01.12.2014
Median Filter (Ortanca Süzgeç)
IMAGE PROCESSING
Lecture-5
• Rank order filter
• Non-linear
• Useful in impulsive and salt-pepper noise
• Can distort image boundaries
Median Filtering
Color
25, 28, 29, 34, 38, 41, 45, 46, 56
New Pixel Values
• Note: imnoise adds noise in MATLAB
1 Aralık 2014
Median Filter
2
Color
• Imporant descriptor for scenes & objects .
• Two Categories:
•Full color
•Pseudo color
Acquired using color sensor
Noisy Image
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3x3 Mean
Filter
• Note: medfilt2 can be used in MATLAB
3x3 Median
Filter
Artificially colored
3
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4
Color-Electromagnetic Spectrum
RGB Color Model
• Optik Prizma (Isaac Newton-1666)
Every pixel has an R,G,B value.
B
(Usually represented in 8 bits)
1 blue
white
cyan
0
• If there is no color, there is only light intensity
1
magenta
green
1
black
R
red
yellow
G
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1
01.12.2014
Color Models- RGB
Color Models
• RGB
G
Y
R
W
Main Colors (CMY)
Main Colors (RGB)
C
M
B
(Y)
(G)
(R)
(Y)
(R)
(W)
(M)
(C)
(M)
(B)
(B)
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(G)
(B)
(C)
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Color Models- CMY
RGB Model
• RGB 2 CMY:
Kids image
“Kids”
 C  1  R 
 M   1  G 
    
 Y  1  B 
Red color components of the image
,
 R  1  C 
G   1   M 
    
 B  1  Y 
• CMYK used for pure black.
Green color components of the image
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Blue color components of the image
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HSI Model



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HSI Model
H : hue (renklilik)
S : saturation (doygunluk)
I : intensity (ışıklılık)
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“Kids” image
Hue components of the image
Saturation components of the image
Intensity components of the image
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2
01.12.2014
Color Models
Color Model Comparison
• RGB (Red, Green, Blue):
•Monitors, Cameras.
• CMY (Cyan, Magenda, Yellow), CMYK (Cyan, Magenda, Yellow, blacK)
•Printer.
• HSI ((Hue,, Saturation,, Intensity)
y)
•Classificatiob.
• YIQ
•NTSC.
• YCbCr
•ColorTV.
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Color Models– MATLAB
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RGB -> Grey
MATLAB Color transformation
• RGB → ...
• YCbCr
rgb2ycbcr
•YIQ
rgb2ntsc
• HSI
rgb2hsv
• ... → RGB
• YCbCr
ycbcr2rgb
•YIQ
ntsc2rgb
• HSI
hsv2rgb
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Compression of Color Images
JPEG:
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Compression of Color Images
Y  0.3R  0.6G  0.1B
Cr  0.5  (R  Y ) / 2
Cb  0.5  (B  Y ) /1.6
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3
01.12.2014
JPEG Compression of Color Images
Non-Interleaved :
Y1, Y2, Y3,…,Y16
Cr1,Cr2,Cr3,Cr4
Cb1,Cb2,Cb3,Cb4
Interleaved :
Y1, Y2, Y3,Y4,Cr1,Cb1,Y5,Y6,Y7,Y8,Cr2,Cb2,…
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