Retinex by Two Bilateral Filters Michael Elad The CS Department The Technion – Israel Institute of technology Haifa 32000, Israel Scale-Space 2005 The 5 th international conference on scale-space and PDE in computer vision Hofgeismar, Germany April 7-9 th , 2005
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Retinex by Two Bilateral Filters Michael Elad The CS Department The Technion – Israel Institute of technology Haifa 32000, Israel Scale-Space 2005 The.
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Retinex by Two Bilateral Filters
Michael EladThe CS Department
The Technion – Israel Institute of technologyHaifa 32000, Israel
Scale-Space 2005The 5th international conference on scale-space
and PDE in computer visionHofgeismar, Germany
April 7-9th , 2005
Retinex by TwoBilateral FiltersBy: Michael Elad
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Retinex?
Retinex by TwoBilateral FiltersBy: Michael Elad
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Agenda
1. What is Retinex? The Basics
2. Retinex from a Variational Point of View
3. Bilateral Filter? Evolution of Denoising Methods
4. Bilateral Filter For Retinex
5. Examples and What Next?
Retinex by TwoBilateral FiltersBy: Michael Elad
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Part 1
What is Retinex? The Basics
Retinex by TwoBilateral FiltersBy: Michael Elad
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What is Retinex?
The sensed image is S=LR, where: S – Scene intensity,
L – illumination, R – reflectance.
We can measure S, but not L or R.
Getting R from S is an ill-posed inverse problem.
The human visual system (HVS) sees R. How?
Retinex is a similar image enhancement algorithm.
Retinex by TwoBilateral FiltersBy: Michael Elad
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A Typical Retinex System
RLS Rlogr
,Llog
,Slogswhere
rs
STake log
s Extract
+_
r Take exp
R
Retinex by TwoBilateral FiltersBy: Michael Elad
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Example: Gamma Correction
Gamma correction is a simple Look-Up- Table operation of the form (γ2.5)
γ/1
255S
255S
SGamma
Correction
S
255logs1
1ˆ
In
Out
Retinex by TwoBilateral FiltersBy: Michael Elad
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A new Algorithm
Many Retinex Algorithms …
Various Retinex algorithms out there: Random walk smoothing [Land and MacCan 1971]