1

22. if |dx| > |dy| then
step = |dx|
else
step = |dy|
Now very simple to say that step is the total number of pixels required for a line.

23. Next step is to find xIncrement and yIncrement:
xIncrement = dx/step
yIncrement = dy/step

25. Circle Drawing Using Cartesian Coordinates
This technique uses the equation for a circle with radius r centered at (0,0):
x2 + y2 = r2,
an obvious choice is to plot
y = ± r2 - x2
against different values of x.

26. Polar Coordinates Algorithm
Circle2 (xcenter, ycenter, radius)
for  = 0 to 2 step 1/r
x = xc + r * cos 
y = yc + r * sin 
drawPixel (x, y)

27. Eight Octants Symmetry

28. Midpoint Circle Algorithmk
X2+Y2-R2=0 k
Xk+1 k

29. Rotation Y X 1 2 3 4 5 6 7 8 9 10

30. Scaling Y X 1 2 3 4 5 6 7 8 9 10

31. Basic Transformations
Rotation
Scaling

32. Video Controller
Architecture of a raster system with a fixed portion of system memory reserved for the frame buffer.

33. Color CRT Monitors
Beam Penetration Method
Shadow Mask Method

34. Translation
tx = 2
ty = 3 Y X 1 2 3 4 5 6 7 8 9 10

35. Color CRT Monitors
Beam Penetration Method
Shadow Mask Method