11. RM [1]-11
Graphics: Main Components
Theory
Analytical Geometry
Vectors and Matrices
Algorithms
Eg: Line drawing, Filling etc.
Implementation
Programming (OpenGL)
12. RM [1]-12
Graphics Hardware
Line Drawing Devices:
Eg. Pen Plotters
Advantages: Perfect lines, Sharp Diagrams
Disadvantages: Not suitable for filled regions.
13. RM [1]-13
Graphics Hardware
Raster Devices: Create pictures by displaying
dots
Eg: Video monitor, dot-matrix printer, laser
printer, ink-jet printer, film recorder
Advantages: Filled, shaded regions are easily
displayed
Disadvantages: Jaggies
Pixel
14. RM [1]-14
Pixel Depth
Pixel depth refers to the number of bits used
to represent a pixel value.
1 bit/pixel: 0
1
2 Levels
(Bi-level image)
2 bits/pixel: 0
0
4 Levels
0
1
1 0
1 1
15. RM [1]-15
Pixel Depth
1 bit per pixel produce 2 levels (bi-
level image).
2 bits per pixel produce 4 levels.
8 bits per pixel produce 256 levels.
In general, if the pixel depth is n, then
it is possible to have 2n levels.
16. RM [1]-16
Raster Display
Most display used for computer graphics nowadays
are raster displays.
Image presented in display surface that contains
certain number of pixels. Eg. 480 x 640 (r x c).
Frame buffer is a region of memory sufficiently large to
hold all the pixel values for display.
17. RM [1]-17
Frame Buffer
System with 64 color (3 DACs):
Each DAC uses 2 bits/pixel.
Total color: 4 x 4 x 4 = 64
If the display surface is 1024 x 1280, then the
memory required for frame buffer is 0.9375 MB
Monochrome Video display:
Only one DAC required. 6 planes of memory in frame
buffer gives 26 = 64 level of gray.
18. RM [1]-18
Frame Buffer
System with 24 bit color (3 DACs):
Each DAC uses 8 bits/pixel. (Total 24 bits/pixel)
Total color: 28 x 28 x 28 = 224
If the display surface is 1024 x 1280, then the memory
required for frame buffer is 3.75MB
19. RM
Basis colors: R, G, B
R: Red=[1, 0, 0]
G: Green=[0, 1, 0]
B: Blue=[0, 0, 1]
C: Cyan=[0, 1, 1]
M: Magenta=[1, 0, 1]
Y:Yellow=[1, 1, 0]
W:White=[1,1,1]
K: Black=[0,0,0]
Color Models: RGB Diagram
• RGB Model is used for colored light sources
• RGB Model is additive
20. RM [1]-20
Complementary Colors: Two colors that combine to form
White. Eg. Red, Cyan.
Gray Values: Every point on the primary diagonal has equal
values for all the components.
Color Models: RGB Cube
21. RM [1]-21
Basis colors: C, M, Y
C: Cyan=[1, 0, 0]
M: Magenta=[0, 1, 0]
Y: Yellow=[0, 0, 1]
R: Red=[0, 1, 1]
G: Green=[1, 0, 1]
B: Blue=[1, 1, 0]
W:White=[0,0,0]
K: Black=[1,1,1]
Color Models: CMY Diagram
• CMY Model is used for colored pigments
• CMY Model is subtractive
22. RM [1]-22
Color Models: RGB <-> CMY
(r, g, b)RGB = (1,1,1) (c, m, y)CMY
Light
A red colored surface
absorbs cyan from a
white light
24. RM [1]-24
H (Hue): 0 to 360 degrees 0: Red, 60: Yellow ….
S (Saturation): 0 to 1 0: Axis, 1: Boundary
V (Value): 0 to 1 0: Vertex, 1: Base
Examples:
Eg. Yellow: [60, 1.0, 1.0]
Black: [ -, -, 0.0]
White: [-, 0.0, 1.0]
Color Models: HSV
25. RM [1]-25
RGB Color Definition (OpenGL)
Set a particular color: glColor3f(r,g,b);
Set a background color: glClearColor(r,g,b,1);
Clear the window to background color:
glClear(GL_COLOR_BUFFER_BIT);
![RM [1]-2
Books
•F.S. Hill, Computer Graphics Using
OpenGL, Prentice-Hall (2001).
•Mason Woo, OpenGL Programming
Guide, Addison Wesley (2000).
•Hearn and Baker, Computer Graphics,
Prentice-Hall (1997).](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)