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Transcript

  • 1. How computers represent graphics
  • 2. Graphics An 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
  • 3. Graphics Packages Graphics packages can be classed as either: Bitmapped graphics (painting) Vector graphics (drawing)
  • 4. Bitmapped Graphics The 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
  • 5. Bitmapped Graphics In 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
  • 6. Bitmapped Graphics How many colours could be represented using 3 bits ?
  • 7. Bitmapped Graphics How many colours could be represented using 3 bits ? 000 001 010 011 100 101 110 111 8 colours ( 2 3 ) could be represented using 3 bits
  • 8. Bit Depth The 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)
  • 9. Credits
    • CfE 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)