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Raster graphics

Raster graphics. Raster graphics. 1 bit pr pixel = 2 combinations (2 1 ):. 0. 1. 2 bits pr pixel = 4 combinations (2 2 ):. 00. 01. 10. 11. Colour depth. 4 bits pr pixel = 16 combinations(2 4 ) 8 bits pr pixel = 256 combinations(2 8 ) 16 bits pr pixel = 65636 combinations(2 16 )

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Raster graphics

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  1. Raster graphics

  2. Raster graphics

  3. 1 bit pr pixel = 2 combinations (21): 0 1 2 bits pr pixel = 4 combinations (22): 00 01 10 11 Colour depth 4 bits pr pixel = 16 combinations(24) 8 bits pr pixel = 256 combinations(28) 16 bits pr pixel = 65636 combinations(216) 24 bits pr pixel =16777216 combinations(224)

  4. Colour depth 1 bpp = 21 = 2 colours 2 bpp = 22 = 4 colours 4 bpp = 24 = 16 colours 8 bpp = 28 = 256 colours 16 bpp = 216 = 65.536 colours 24 bpp = 224 = 16.777.216 colours

  5. Colour depth

  6. Filfe formats F.ex: • TIF (Tagged Image File Format) 1-32 bit • BMP (Windows Bitmap) 8-24 bit • TGA (Targa) 24-32 bit • JPG (JPEG – Joint Photographics Expert Group) 8-24 bit • GIF (Graphics Interchange Format) 1-8 bit • PNG (Portable Network Graphics) 4-24 bit

  7. Gif-format • Max 256 colours • Good for logos, line drawings, buttons • May be transparent • May be animated • Use LZW compression

  8. Optimized palette Screen set to more than 256 colours Gif-format palette System palette Goes on 256-colours screens. ‘Uses ‘dithering’

  9. Jpg-formatet • 24 bits colour depth, ie 16.7 million colours(or 8-bit grey scale) • Good for photos • Extreme compression possible

  10. 766 x 782 pixels, 24 bit TIF no compression 1720 KB 766 x 782 pixels, 24 bit JPG compression 25 104 KB Jpg compression

  11. Jpg compression • Compression factor 1-99 250x200 pixels, 24 bit Kompression 15 250x200 pixels, 24 bit Kompression 99 11,5 kb 1,7 kb

  12. Jpg / gif …photos 200x250pixels 200x250pixels jpg, 11,5 kb gif, 22,4 kb

  13. Jpg / gif …drawing gif, 6,08 kb jpg, 5,5 kb

  14. Anti aliasing

  15. Digitalization (f.x. Scanning) Digitalization Analog (photo) Digital (Raster image)

  16. Image Lamp Direction of scan Photo cells Scanner head Data for computer Digitalization Flatbed scanner

  17. Digitalization Lens CCD chip light Data for Memory Digital camera

  18. Scanning - DPI • DPI = Dots Per Inch – • Computer screen = 72 DPI • 10x10 cm output = 288 x 288 pixels (72 / 2,5 x 10) • Standard laser print = 600 DPI • 10x10 cm output = 2400 x 2400 pixels (600 / 2,5 x 10)

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