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Computer Graphics in Java

Computer Graphics in Java. CR325. Graphics standard. WMF commands. WMF commands. Font test - serif. Graphics2D standard. uniform scale. WMFGraphics2D. dialog font transform. WMFGraphics extra. rotated sansserif. What is Computer Graphics?. A kind of Data processing

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Computer Graphics in Java

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  1. Computer Graphics in Java CR325

  2. Graphics standard WMF commands WMF commands Font test - serif Graphics2D standard uniform scale WMFGraphics2D dialog font transform WMFGraphics extra rotated sansserif

  3. 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.

  4. What do we study in CG?? methods for digitally synthesizing and manipulating visual content

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

  7. 2D Computer Graphics • Synthesis of images—from two-dimensional models Two kinds of 2D Computer Graphics Raster and Vector

  8. Raster Graphics • image (array of pixels).

  9. Vector Graphics • geometrical primitives (e.g., points, lines, curves, and shapes or polygon(s)), to represent images

  10. 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).

  11. Graphics Systems Five major elements - processor, memory, frame buffer, output devices, input devices

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

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

  14. Output Devices The cathode-ray tube CRT

  15. Output Devices RGB – shadow mask

  16. 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?

  17. Trading an eye for an ear

  18. Human Visual System - HVS • rods and cones excited by electromagnetic energy in the range 350-780 nm • sizes of rods and cones determines the resolution of HVS – our visual acuity • the sensors in the human eye do not react uniformly to the light energy at different wavelengths

  19. Human Visual System - HVS Courtesy of http://www.webvision.med.utah.edu/into.html

  20. Human Visual System • different HVS response for single frequency light – red/green/blue • relative brightness response at different frequencies • this curve is known as Commision Internationale de L’Eclairage (CIE) standard observer curve • the curve matches the sensitivity of the monochromatic sensors used in black&white films and video camera • most sensitive to GREEN colors

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

  22. Human Visual System • three different cones in HVS • blue, green & yellow – often reported as red for compatibility with camera & film

  23. 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

  24. 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

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

  26. 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

  27. 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.

  28. Pixels and Frame Buffer Most graphics systems are pixel based – need of rasterization or scan conversion; pixel = picture element8 bits deep frame – 256 colors; 24 or 32 bits for RGB colors picture detail

  29. 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!

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

  31. 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.

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

  33. Quantization Error is visible

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

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

  36. 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;

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

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

  39. 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)

  40. 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

  41. 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

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

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

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

  45. 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

  46. 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

  47. 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.

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

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