Transcript Shadow removal - u

Shadow removal
Team F
Corina Blajovici
Zoltán Bónus
Péter József Kiss
László Varga
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1. Our main goal
 Remove
shadows from pictures without
user interaction
 Can be separeted to two different tasks:
1. Find the shadow (shadow mask)
2. Remove the shadow
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2. Shadow detection
1)
Histrogram dissension
2)
Iterate through the Y channel of the picture in Ycbcr
colorspace
3)
Start with NxN size window, and compare intensities
with the average of the whole picture and the window
4)
Pixels with lower intensity will be marked as shadows
5)
Repeat from the third step with smaller window size, but
only modify the unmarked pixels (until window size
reaches 3x3)
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3. Shadow removal
 We
implemented 3 different algorythms for
this task:
1.
2.
3.
Additive correction of shadow pixel colors
Light-model based color correction
Combination of the first two in Ycbcr
colorspace
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4. Results (1/6)
Additive method
Light-model based method
Combinative method
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4. Results (2/6)
Additive method
Light-model based method
Combinative method
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4. Results (3/6)
Additive method
Light-model based method
Combinative method
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4. Results (4/6)
Additive method
Light-model based method
Combinative method
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4. Results (5/6)
Additive method
Light-model based method
Combinative method
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4. Results (6/6)
Additive method
Light-model based method
Combinative method
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5. Conclusions

Shadow Removal is a hard task!

What we reached, and what still can be improved:

A system that can remove shadow from homogenious
texrute.

A segmentation approach to detect crisp shadows on an
image.


Probably a ‘fuzzy’ shadow membership on the pixels would give
a better description.
Thre methods for the removal of shadows:


Some actually works fine, but has no mathematical backgorund.
Some has a nice mathematical description, but unfortunately the
„World is not willing to follow the model to the letter”.
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Final Conclusions
 Anyway,
the system is not perfect, but it
can work on lots of images.
 Using it and being lucky can just work
fine! 
SSIP 2011 - Shadow removal