How computers representHow computers representgraphicsgraphics
GraphicsAn image is made up of tiny dots called pixels.
The resolution determines the quality of the picture. The smaller the pixels the finer the detail that can be displayed on the screen.
High Resolution Image Low Resolution Image
Graphics PackagesGraphics packages can be classed as either:
Bitmapped graphics (painting) Vector graphics (drawing)
Bitmapped GraphicsThe image is saved in a two dimensional array using binary numbers to represent the colours in the pixels. Each pixel is represented by the same number of bits.
In this example, two colours have been used (black/white) and so each pixel is represented by one bit.
0 = white, 1 = black
Bitmapped GraphicsIn this example, four colours are used in the graphic and so each pixel is represented using two bits.
00 = white, 01 = blue, 10 = red, 11 = black
Bitmapped GraphicsHow many colours could be represented using 3 bits?
Bitmapped GraphicsHow many colours could be represented using 3 bits?
000
001
010
011
100
101
110
111
8 colours (23) could be represented using 3 bits
Bit DepthThe number of bits used to represent the colour of the pixels is called the bit depth.
Colours Bits
2 1
4 2
8 3
16 4
32 5
64 6
128 7
256 8
65536 16
16777216 24 (True Colour)
CreditsCfE Computing – How computers represent graphics
Produced by P. Greene and adapted by R. G. Simpson for the City of Edinburgh Council 2004
Adapted by M. Cunningham 2011
All images licenced under Creative Commons 3.0• Sets of blue waves and surfing boards by Horia Varlan (Flickr)• Black & White Atlanta skyline by Glen Edelson (Flickr)• A Cactus Flower for Capt. Suresh by Koshy Koshy (Flickr)• Sunset over the Danube - Budapest by joiseyshowaa (Flickr)• Edinburgh skyline by rovingI (Flickr)
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