Image Processing Toolbox User's Guide |

Get block values in quadtree decomposition

**Syntax**

**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.

**Example**

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)

**See Also**

qtdecomp | qtsetblk |

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