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Analysis and Comparison of Quality Metrics with Reference
Based on Uniform Color Spaces
Gabriel Dauphin,
PatrickPatrick Viaris de Lesegno
L2TI, Institut Galilée,
Université Paris 13
EUVIP 2010
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Outline• Three quality metrics are studied :
PSNR, VDP, SSIM
1.Are they consistent with Weber’s law?
2.Is Weber’s law consistent with HVS?
Analytic Experience
I V
II III
IV
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• .
• VDP
• SSIM
Consistent with Weber’s Law?
Mean
MeanMaxM L
LLC
I
DK
Dkl
RK
Rkl
kl B
B
B
BC
M
jDj
Rj
RDj
Dj
Rj
Dj
Rj
M 12222
221
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Color Spaces and Gamma Correction Say NO• CIE L*a*b* 1976 :
• Gamma Correction
L
L
L
LLLE
L
L
f
3
11160
31
Re
31
*1
*2
II
31
31
Re
1
116
322
LL
L
LCE fW
MaxMax g
gLL
1
1 1,0
Lg
gL
L
LCgg
L
L
Max
ThMaxWTh
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Psychovisual Tests Say NO
31
31
BW
BW
LS
LC
III
29
65
147
31
1025.229
65
65
147
[Y.-K. Lai and C.-C.J. Kuo 2000]
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New Photometric Invariance Law
1'
',, mnmnmnmnmnmn LLLQLLLQ
33.0
IV
Q consistent with HVS wrt its sensitivity to backgound Lum.Q consistent with Weber’s law0
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Numerical SimulationsV
PSNR:=0.42
VDP:=-0.04
SSIM:]42.0,0[
0iC
0
SSIM
PSNR => YesVDP, SSIM => No 0iC
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Conclusion
• Weber’s law => VDP,SSIM[Ci=0] HVS• Photometric invariance law and simulation tool • Yet Weber’s contrast may improve rendering => this should be application driven• Many aspects of image processing are already
consistent with HVS => good news for quality assessment