Dilating an Image :: Morphological Operations (Image Processing Toolbox User's Guide)

Image Processing Toolbox User's Guide

Dilating an Image

To dilate an image, use the imdilate function. The imdilate function accepts two primary arguments:

The input image to be processed (grayscale, binary, or packed binary image)
A structuring element object, returned by the strel function, or a binary matrix defining the neighborhood of a structuring element

imdilate also accepts two optional arguments: PADOPT and PACKOPT. The PADOPT argument affects the size of the output image. The PACKOPT argument identifies the input image as packed binary. (Packing is a method of compressing binary images that can speed up the processing of the image. See the bwpack reference page for information.)

This example dilates a simple binary image containing one rectangular object.

BW = zeros(9,10);
BW(4:6,4:7) = 1
BW = 
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     1     1     1     1     0     0     0
     0     0     0     1     1     1     1     0     0     0
     0     0     0     1     1     1     1     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0

To expand all sides of the foreground component, the example uses a 3-by-3 square structuring element object. (For more information about using the strel function, see Structuring Elements.)

SE = strel('square',3)
SE =
 
Flat STREL object containing 3 neighbors.

Neighborhood:
     1     1     1
     1     1     1
     1     1     1

To dilate the image, pass the image BW and the structuring element SE to the imdilate function. Note how dilation adds a rank of 1's to all sides of the foreground object.

```
BW2 = imdilate(BW,SE)
```

Structuring Elements Eroding an Image