Single Image Haze Removal Using Dark
Channel Prior
Professor : 王聖智 教授
Student : 戴玉書
CVPR 2009 . Best Paper Award Kaiming He, Dept. of Inf. Eng., Chinese Univ. of Hong Kong, Hong Kong, ChinaJian Sun Xiaoou Tang, Dept. of Inf. Eng., Chinese Univ. of Hong Kong, Hong Kong, China
OutlineOutline
Background Background What is the Dark Channel Prior?What is the Dark Channel Prior? How to estimate How to estimate atmospheric light?? Estimating the transmission t(x) & Soft MaEstimating the transmission t(x) & Soft Ma
ttingtting Recovering the Scene RadianceRecovering the Scene Radiance ResultResult
BackgroundBackground
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Observed intensity
Scene radiance
The global atmospheric light
The medium transmission,
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OutlineOutline
Background Background What is the Dark Channel Prior?What is the Dark Channel Prior? How to estimate How to estimate atmospheric light? light? Estimating the transmission t(x) & Soft MaEstimating the transmission t(x) & Soft Ma
ttingtting Recovering the Scene RadianceRecovering the Scene Radiance ResultResult
Dark Channel PriorDark Channel Prior Observation on haze-free outdoor images: Observation on haze-free outdoor images: In most of the non-sky patches, at least one colIn most of the non-sky patches, at least one col
or channel has very low intensity at some pixelor channel has very low intensity at some pixelss
{ , , } ( )( ) min ( min ( ( )))dark c
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Mainly due to three factorsMainly due to three factors
ShadowsShadows Colorful of objects or surfacesColorful of objects or surfaces Dark objectsDark objects
haze-free image The dark channel of haze-free image
Statistics of the dark Statistics of the dark channelschannels
Except for the sky region, the intensity of is low and Except for the sky region, the intensity of is low and tends to be zerotends to be zero
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Visually, the intensity of the dark channel is rough
approximation of the thickness of the haze
haze image The dark channel of haze image
OutlineOutline
Background Background What is the Dark Channel Prior?What is the Dark Channel Prior? To estimate of To estimate of atmospheric light light Estimating the transmission t(x) & Soft MaEstimating the transmission t(x) & Soft Ma
ttingtting Recovering the Scene RadianceRecovering the Scene Radiance ResultResult
To estimate of To estimate of atmospheric light
Pick the top 0.1% brightest pixels in the dark Pick the top 0.1% brightest pixels in the dark channelchannel
OutlineOutline
Background Background What is the Dark Channel Prior?What is the Dark Channel Prior? How to estimate How to estimate atmospheric light? light? Estimating the transmission t(x) & Soft MaEstimating the transmission t(x) & Soft Ma
ttingtting Recovering the Scene RadianceRecovering the Scene Radiance ResultResult
Estimating the transmission Estimating the transmission
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Soft MattingSoft Matting
Image matting equation:Image matting equation:
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Minimize the following cost function:
A. Levin, D. Lischinski, and Y. Weiss. A closed form solutionto natural image matting. CVPR, 1:61–68, 2006. 4, 5, 7
OutlineOutline
Background Background What is the Dark Channel Prior?What is the Dark Channel Prior? How to estimate How to estimate atmospheric light? light? Estimating the transmission t(x) & Soft MaEstimating the transmission t(x) & Soft Ma
ttingtting Recovering the Scene RadianceRecovering the Scene Radiance ResultResult
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OutlineOutline
Background Background What is the Dark Channel Prior?What is the Dark Channel Prior? How to estimate How to estimate atmospheric light? light? Estimating the transmission t(x) & Soft MaEstimating the transmission t(x) & Soft Ma
ttingtting Recovering the Scene RadianceRecovering the Scene Radiance ResultResult
ResultResult
The patch size is set to 15x15 The patch size is set to 15x15 Soft matting: Preconditioned Conjugate GSoft matting: Preconditioned Conjugate G
radient (PCG) algorithmradient (PCG) algorithm Local min operator using Marcel van HerkLocal min operator using Marcel van Herk
’s ’s fast algorithmfast algorithm
► Tan's resultTan's result
► Fattal's resultFattal's result
► Dark channelDark channel
► Tan's resultTan's result
► Fattal's resultFattal's result
► Dark channelDark channel
► Kopf et al's resultKopf et al's result
► Dark channelDark channel
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