C77 Morphological Processing

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Morphological processes are not the usual stock-in-trade of astronomical image processing, but some of them do have their uses from time to time. AIP4Win provides a whole suite of these functions, the most useful of which are the feature-detection operators. In this tutorial, we will explore several of those functions. However, the Contour Map is probably the most fun. Our test image shows the Whirlpool Galaxy, M51.

Step 1: Load the Image. Load the image file "m51.fts" from the Image Enhancement subdirectory of the Tutorial directory on the CD-ROM. Check the Auto button on the Image Display Control to make sure the image is fully stretched.

Step 2: Invoke and Setup the Contour Map Tool. Click the Enhance I Morphological Operations I Contour Mapping... menu item to bring up the Con tour Map Tool. There are two mapping options: Outline Regions of Equal Area, or One Contour Line at a Given Pixel Value. Select the first one, which will create a display like a topographic map. There is a slider/text box labelled How Many Contour Lines?. The more lines you have, the longer the map will take to generate. For a slow PC, this can be quite a while. For this example, pick 5 (unless you have a fast machine; then, choose 10).

Step 3: Create the Contour Map. Click the Apply button and a window will pop up that shows the status of the mapping operation. When it is done, a new image will appear containing the contour map of the original image.

Step 4: Adjust the Display. You can use the Image Display Control to remove the gray sky background by increasing the Black value until the background darkens. What you are doing here is to turn off the contour lines around the background image noise.

Step 5: Blur the Original Image. Click on the original image, and then invoke the Blur Tool by clicking on the Enhance I Blur... menu item. We will use the Blur Tool to apply a Gaussian blur to the image to smooth it. This will reduce the jaggedness of the contour lines.

Select a Radius of 3 pixels, click Apply, and a fuzzy version of M51 will be created.

Step 6: Rerun the Contour Map. Invoke the Contour Map Tool and set it up as in Step 3, but this time using the blurred version of the image, and click Apply. You will notice that the contour lines are much smoother in the resulting map.

Experiment with the various settings and try resampling the image to 200% (resample using Transform] Re sample). This will leave more room for the contour lines in the map. Close all open images when you are done.

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