[vals,r,c] = qtgetblk(I,S,dim)
returns blocks of size dim-by-dim from image
I with quadtree decomposition S. The function returns
the block values in vals and the row and column coordinates of the upper
left corner of the blocks in r and c.

[vals,idx] = qtgetblk(I,S,dim)
returns the block values in vals and the linear indices of the upper left
corners of the blocks in idx.

Perform a quadtree decomposition of the image, specifying a threshold of 5. qtdecomp splits a block if the maximum value of the block elements minus the minimum value of the block elements is greater than the threshold.

Data Types: single | double | int16 | uint8 | uint16 | logical

S — Quadtree structure sparse matrix

Quadtree structure, specified as a sparse matrix. If
S(m,n) is nonzero, then the
coordinate (m,n) is the upper left corner of a block in
the decomposition, and the size of the block is given by
S(m,n). You can get a quadtree
structure by using the qtdecomp function.

Block values, returned as a
dim-by-dim-by-k array, where
k is the number of dim-by-dim blocks
in the quadtree decomposition. If the quadtree decomposition contains no blocks of the
specified size, then vals is returned as an empty matrix.

The ordering of the blocks in vals matches the columnwise order of
the blocks in I. For example, if vals is 4-by-4-by-2,
then vals(:,:,1) contains the values from the first 4-by-4 block in
I, and vals(:,:,2) contains the values from the second
4-by-4 block.

r — Row coordinates of upper left corners of blocks k-element column vector | []

Row coordinates of the upper left corners of blocks, returned as a
k-element column vector of positive integers, where k is
the number of dim-by-dim blocks in the quadtree
decomposition. If the quadtree decomposition contains no blocks of the specified size, then
r is returned as an empty matrix.

c — Column coordinates of upper left corners of blocks k-element column vector | []

Column coordinates of the upper left corners of blocks, returned as a
k-element column vector of positive integers, where k
is the number of dim-by-dim blocks in the quadtree
decomposition. If the quadtree decomposition contains no blocks of the specified size, then
c is returned as an empty matrix.

idx — Linear indices of upper left corners of blocks k-element column vector | []

Linear indices of upper left corners of blocks, returned as a
k-element column vector of positive integers, where k is
the number of dim-by-dim blocks in the quadtree
decomposition. If the quadtree decomposition contains no blocks of the specified size, then
idx is returned as an empty matrix.

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