A detected window contains a face if and only if a sufficient number of other adjacent detected
windows of the same size confirm it. To require windows of exactly the same size is not stringent
because the test window sizes are quantified (see Algorithm 7 line 2). In this implementation,
the window size multiplier is 1.5. Two e×e detected windows are said to be adjacent if and only
if between the upper left corners of these two windows there is a path formed by the upper left
corners of some detected windows of the same size. This condition is easily checked with the
connected component algorithm5
[8]. The number of test windows detecting a face is presumed
to grow linearly with its size. This suggests the quotient of the cardinality of a connected
component of adjacent windows by their common size e as an adequate confidence measure