Thecrucialattributeoftheimagepotentialenergymodelisthatimagepotentialenergyrelatedtotheobjectisalmostinvariablenomatterhowfartheobjectisfromthecamera.Let denotetheaverage ofonepersonand denotetheestimationofthecrowddensity.Wecanestimatethecrowddensityasfollows:
=
.
(2)
(a)Original
frame(b)
Foreground
(c) (
)
Fig.4.
(d) ( )
Foregroundhistogram.
Thecalculatedhistogramsindicatestheforegrounddis-tributiononthehorizontalandverticaldirection.Fig.4isanexampleofforegroundhistograms.Theframesizeis320*240.
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