Fluency with IT

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HSV colour model
Primary colours Red Green Blue Secondary Cyan Mag
enta Yellow SecondaryWhite-Primary (create
colors for print)
Source http//www.ncsu.edu/scivis/lessons/colormo
dels/color_models2.html
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HSV colour model, tertiary colours
Add the colours between primary and secondary
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HSV colour model

• Colour specified by 3 parameters
• hue (angle on disc)
• saturation (how dominant is the hue relative to
  the other colours)
• value (overall intensity of the light)

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HSV colour model
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• Colour sensation. It is determined by
• Light
• Physiology
• Psychology

Experiment
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Read the colors of the words in col 1, then col
3, then col 2
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Experiments with optical illusions
http//www.michaelbach.de/ot/col_lilacChaser/index
.html
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Capturing images (with digital camera)
Image area (exposed to light)
Parallel (vertical) registers
Pixel
Serial (horizontal) register
Output amplifier
masked area (not exposed to light)
(slides by Claudio Cumani, European Southern
Observatory)
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• Representing the intensity of a primary color
  (eg. Red)
• left 3 bits per color (numbers 0 to 7)
• right 8 bits per color (numbers 0 to 255)

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• Lossless compression
• original x by y pixels
• stored the color of every pixel, row by row

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• Lossless compression
• original x by y pixels
• stored the color of every pixel, row by row
• A lot of black pixels!
• (R,G,B0,0,0)
• Replace sequence of black pixels by 2 numbers
• 0, n
• n - nr repetitions.

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Image from a digital camera (10MB) stored as 128kB
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8x8 blocks of pixels
JPEG compression
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• lt- 1 block.

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We can store the average value for every block
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What if we stored the average for 4x4 blocks?