image perception and color space
DESCRIPTION
Image Perception and Color Space. Human Eye. Simultaneous Contrast. luminance vs. brightness Contrast Weber’s Law:. Mach Band. Lateral inhibition. Herman Grid. Blind Spot Test. Blind Spot Test. Blind Spot Test. Blind Spot Test. Color Representation. Visual Spectrum. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/1.jpg)
Image Perception and Color Space
![Page 2: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/2.jpg)
Human Eye
![Page 3: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/3.jpg)
Simultaneous Contrast
• luminance vs. brightness
• Contrast– Weber’s Law: constant
f
f
![Page 4: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/4.jpg)
Mach Band
• Lateral inhibition
0 50 100 150 200 250-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
![Page 5: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/5.jpg)
Herman Grid
![Page 6: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/6.jpg)
Blind Spot Test
![Page 7: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/7.jpg)
Blind Spot Test
![Page 8: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/8.jpg)
Blind Spot Test
![Page 9: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/9.jpg)
Blind Spot Test
![Page 10: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/10.jpg)
Color Representation
![Page 11: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/11.jpg)
Visual Spectrum
Red 700 nm
Green 546.1 nm
Blue 435.8 nm
![Page 12: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/12.jpg)
Perceptual Representation (HSV)
![Page 13: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/13.jpg)
CIE Color Chart
CIE XYZ
![Page 14: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/14.jpg)
![Page 15: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/15.jpg)
![Page 16: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/16.jpg)
YUV Color Space
• Y is luminance of a colorY = 0.299*R’ + 0.587*G’ + 0.114*B’
• U and V are color differencesU = 0.492*(B’-Y)V = 0.877*(R’-Y)
• This simplifies recovery of R’,G’,B’– R’ = Y - 1.140V– G’ = Y - 0.394U - 0.581V– B’ = Y + 2.032U
![Page 17: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/17.jpg)
YIQ Color Space
• Rotate UV vectors by 30o
V
U
Q
I
)33cos(
)33sin(
)33sin(
)33cos(
0
1
1
0
U
V
Q
I
![Page 18: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/18.jpg)
YIQ Color Space
I = 0.736*(R’-Y) - 0.268(B’-Y)
Q = 0.478*(R’-Y) + 0.413*(B’-Y)
Recovery of R,G,B
R’ = Y - 0.956*I + 0.620*Q
G’ = Y - 0.272*I - 0.647*Q
B’ = Y - 1.108*I - 1.705*Q
![Page 19: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/19.jpg)
YCbCr
• Scaled and offset version of YUV
• Range of signalsY: 16~235
Cb,Cr: 16~240
• Suitable for digital images/video
![Page 20: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/20.jpg)
YCbCr Color SpaceBegin by calculating R-Y and B-Y vectors
B’-Y = -0.299*R’ - 0.587*G’ + 0.886*B’
R’-Y = 0.701*R’ - 0.587*G - 0.114*B’
The difference signals have ranges
B’-Y (-.866 to .866)
R’-Y (-.701 to .701)
Scale to range (-.5 to .5) to give same range as Y (0 to 1)
Cb = -.169*R’ - .331*G’ + .500*B’ = .564(B’-Y)
Cr = .500*R’ - .419*G’ - .081*B’ = .713(R’-Y)
![Page 21: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/21.jpg)
YCbCr Color SpaceFor computer representation, Scale and offset these values to keep in
range 16 to 240 (Cb and Cr) or 16 to 235 (Y)
Cb = 224*Cb + 128 = 126.336(B’-Y) + 128
Cr = 224*Cr + 128 = 159.712(B’-Y) + 128
Y = 219*Y + 16
Finally,
128
128
16
071.0368.0439.0
439.0291.0148.0
098.0504.0257.0
B
G
R
C
C
Y
r
b
![Page 22: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/22.jpg)
CMYK Color Space
• Subtractive color space• Most common use is for printers
– K (black) is added for efficiency and consistency
– White cannot be generated w/o white paper
Example: Cyan represents green and blue, by adding cyan we subtract the color red from sum.
![Page 23: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/23.jpg)
Perception? Illusion?
![Page 24: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/24.jpg)
Masking Effect
![Page 25: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/25.jpg)
Masking Effect
![Page 26: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/26.jpg)
Necker Cube
![Page 27: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/27.jpg)
![Page 28: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/28.jpg)
![Page 29: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/29.jpg)
Which is longer?
![Page 30: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/30.jpg)
Poggendorff Illusion
![Page 31: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/31.jpg)
Ponzo Illusion
![Page 32: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/32.jpg)
Adaptation
![Page 33: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/33.jpg)
Adaptation
![Page 34: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/34.jpg)
Adaptation
![Page 35: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/35.jpg)
Adaptation
![Page 36: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/36.jpg)
Are they straight lines?
![Page 37: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/37.jpg)
Which is longer?
![Page 38: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/38.jpg)
Stereo Vision
![Page 39: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/39.jpg)
Autostereogram
![Page 40: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/40.jpg)
What do you see?
![Page 41: Image Perception and Color Space](https://reader036.vdocuments.site/reader036/viewer/2022062421/56812a44550346895d8d7817/html5/thumbnails/41.jpg)
What do you see?