6.1.5 Drawing the Subregion Parameter

Prior to executing the Write Subregion to File function available in the File menu, it is necessary to define a polygon on the screen that encloses the desired subset of image points to be written to the new file. This task may be accomplished by holding down the SHIFT key on the keyboard and clicking the left mouse button at each vertex of the desired polygon. Click the right button to automatically close the polygon. Clicking the left button again after closing the polygon erases it and starts a new polygon.