Sheng-Fang Huang

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Digital Image Processing

• Sheng-Fang Huang
• Chapter 6

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6.1 Color Fundamentals
White light consists of a continuous spectrum of
colors ranging from violet to red.
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Color Spectrum
Visible light is composed of a relatively narrow
band of frequencies in the electromagnetic
spectrum.
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Color Fundamentals

• The colors that humans perceive of an object are
  determined by the nature of the light reflected
  from the object.
• Green objects reflect light with wavelengths in
  the 500 to 570 nm, and absorb those at other
  wavelengths.
• The light is visible to human eyes if its
  wavelength is between 380-780 (nm).
• If the light is achromatic, its only attribute is
  intensity.
• The term gray level refers to a scalar ranging
  from black to white.

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Color Fundamentals

• The cone cells in human eye can be divided into
  three categories, corresponding roughly to red,
  green and blue (Figure 6.3).
• Due to these characteristics of the human eye,
  colors are seen as variable combinations of the
  primary colors red (700 nm), green (546.1 nm),
  and blue (435.8 nm).
• Standardized in 1931.
• This standardization does not mean these three
  primary colors can generate all spectrum colors.

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Secondary Colors

• The primary colors can be added to produce the
  secondary colors of light Cyan (??), Magenta
  (??),Yellow (?).

• The primary colors of pigments are cyan, magenta,
  and yellow, while the secondary colors are red,
  green, and blue.

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Color Fundamentals

• The characteristics generally used to distinguish
  one color from another are hue, saturation, and
  brightness.