Use Edit Polygon to select irregular polygon areas in an image file. This allows you to:
Select data for 3D models or volume projections.
Copy selected data to another file.
Get statistics for selected areas.
Edit polygon provides tools that you can use:
You can define the parameters for the Guided Select polygon creation mode. When you choose a point on the image, it "snaps" to the nearest pixel that matches the specified parameters.
On the Edit Polygon dialog box, choose Options | Guided Mode Options to open the Guided Polygon Select Parameters dialog box.
Select one of the following methods for choosing pixels in the Guide Method option list:
Maximum Gradient chooses the pixel whose intensity is the most different from that of its neighbors.
Threshold chooses the pixel whose intensity is closest to the guide threshold for the current wavelength.
In the Guide Box field, enter the size of the area (in pixels) to be searched (this value must be an odd number).
To prevent selection of outlaying points, select Weight Center of Box More.
In the Guide Thresholds fields, specify the intensity value that the guided selection snaps to for each wavelength.