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Raster graphics. Colour depth 01 1 bit pr pixel = 2 combinations (2 1 ): 2 bits pr pixel = 4 combinations (2 2 ): 00011011 4 bits pr pixel = 16 combinations(2.

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Presentation on theme: "Raster graphics. Colour depth 01 1 bit pr pixel = 2 combinations (2 1 ): 2 bits pr pixel = 4 combinations (2 2 ): 00011011 4 bits pr pixel = 16 combinations(2."— Presentation transcript:

1 Raster graphics

2

3 Colour depth 01 1 bit pr pixel = 2 combinations (2 1 ): 2 bits pr pixel = 4 combinations (2 2 ): bits pr pixel = 16 combinations(2 4 ) 8 bits pr pixel = 256 combinations(2 8 ) 16 bits pr pixel = combinations(2 16 ) 24 bits pr pixel = combinations(2 24 )

4 Colour depth 1 bpp= 2 1 = 2 colours 2 bpp= 2 2 = 4 colours 4 bpp= 2 4 = 16 colours 8 bpp= 2 8 = 256 colours 16 bpp= 2 16 = colours 24 bpp= 2 24 = colours

5 Colour depth

6 File sizes 100 x 100 pixels in 1 bit (2 c.): 100 x 100 x 1 / 8 = 1250 bytes = 1,25 Kb 100 x 100 pixels in 8 bit (256 c.): 100 x 100 x 8 / 8 = bytes = 10,0 Kb 100 x 100 pixels in 24 bit ( c.): 100 x 100 x 24 / 8 = bytes = 30,0 Kb

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

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

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

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

11 Jpg compression 766 x 782 pixels, 24 bit TIF no compression 1720 KB 766 x 782 pixels, 24 bit JPG compression KB

12 Jpg compression Compression factor x200 pixels, 24 bit Kompression x200 pixels, 24 bit Kompression 99 11,5 kb1,7 kb

13 Jpg / gif …photos jpg, 11,5 kbgif, 22,4 kb 200x250 pixels

14 Jpg / gif …drawing gif, 6,08 kb jpg, 5,5 kb

15 Anti aliasing

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

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

18 Digitalization Digital camera CCD chipLens light Data for Memory

19 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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