analysis and comparison of quality metrics with reference based on uniform color spaces
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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
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
• .
• 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
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
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]
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
Numerical SimulationsV
PSNR:=0.42
VDP:=-0.04
SSIM:]42.0,0[
0iC
0
SSIM
PSNR => YesVDP, SSIM => No 0iC
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
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