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Image Acquisitionand Proces

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Morphology 143<br />

I<br />

Closed<br />

{ }<br />

= Erode Dilate( ISource<br />

)<br />

Although performing two seemingly opposite morphs on the source image may<br />

suggest that it will result in the destination image being the same as the source, this<br />

is not the case. Original image data is lost on executing the Þrst operation, and hence<br />

the original image cannot be recovered.<br />

Dilate<br />

Þ<br />

Erode<br />

Þ<br />

As you can see, the small inner holes were Þlled, as was a portion of the upper<br />

inlet.<br />

6.1.4 OPENING<br />

Opening an image (expanding holes and other background features in an image)<br />

requires the opposite sequence to closing: Þrst erode the source image, and then<br />

dilate it:<br />

I<br />

Opened<br />

{ }<br />

= Dilate Erode( ISource<br />

)<br />

Erode<br />

Þ<br />

Dilate<br />

Þ<br />

The opened image may not look much like its source, although the thinner<br />

portions of the object have been successfully opened, and only the bulk area remains.<br />

6.1.5 NONBINARY MORPHOLOGY<br />

Although the simplest method of morphology is to Þrst threshold an image, creating<br />

a binary image (a pixel is either light or dark — there is no in-between), other<br />

methods exist such as gray and color morphology.<br />

Gray morphology is achieved by considering each of the neighboring colors as<br />

binary couples, and performing binary morphology between them. This process is

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