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        example programs using the region-of-interest capabilities
                            of the image object

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01.roi_rect/

   This program puts up an image object displaying the entire image; it
   also creates a smaller image object to the lower right in which a region
   of interest can be displayed.

   A button is created, labeled "Extract Region of Interest".  When you click
   on the button, a callback installed on the button allows you to rubber-band
   a rectangle about the desired region of interest;  that region of interest
   will then be displayed in the smaller image object to the lower right.

02.roi_event/

   Similar to example 01, this program puts up an image object displaying
   the entire image; it creates a smaller image object to the lower left
   in which a region of interest can be displayed.  You can rubberband
   regions of interest in the image, and the smaller image on the bottom
   will be updated with the latest region of interest.

   After the image is displayed, rubberband the area of interest by
   clicking in the image (the cursor will change to the "hand") and dragging
   the mouse so that the desired region of interest is outlined.
   When you release the button, the smaller image on the bottom will be
   immediately updated with the region of interest.  This process may
   be repeated as many times as desired.

03.roi_zoom/

   This program puts up an image object displaying the entire image; it
   also creates a zoom object that is updated on button press in the image.
   
   First, click in the image to position the zoomed portion of the image
   in the zoom window.  Then, draw a polyline in the zoom window outlining
   the irregular region of interest, which will be displayed in the small
   image window to the lower right.

04.roi_shape/

   This program puts up an image object displaying the entire image; it
   also creates a smaller image object in which a region of interest can
   be displayed.
  
   As each Region of Interest is extracted, the shape type is incremented.
   This causes the user to cycle thru the different types of extraction
   shapes.
