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tilted integral sum

asked 2013-02-19 12:21:22 -0500

Bibliarij gravatar image

updated 2013-02-19 12:23:32 -0500

Hello all! Is getting of tilted integral sum is necessarily for implementing Viola-Jones method? It seems to me that I saw some realizations which don't use tilted integral sum. This kind of integral image is some strange for me, I can't understand it...

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answered 2013-02-19 16:40:31 -0500

SR gravatar image

No, the tilted integral image is not needed for the Viola Jones algorithm. In fact, the original Viola Jones Paper only uses upright (=untilted) Haar-like features.

In An Extended Set of Haar-Like Features for Rapid Object Detection, Rainer Lienhart , Jochen Maydt, ICIP 2002 the authors showed that extending the original feature set with those tilted Haar-like features improves performance, i.e. the false positive rate was reduced.

AFAIK the Haar-cascade detector in OpenCV uses both normal and tilted Haar-like features by default. I suppose other object classes benefit more from tilted features than faces.

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I have one additional question. I use cascade file haarcascade_frontalface_alt.xml. Does the word "alt" mean that this cacsade doesn't use titled features?

Bibliarij gravatar imageBibliarij ( 2013-02-20 02:53:06 -0500 )edit

I have no clue.

SR gravatar imageSR ( 2013-02-20 04:56:05 -0500 )edit

ok, thanks

Bibliarij gravatar imageBibliarij ( 2013-02-20 05:11:50 -0500 )edit

answered 2013-02-19 13:47:28 -0500

berak gravatar image

updated 2013-02-19 13:50:53 -0500

yes, it's essential. please read the paper:

the viola-jones method is all about comparing rectangles, is the left one brighter than the right ? comparing rectangles

with those integral images, the check is just a handful of array lookups and adds, without, you'd have to loop through the image region every time, to get it's intensity

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This is not the answer for the question. It is just about integral images in general.

SR gravatar imageSR ( 2013-02-19 16:34:04 -0500 )edit

well oh, i assumed the guy's problem was understanding integral images, thus a wish to sidestep them. my intent here was more to highlight the importance of the 'integral' thing for this.

berak gravatar imageberak ( 2013-02-19 16:56:46 -0500 )edit

Yeah, maybe I say not very clear... I can't understand only titled integral image. Anyway thanks to the answer!

Bibliarij gravatar imageBibliarij ( 2013-02-20 00:29:43 -0500 )edit

Hi Bibliarij, i'm facing same problem like you, I can't understand tilted integral sum. Did you understand it now?

livina gravatar imagelivina ( 2013-07-24 21:50:23 -0500 )edit
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Asked: 2013-02-19 12:21:22 -0500

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Last updated: Feb 19 '13