# Documentation

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# labelmatrix

Create label matrix from `bwconncomp` structure

## Syntax

`L = labelmatrix(CC)`

## Description

`L = labelmatrix(CC)` creates a label matrix from the connected components structure `CC` returned by `bwconncomp`. The size of `L` is `CC.ImageSize`. The elements of `L` are integer values greater than or equal to 0. The pixels labeled `0` are the background. The pixels labeled `1` make up one object; the pixels labeled `2` make up a second object; and so on. The class of `L` depends on `CC.NumObjects`, as shown in the following table.

ClassRange
`'uint8'`

`CC.NumObjects` $\le$ 255

`'uint16'`

256 $\le$ `CC.NumObjects` $\le$ 65535

`'uint32'`

65536 $\le$ `CC.NumObjects` $\le {2}^{32}-1$

`'double'`

`CC.NumObjects` $\ge {2}^{32}$

`labelmatrix` is more memory efficient than `bwlabel` and `bwlabeln` because it returns its label matrix in the smallest numeric class necessary for the number of objects.

## Class Support

`CC` is a structure returned by `bwconncomp`. The label matrix `L` is `uint8`, `uint16`, `uint32`, or `double`.

## Examples

collapse all

Read binary image into the workspace.

```BW = imread('text.png'); ```

Calculate the connected components, using `bwconncomp` .

```CC = bwconncomp(BW); ```

Create a label matrix, using `labelmatrix` .

```L = labelmatrix(CC); ```

For comparison, create a second label matrix, using `bwlabel` .

```L2 = bwlabel(BW); ```

View both label matrices in the workspace. Note that `labelmatrix` is more memory efficient than `bwlabel` , using the smallest numeric class necessary for the number of objects.

```whos L L2 ```
``` Name Size Bytes Class Attributes L 256x256 65536 uint8 L2 256x256 524288 double ```

Display the label matrix as an RGB image, using `label2rgb` .

```figure imshow(label2rgb(L)); ```

## See Also

#### Introduced in R2009a

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