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Chromatic Framework for Vision in Bad Weather. Srinivasa G. Narasimhan and Shree K. Nayar Computer Science Department Columbia University IEEE CVPR Conference June 2000, Hilton Head Island, USA Sponsors: ONR MURI , NSF. Dense Fog. Noon Haze. B. B. R. R. G. G.

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chromatic framework for vision in bad weather

Chromatic Framework for Vision in Bad Weather

Srinivasa G. Narasimhan and Shree K. Nayar

Computer Science Department

Columbia University

IEEE CVPR Conference

June 2000, Hilton Head Island, USA

Sponsors:

ONR MURI , NSF

the colors of bad weather

Dense Fog

Noon Haze

B

B

R

R

G

G

The Colors of Bad Weather

Clear Day

B

R

G

slide3

General Color Framework for

Analysis of Bad Weather Images

OUR GOAL :

Prior Work

  • Overviews : Middleton 1952 , McCartney 1976
  • Haze : Hulburt 1946 , Hidy 1972
  • Fog : Koshmeider 1924 , George 1951 , Myers 1968
  • Vision :
  • Cozman & Krotkov 1997 - Depth Cues from Iso-Intensities
  • Nayar & Narasimhan 1999 - Complete Structure ; Restricted weather conditions
slide4

( Allard, 1876 )

( Koschmieder, 1924 )

Diffuse

Skylight

Sunlight

Diffuse

Ground Light

E

E

Direct Transmission

Airlight

Direct Transmission and Airlight Models

Object

Observer

d

dichro matic atmospheric scattering model

Direct Transmission

(True Color )

Airlight

(Fog / Haze Color)

Model :

Dichromatic Atmospheric Scattering Model

( Nayar & Narasimhan, 1999 )

B

E

R

G

dichromatic planes

Verification :

Scene (800 x 600 pixels)

Avg. Error (degrees)

0.25 º

Foggy

Hazy

0.31 º

Dichromatic Planes

Direct Transmission

Color

Dichromatic

Plane

Airlight

Color

direction of airlight fog or haze color

Plane 2 (Scene Point O)

Airlight Color from Planes :

Direction of Airlight ( Fog or Haze ) Color

Plane 1 (Scene Point X)

Weather Condition 1

Weather Condition 2

slide8

,

,

Sky Brightnesses :

( Unknown )

Direct Transmission Ratio

Scaled Depth

Ratio of Direct Transmissions :

Depth of a Scene Point :

Sky Brightness Ratio

Depth from Unknown Weather Conditions

Scattering Coefficients :

( Unknown )

direct transmission ratio

Direct Transmission Ratio :

Direct Transmission Ratio

Direct Transmission

Color

Dichromatic

Plane

Airlight

Color

sky brightnesses

Relative Airlight

Depth of a Scene Point

Relation Between Sky Brightnesses

Sky Brightnesses

Direct Transmission

Color

Dichromatic

Plane

Airlight

Color

slide11

Recovered Structure

Fog 2 + Noise

Fog 1 + Noise

Results with a Synthetic Scene

Color Patches

Rotated Structure

simulation results

1.5

2.5

2.0

0.5

1.0

3.0

Noise

0

Estimated

200.02

200.65

201.4

200.23

200.96

202.1

200

401.1

403.6

400.02

400.4

400.60

405.8

Estimated

400

Depth Error (%)

0.0

0.63

0.36

0.79

0.53

0.93

0.54

Actual Values =

Simulation Results

0.5

1.5

2.5

1.0

2.0

3.0

Noise

0

Estimated

100.02

100.65

103.23

100.55

101.26

104.84

100

258.2

260.13

255.02

255.4

256.61

263.45

Estimated

255

Depth Error (%)

0.0

0.82

0.42

0.89

0.58

0.96

0.76

Actual Values =

slide13

Computed Depth Map

Structure from Two Weather Conditions

Scene under two different Hazy Conditions

slide14

Computed Depth Map

Structure from Two Weather Conditions

Scene under two different Foggy Conditions

slide15

Minimum Time to Collision

Min

First Collision with Color Boundary

True Color Recovery - Color Cube Boundary Algorithm

1

2

3

B

O

G

R

slide16

Computed True Color

True Color Recovery

Scene under two different Foggy Conditions

( Brightened )

slide17

Color Framework for Vision in Bad Weather

Summary

  • Airlight Color from Dichromatic Planes
  • Scene Depth from Dichromatic Constraints
  • True Color fromColor Boundary Constraint