Integral image, returned as a numeric array. The function zero-pads the top, left and along
the first plane, resulting in size(J) = size(I) + 1. side
of the integral image. The class of the output is double.
The resulting size of the output integral image equals: size(J) =
size(I) + 1. Such sizing facilitates easy computation of pixel
sums along all image boundaries. The integral image, J,
is essentially a padded version of the value
cumsum(cumsum(cumsum(I),2),3).
In an integral image, every pixel is the
summation of the pixels above and to the left of it. Using an integral image, you
can rapidly calculate summations over image subregions. Use of integral images was
popularized by the Viola-Jones algorithm. Integral images facilitate summation of
pixels and can be performed in constant time, regardless of the neighborhood
size.