Main components of graphical systems Graphical devices Colors

1. Main components of graphical systems Graphical devices Colors

2. Graphical system: main components

3. Input Devices • Mouse and trackball

4. Input Devices • Joystick

5. Input Devices • Tablet and pen

6. Input Devices • Light pen and touch screen

7. Input Devices • Space ball and data glove (3D data)

8. Input Devices • Scanner, digital camera, camcorder

9. Input Devices • 3D scanner

10. Output Devices • Plotter

11. Output Devices • Plotter

12. Output Devices • CRT (cathode Ray Tube)

13. Output Devices • CRT

14. Output Devices • Raster Scan • Refresh at least 24 frames/s

15. Output Devices • Color CRT /cathode-ray tube/

16. Output Devices • Color CRT

17. Output Devices • Color CRT

18. Output Devices • LCD (Liquid Crystal Display)

19. Output Devices • Plasma panels

20. Output Devices • Ink-jet and laser printers

21. Output Devices • Calligraphic (vector) screens

22. Colors • It is difficult to explain colors: they should be experienced. • Color is nothing more that wavelengths of light at a certain frequency. • Actually, the human eye is only said to perceive a small fraction of the total light available. • Certain lights called Gamma Rays, X-rays, and Ultraviolet lights are too low of a frequency for humans to see. • Lights like Infrared, Microwaves, and Radio waves, are too high of a frequency for the human eye to see. • Humans only see a small portion of light between these frequencies and we calls these lights color.

24. Colors • The color of an object is evident by the amount of light it reflects. • For example, a red apple reflects mostly red light, and absorbs mostly all other colors. • The color white is obtained when all colors are reflected off an object (no colors absorbed) giving the object appearance of white. • Black is the absorption of all colors. It is not considered as a color. • Black is considered the absence of color, and therefore is not allowed to join its color family.

25. Color models: RGB Model • There are different ways to choose color for your drawing. • The easiest and most powerful way is to use RGB color. • RGB color stands for Red, Green, and Blue, and is called additive color. • It is given this name because RGB starts with the absence of color, and then adds elements of red, green, and blue to achieve the desired color.

26. RGB Model • It is not possible to obtain all colors with RGB model, or with any other color model. RGB just matches a color as close as possible. • Usually there are 256 different values for each red, green, and blue. This also means that there are about 16.7 million different colors available (256*256*256 = 28 * 28 * 28). • Some systems and languages, such as OpenGL, uses a similar idea with RGB color, except that they may use numbers from 0.0 to 1.0. • Theoretically this means that there is an infinite amount of colors formed from RGB because there is an infinite amount of numbers between 0 and 1.

27. Colors • RGB model

28. Colors • RGB Color cube

29. Colors • CMY model

30. Colors • CMY cube

31. Colors • HSV model (hue, saturation, value): used by artists • or HSL model (L-light) • Hue: the name that we give to a color: red, yellow, cyan, etc. • Saturation: “how pure the color is”, that is how far is a hue from the same hue mixed with white so that the color has more pastel shade • Value/Light - how bright the color appear

32. Model • H - hue, S – saturation and I - intensity r = R / (R + B + G); b = B / (R + B + G); g = G / (R + B + G), S = 1 - 3 min (r, g, b)

33. Colors • HSV model (hue, saturation, value)

34. Levels of Gray • Levels of gray/colors: instead of 0/1 more digits

35. Levels of Gray • Reducing the levels of gray: Original scanned picture

36. Levels of Gray • Reducing the levels of gray: Three bits per pixel

37. Levels of Gray • Reducing the levels of gray: One bit per pixel

38. Color palette • Color table (palette)