Use the Top Hat Dark filter to have differences between the source image and the resulting image displayed after the Close morphological filter operation has been performed.
You'll find the filter in the Process > Morphological Filter menu.
See also
Overview - Morphological Filter
Working with morphological filters
Settings for the filter
Here, you can find information on how you can set the shape and size of the morphological filter. The dialog box that is opened when you use an image processing operation is made up in the same way for every operation. Click here to switch to a description of this dialog box.
Application
The Top Hat Dark filter's resulting image contains exclusively the image segments that have been added to by the Close morphological filter. This can be holes in the objects or the cleaning up of fuzzy edges on the objects. The filter thus makes it possible to check the quality of the image that is on display. Because the pixels that were filtered out correspond to image defects, the filter results can be used to control whether the image meets the acceptation conditions.
The illustration demonstrates the way the filter works on a simple structure: The source image (1) shows the original structure. After the filtering with the Top Hat Dark filter has taken place, the image (3) shows only those pixels that differentiate the source image from the one that has been cleaned up by applying the Close morphological filter (2 ). In the image (4) the pixels that were removed by the Close filter are shown in black.
Exactly what happens?
This filter is a combination of the Close morphological filter and an arithmetic subtraction. First, the Close filter is applied to the source image. The results of this filter operation are subtracted from the source image. The resulting image is dark and the pixels that were changed by the Close morphological filter operation remain bright.
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