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Can Viola-Jones face detection in opencv works for 25 feet? If the camera is good and capable of good quality picture is it possible for Viola-Jones to detect the face?

2vision2
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  • The best approach would be to try it with your camera. "for 25 feet" is pretty much meaningless. – Bull Jun 24 '13 at 06:40
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    Rough numbers you could have gotten yourself by pointing a camera at yourself: My camera's vertical FOV is 4 faces high @ 2.5 feet away. The highest resolution you're likely to use is 1920x1080. Many detectors internally use a 24x24 window. 24px fits 45 times in 1080px. 45/4 is ~ 11. And 2.5 feet * 11 = 27.5 feet. Assuming you actually have the computational horsepower to run V-J for objects as small as 24x24 within 1080p frames (_big if_), you might just do it, although personally I've never tried detecting faces smaller than 50x50 within 640x480 frames due to noise and slow speed. – Iwillnotexist Idonotexist Dec 24 '13 at 21:09

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Yes, of course, particularly if a zoom lens is used.

Bull
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  • Wasn't sure if this was sarcastic or not. But it's certainly true depending on the zoom! – bjou Jun 25 '13 at 15:57
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In the XML file of your classifier, there is section which specifies minimum size of window (2 lines behind featuretype tag). So as long as your face ROI is equal or greater than that size (in terms of pixel), yes it will detect. But speed might decrease drastically if the image size is too big than minimum size window (since it's kind of exponential thing)

BilguunCH
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