People cant see more than 64 levels of gray use 6

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People can’t see more than 64 levels of gray Use 6 bits instead of 8 (25%) People don’t see color as well as B/W Use 6 bits for B/W and much less for color
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Coherence If we know the previous value of something, then we generally have a good idea what the next value will be 3 Techniques Run length encoding Reuse of subsequences Prediction and error
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Run length encoding Values are frequently repeated. Instead of storing each value, store a single value with a count of how many times to repeat
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12 x 10 = 120 pixels 120 pixels x 3 bytes/pixel = 360 bytes 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 10 11
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Run encoded 12 6 4 1 9 1 9 1 9 1 3 6 1 9 1 9 1 9 1 9 1 5 12 RGB - 3 bytes Count - 1 byte Entries - 23 Space - 4*23 = 92 Compression (360-92)/360 = 74% 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 10 11
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Run encoded - with indexed color 12 6 4 1 9 1 9 1 9 1 3 6 1 9 1 9 1 9 1 9 1 5 12 4 colors - 12 bytes index - 2 bits Count - 6 bits Entries - 23 Space - 12+1*23 = 35 Compression (360-35)/360 = 90% 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 10 11
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Run encoding HELLO Works well
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Run encoding Works Badly
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Run encoding Works well
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Run encoding Not good Too much variation in the rose
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Run encoding - text four score and seven years ago, our fathers brought forth on this continent Not good no repetition
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Run Encoding - Audio Not good No repetition
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Run Encoding - Audio Not good No repetition
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Reuse common sequences 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 10 11
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Reuse common sequences 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 10 11
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Reuse common sequences 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 10 11
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Reuse common sequences 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 10 11
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Reuse common sequences
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Reuse common sequences
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Reuse common sequences
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  • Winter '08
  • Morse,B
  • Reuse common sequences

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