Color Image Processing
Digital Image Processing
Chapter 6: Color Image Processing
Spectrum of White Light
1666 Sir Isaac Newton, 24 year old, discovered white light spectrum.
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
Electromagnetic Spectrum
Visible light wavelength: from around 400 to 700 nm 1. For an achromatic (monochrome) light source, there is only 1 attribute to describe the quality: intensity 2. For a chromatic light source, there are 3 attributes to describe the quality: Radiance = total amount of energy flow from a light source (Watts) Luminance = amount of energy received by an observer (lumens) Brightness = intensity
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
Cross section illustration
The Eye
UMCP ENEE631 Slides (created by M.Wu © 2004)
Figure is from slides at Gonzalez/ Woods DIP book website (Chapter 2)
Two Types of Photoreceptors at Retina
• Rods
– – – – – – – – – Long and thin Large quantity (~ 100 million) Provide scotopic vision (i.e., dim light vision or at low illumination) Only extract luminance information and provide a general overall picture Short and thick, densely packed in fovea (center of retina) Much fewer (~ 6.5 million) and less sensitive to light than rods Provide photopic vision (i.e., bright light vision or at high illumination) Help resolve fine details as each cone is connected to its own nerve end Responsible for color vision our interest (well-lighted display)
• Cones
– Mesopic vision
• provided at intermediate illumination by both rod and cones
Sensitivity of Cones in the Human Eye
6-7 millions cones in a human eye - 65% sensitive to Red light - 33% sensitive to Green light - 2 % sensitive to Blue light
Primary colors: Defined CIE in 1931 Red = 700 nm Green = 546.1nm Blue = 435.8 nm CIE = Commission Internationale de l’Eclairage (The International Commission on Illumination)
(Images from Rafael
Chapter 6: Color Image Processing
Spectrum of White Light
1666 Sir Isaac Newton, 24 year old, discovered white light spectrum.
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
Electromagnetic Spectrum
Visible light wavelength: from around 400 to 700 nm 1. For an achromatic (monochrome) light source, there is only 1 attribute to describe the quality: intensity 2. For a chromatic light source, there are 3 attributes to describe the quality: Radiance = total amount of energy flow from a light source (Watts) Luminance = amount of energy received by an observer (lumens) Brightness = intensity
(Images from Rafael C. Gonzalez and Richard E. Wood, Digital Image Processing, 2nd Edition.
Cross section illustration
The Eye
UMCP ENEE631 Slides (created by M.Wu © 2004)
Figure is from slides at Gonzalez/ Woods DIP book website (Chapter 2)
Two Types of Photoreceptors at Retina
• Rods
– – – – – – – – – Long and thin Large quantity (~ 100 million) Provide scotopic vision (i.e., dim light vision or at low illumination) Only extract luminance information and provide a general overall picture Short and thick, densely packed in fovea (center of retina) Much fewer (~ 6.5 million) and less sensitive to light than rods Provide photopic vision (i.e., bright light vision or at high illumination) Help resolve fine details as each cone is connected to its own nerve end Responsible for color vision our interest (well-lighted display)
• Cones
– Mesopic vision
• provided at intermediate illumination by both rod and cones
Sensitivity of Cones in the Human Eye
6-7 millions cones in a human eye - 65% sensitive to Red light - 33% sensitive to Green light - 2 % sensitive to Blue light
Primary colors: Defined CIE in 1931 Red = 700 nm Green = 546.1nm Blue = 435.8 nm CIE = Commission Internationale de l’Eclairage (The International Commission on Illumination)
(Images from Rafael