I'm trying to develop a class in Java able of performing the Laplacian
pyramid of a given image in order to use it to later construction of mosaic
applications, but i'm finding some troubles in the initial step: the
Gaussian pyramid.
This is the explanation of the Gaussian pyramid construction algorithm of
Burt and Adelson (The Laplacian Pyramid as a compact Image Code. IEEE
Trans. April 1983) . We suppose the image is represented initially by the
array G0 which contains C columns and R rows of pixels. Each pixel
represents the light intensity at the corresponding image point by an
integer I between = and K -1. This image becomes the bottom or zero level
of the Gaussian pyramid. Pyramid level 1 contains image G1, which is a
reduced or low-pass filtered version of G0. Each value within level 1 is
computed as a weighted average of values in level 0 within a 5-by5 window.
Each value within level 2, representing G2, is then obtained from values
within level 1 by applying the same pattern of weights.
Thus, the level to level averaging process is performed by the function
REDUCE,
Gk = REDUCE(Gk-1)
which means, for levels 0 < f < N and nodes i,j,
0 <= i < Cf,
0 <= j < Rf
2 2
Gf(i,j) = Sum Sum w(m,n) Gf-1(2i+m, 2j+n)
m=-2 n=-2
Where w(m,n) is the generating kernel used to convolve the image.
This way, the value of each node in the zero level is just the gray level
of a corresponding image pixel. The value of each node in a high level is
the weighted average of node values in the next lower level. The result we
obtain is a of the density of the nodes by half in one dimension or by
fourth in ywo dimensions from level to level.
I'm trying to fulfill this method by means of a combination of ConvolveOp
(for the convolution with w kernel) and RescaleOp (for the multiplication
and offset of Gf-1) Java2D classes, but I don't get the expected result as long as
the density of the nodes is the same so the size of the image doesn't change.
Maybe somebody knows about this problem and can help me.
Thanks in advance.
Daniel
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