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Main components of graphical systems Graphical devices Colors

Main components of graphical systems Graphical devices Colors. Graphical system: main components. Input Devices. Mouse and trackball. Input Devices. Joystick. Input Devices. Tablet and pen. Input Devices. Light pen and touch screen. Input Devices. Space ball and data glove (3D data).

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Main components of graphical systems Graphical devices Colors

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  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.

  23. 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.

  24. 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.

  25. 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.

  26. Colors • RGB model

  27. Colors • RGB Color cube

  28. Colors • CMY model

  29. Colors • CMY cube

  30. 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

  31. 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)

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

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

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

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

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

  37. Color palette • Color table (palette)

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