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qtgetblk - Block values in quadtree decomposition

Syntax

[vals, r, c] = qtgetblk(I, S, dim) [vals, idx] = qtgetblk(I, S, dim)

Description

[vals, r, c] = qtgetblk(I, S, dim) returns in vals an array containing the dim-by-dim blocks in the quadtree decomposition of I. S is the sparse matrix returned by qtdecomp; it contains the quadtree structure. vals is a dim-by-dim-by-k array, where k is the number of dim-by-dim blocks in the quadtree decomposition; if there are no blocks of the specified size, all outputs are returned as empty matrices. r and c are vectors containing the row and column coordinates of the upper left corners of the blocks.

[vals, idx] = qtgetblk(I, S, dim) returns in idx a vector containing the linear indices of the upper left corners of the blocks.

Class Support

I can be of class logical, uint8, uint16, int16, single, or double. S is of class sparse.

Remarks

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, 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.

Examples

I = [1    1    1    1    2    3    6    6
     1    1    2    1    4    5    6    8
     1    1    1    1   10   15    7    7
     1    1    1    1   20   25    7    7
    20   22   20   22    1    2    3    4
    20   22   22   20    5    6    7    8
    20   22   20   20    9   10   11   12
    22   22   20   20   13   14   15   16];
 
 S = qtdecomp(I,5);

[vals,r,c] = qtgetblk(I,S,4)