digital image processing in the name of god digital image processing lecture6: color image...
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In The Name Of God
Digital Image ProcessingDigital Image Processing
Lecture6:
Color Image Processing
By: M. Ghelich OghliM. Ghelich OghliE-mail: E-mail: [email protected][email protected]
Fall 2012
Visible Spectrum
Lighting conditions
Image taken lit by a flash.
Image taken lit by a tungsten lamp.
• The lighting conditions of the scene have a large effect on the colours recorded.
Color Representation
Indexed Images
Color characteristic
Hue : An attribute associated with the dominant Wavelength( or dominant color perceived by an observer)
Saturation: refers to relative purity or amount of white light mixed with hue( colors such as pink (red and white) are less saturated)
Hue & Saturation --> chromaticity
Brightness: chromatic notion of intensity
Color Models
RGB Color Model (space or system): each color appears in its primary components of red green and blue.
RGB Color Space
CMY and CMYK Color Model
Cyan Magenta and yellow color (secondary colors) is used to represent colors
Used mostly in printing devices
for better printing of black color, this color may be added to the system (CMYK system)
CMYK Model Converting CMYK to RGB
Converting RGB to CMYK(semi-equivalent(
HSI Color Model
HSI Color Model
HSI Color Model
Color Transformation
• YCbCr (used in MPEG video)
Other Color Spaces
• YUV( used in PAL TV systems)
Color Image Processing
• Full color processing: the images in question typically are acquired with full color sensor
• Pseudo-color processing: assigning a color to a particular monochrome intensity or range of intensities.
Pseudocolor Image processing
Also Called false Image processing Definition: is the process of assigning color to monochrome
image Advantage: Human can discern thousands of colors compared to
one or two dozen shades of gray. Method: Intensity Slicing
Intensity Slicing
Intensity Slicing Single level slicing( X-ray Weld image)
Intensity Slicing Multi level slicing( radiation image)
Intensity Slicing
Gray Level to color Transformation
Basics of Full color Image Processing
• Per-color-component based processing: each color is processed individually and then is combined to obtain processed image
• Vector based processing: each color pixel is interpreted as vector and processed individually .
Basics of Full color Image Processing
Color Transformation
Gray level transformation
Color transformation
Color Transformation
Color Complement
Color Complement
Tone and Color Correction
Tone Correction: adjusting brightness and contrast of the image experimentally
methods
1- changing I in HSI model
2- mapping all colors of RGB or CMYK space with the same transformation
Tone correction
Color Correction
Color Image Smoothing
Color Image Smoothing
Color Image Smoothing
Color Image Smoothing
Color Image Laplacian
Color Image Laplacian