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Computer graphic basics

Computer graphic basics. by Alessandro Cazziolato. Putting images into computer memory. ?. 1010010011 0011110101 0111101111 1110001011. In the computer memory you can store only numbers. Solving the problem. 11110000. 00111100. 00001111. We must transform colors in numbers.

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Computer graphic basics

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  1. Computer graphic basics by Alessandro Cazziolato

  2. Putting images intocomputer memory ? 1010010011001111010101111011111110001011 In the computer memory you can storeonly numbers

  3. Solving the problem 11110000 00111100 00001111 We must transform colors in numbers

  4. Coding an information LLL LLL • An “O” can’t travel across an electrical wire • … but an electrical impulse can! • By convention we state that “O” is coded into 3 long pulse _ _ _ O is _ _ _ _ _ _ is an O

  5. Color models • A color model is a mathematical model describing the way colors can be represented as tuples of numbers • It is also a system for creating a huge range of colors from a small set of basic or primary colors • The two most common color models used in computer graphics are RGB and CMYK

  6. RGB color model • 3 primary colors: Red, Green and Blue • Uses light to display color • It is an additive color model • For computer displays

  7. CMYK color model • 3 primary colors (plus one): Cyan, Magenta and Yellow (plus Black) • Uses ink to display color • Black is added to compensate for ink impurities • It is a subtractive color model • For printed material

  8. Color spaces • A color space is a particular variant of a color model with a specific range of colors • This range of colors is called gamut

  9. Pixel From images to pixels • We divide the image in a large amount of small parts • Each part has it’s own single color • A single part is a basic element of the picture, and is called Pixel

  10. Bit depth • The bit depth is the number of bits used to store information about the color of each pixel of an image • The higher the depth, the more colors are available

  11. Bit depth: 1bit • Black and white images • 1bit = 2 colors • 21 = 2

  12. Bit depth: 8bit (grayscale) • Grayscale images • 8bit = 256 colors • 28 = 256

  13. Bit depth: 8bit (color palette) • Color images with color palette • 8bit = 256 colors • 28 = 256

  14. Bit depth: 24bit (true color) • Color images (no palette) • 24bit = 16,777,216 colors • 224 = 16,777,216 • The human eye can see about 10 to 15 millions of colors • 24 bit depth is true color

  15. Coding Color model Color space Primary color RGB CMYK Gamut Bit depth Black & white Grayscale Color palette True color Glossary

  16. Colors Size Resolution Image quality Image quality pixels bit depth dpi & ppi Screen & printer

  17. Final reports • Has Internet a graphics standard “best choise”? • Why? • bit depth • pixels • dpi & ppi when and why?

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