Shadow removal

Team FCorina Blajovici

Zoltán BónusPéter József Kiss

László Varga

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1. Our main goalRemove shadows from pictures without

user interactionCan be separeted to two different tasks:

SSIP 2011 - Shadow removal

1. Find the shadow (shadow mask)

2. Remove the shadow

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2. Shadow detection1) 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)

SSIP 2011 - Shadow removal

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3. Shadow removalWe implemented 3 different algorythms for

this task:1. Additive correction of shadow pixel colors2. Light-model based color correction

3. Combination of the first two in Ycbcr colorspace

SSIP 2011 - Shadow removal

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4. Results (1/6)

SSIP 2011 - Shadow removal

Additive method Light-model based method Combinative method

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4. Results (2/6)

SSIP 2011 - Shadow removal

Additive method Light-model based method Combinative method

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4. Results (3/6)

SSIP 2011 - Shadow removal

Additive method Light-model based method Combinative method

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4. Results (4/6)

SSIP 2011 - Shadow removal

Additive method Light-model based method Combinative method

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4. Results (5/6)

SSIP 2011 - Shadow removal

Additive method Light-model based method Combinative method

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4. Results (6/6)

SSIP 2011 - Shadow removal

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”.

SSIP 2011 - Shadow removal

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Final ConclusionsAnyway, 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