Computer Graphics in Java

1. Computer Graphics in Java CR325

2. What is Computer Graphics? • A kind of Data processing • Voice and Signal Processing = 1D data processing • Image Processing = 2D data processing • Computer Graphics = 3D data in with 2D data out. Geometry is transformed into images.

3. What is Computer Animation? • Like Computer Graphics with a difference. • Animation=movement. This is simulated with image sequences. Output is an image sequence. Input is 3D geometry.

4. Why study Computer Graphics? • Entertainment • Visualization of data (analysis) • Simulation can be visualized with CG. • CAD (Computer Aided Design)

5. What do people study in CG? • How to do 2D drawing • How to draw a line • How to draw a circle, etc. • How to do 3D drawing • How to draw a 3D line • How to draw a sphere, etc.

6. Where do we get input? • Pick device • Gives us a location • Mouse, light-pen, arrow-keys, keyboard, • Joystick, tablet, scanner, image • video camera with a cooperative target. • Geometries • Dynamics, kinematics (math).

7. Introduction to 2D Graphics • Draw some 2D geometries. • Input is 2D geometry • Ouput is image.

8. How do we represent an image? • Image Processing answer: 2D array of pixels • Computer Answer: BREP:vectors • to the right is a bitmap • vector vs. bitmap

9. What is an image? • A 2D array of PIXELS.

10. What is a PIXEL • A picture element. • Typically a pixel can be described as an intensity for light at a given location. • Location (200,20), I = 255; // gray scale • Location (34,50), R=255, G= 0, B =0; //red pixel. • Looks like a dot!

11. What is an Image? • a 2D array of pixels • a pixel is a scalar quantity that represents the intensity of light. It smallest area within the given image.

12. How do we represent a pixel? • how do we represent light?

13. Trading an eye for an ear

14. Spectra of the Human Visual System • ranges from 400 nm wavelength to about 800 nm, 1 nm = 10 ** -9 meters • d = rate * time • rate = c = 3 * 10 ** 8 meters / second • d = wavelength = 400 * 10 **-9 meters • T = lambda/c, f = 1/T = c / lambda • f = 3 * 10 ^ 8 / 4 * 10 ^ -7 =750.*10^12?

15. An eye is a Multi-mega pixel camera • It has a lens (adjustable zoom) • It has an automatic f-stop (iris 2-8 mm) • It has a sensor plane (100 million pixels) • The sensor has a transfer function senstive to mesopic range; 380 to about 700 nm

16. The eyes have a USB2 data rate! • 250,000 neurons in the optic nerve • variable voltage output on EACH nerve • 17.5 million neural samples per second • 12.8 bits per sample • 224 Mbps, per eye (a 1/2 G bps system!). • Compression using lateral inhibition between the retinal neurons

17. Response curves • Eye has Gaussian response to light. • Gives rise to biologically motivated image processing

18. Quantization of an Image • Computers use digital cameras -> quantization

19. Quantization Error is visible

20. Displays • Color Monitors are made for people • physiological arguments are used for display design

21. What is light? • any electromagnetic energy • visible light is typically visible to the human visual system (eye).

22. How do we represent a pixel • assume that the pixel is for humans. • You need to know the dynamic range of the eye! • 1 part in a million is needed for a pixel that displays on a monitor for people. • Typically we use 24 bits per pixel, 8 bits per color.

23. peter packed a pickled pixelits color was that of hash.And every system that displayed it would crash!

24. Displays are designed for • human visual system (eye) • Painting with LIGHT (additive synthesis) display • This is not painting with MUD! (subtractive synthesis) printer

25. Overview publicint filterRGB (int rgb) { int r = (rgb & 0xff0000) >>16; int g = (rgb & 0xff00) >> 8; int b = rgb & 0xff; int gr = (r + g + b) / 3; int p = 0xff000000 | (gr << 16) | (gr << 8) | gr; return p // p = 0xffgrgrgr;

26. How would do you pack RGB? • int pack(int r, int g, int b) { return 0xff000000 | (r << 16) | (g << 8) | b; • }

27. How do I represent the following in decimal • int I = 1; • int k = ~I+1; • how much is k? Ans: -1

28. Intro to bitwise ops • and - & - bitwise (not && is logical) • or - | - bitwise (not || is logical) • not - ~ - bitwise (not !, is logical) • xor - ^ - bitwise (has no logical correspondence)

29. Intro to ANDing • int I = 0; • int j = 1; • I&I is 0 • I&J is 0 • J&I is 0 • J&J is 1

30. Intro to Oring • int i=0xF0; S={0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f} • int j =0x0F; • i|I is 240 = 0xF0 • i|j is 255 in decimal = 0xFF • 0xF0 = (in base 2) 11110000 • 0x0F = (in base 2) 00001111 • 0x0F | 0xF0 = 11111111

31. Using hex for ANDing • int i=0x7a; • int j =0x0F; • how much is i&j ? • 01111100 & • 00001111 = • 00001100 = 0x0c

32. using hex for not • int i=0x7a; • int j =0x0F; • how much is ~j? 0xfffffff0 nibble is 4 bits, byte is 8 bits

33. using hex for xor • int i=0x7a; • int j =0x0F; • how much is i^j? • 01111100 = I^ • 00001111 = j • 01110011 = i^j = 0x73

34. Common Radicies • in java, you can use: • binary (base 2) Radix 2 • octal (base 8) Radix 8 • decimal (base 10) Radix 10 • hexidecimal (base 16) Radix 16

35. How come they call it base 2? • You can only have 0 and 1, so why call it base 2? • Why not call it base 1? • Cardinality of the set of symbols is the radix S = {0, 1}, card(s)=2

36. Why call it a base? • The base of the exponent! • 1101, base 2 is, in decimal • 1*2^3 + 1 * 2^2 + 0 * 2 ^ 1 + 1 • = 8 + 4 + 0 + 1 = 13 base 10. • This is called positional notation.

37. Doing the positional notation in hex • 0x28 = 2 * 16 ^ 1 + 8 * 16 ^ 0 • = 2 * 16 + 8 • = 32 + 8 = 40 base 10