1 Vladimir Botchko [email protected] Lecture 5. Color Image Processing Lappeenranta University of Technology (Finland)

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Vladimir Botchko [email protected]

Lecture 5. Color Image ProcessingLecture 5. Color Image Processing

Lappeenranta University of Technology (Finland)

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Color Image ProcessingColor Image Processing

Fundamentals Color models Pseudocolor image processing Full color image processing Color transformations Smoothing and Sharpening Color segmentation Noise in color images Color image compression Multispectral image processing

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Fundamentals

Colors in the visible range of wavelengths (upper left), mixtures of light (additive primaries) (upper right) and color bars used in analysis.

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Color models

Relative color gamuts of a dipslay and a printer in XYZ chromaticity coordinate system (right).

Left - XYZ color space.

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Color models

http://cvision.ucsd.edu/index.htm

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Color models

RGB system, HSI (or HSV) system (right) (I-intensity, V value)

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Color models

Three match curves. RGB system (CIE 1931)(left), XYZ system (CIE 1931)(right)

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Color models

RGB space. The right image is a rotated left image (for correspondence: BL is black, W is white).

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Hue, saturation, intensity system

Y aR cG dBr g b

r g bW P

W Sr g b

U

V|||

W|||

arccos[( / ) ( / ) ( / ) ]

min( , , )

/

2

6 1 3 1 3 1 3

1 3

2 2 2 1 2

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Color models

Chromaticity

r R R G B

g G R G B

b B R G B

UV|W|

/ ( )

/ ( )

/ ( )

g

r0r g b 1b r b 1

w( / , / )1 31 3

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Color models

Multitriangle representation (left) Luminance, chromaticity (right)

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Color models

Karhunen-Loev system

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Pseudocoloring

Myocardial perfusion study. Left is a heart attack (blue region increased), right is normal.

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Pseudocoloring. X-rays.

a

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Pseudocoloring

Right – three images: elevation relief (upper left), the color coded magnetic field (higher values are yellowish) (upper right), the composition of first two. Left – underpainting revealed through color dipslay (Prof. L. MacDonald, Derby University,GB).

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Thematic classification of six-band satellite imagery using a minimum distance classifier

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Painting Restoration. A Queen house , London. The part of painting was copied from another painting (upper right) and

used for restoration of the lost painting part.

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Color segmentation

Image segmentation based on color feature: burnt forest area, forest fire, dead forest (brown).

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Color image compression.

Original color image (upper left), compressed image (upper right), error histogram in compression (the error is a delta E – the smallest color noticible difference) and error image (large error values are white).

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Using a ratio image to enhance road detail (two upper is a multispectral image components)

The third image (lower) is the dividend of the first two

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Color analysis. Color similarity

Brick Ceramic tiles Wooden pieces Car parts

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Color analysis. The Munsell Book of Color contains a set of color patches

http://www.it.lut.fi/research/color/demonstration/demonstration.html

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Color analysis. Metameric spectra. Color is the same at one illumination (left patches) and different at another

illumination (right patches).

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Statistical Analysis of Natural ImagesUpper curve is mean, lower curve is standard deviation

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http://www.techexpo.com/WWW/opto-knowledge/ for previous picture site.

http://stargate.jpl.nasa.gov/lctf/ for this picture site.

Documents

1 Vladimir Botchko [email protected] Lecture 5. Color Image Processing Lappeenranta University of Technology (Finland)