|  | The Polygon tool allows you to move any corner any way you want, and add 
      corners by Shift-clicking on a line (and delete corners by Ctrl-clicking 
      a node). Note there are two sets of handles with this tool – the inner 
      handles directly move the mask corners, varying the length of the two sides 
      as needed while the outer handles shift the mask maintaining the relative 
      lengths of the two sides nearest the handle. There is also a center handle 
      that shifts the whole mask without changing its shape.
 In this image, the nonrectangular shape is slight, but more extreme geometries 
      with straight edges can easily be fit with this tool. When the polygon (or 
      whichever geometrical tool-shape you’ve used) fits the way you want, 
      click the Apply button in the lower left corner to make a mask . . .
 
 
   
 Note the mask can be shown as a transparent or solid color over the image
       (red, green, blue or white), turned off, or only the mask can be shown
      in  B&W (using the appropriate two buttons on the right side of the
      Mask  window, directly below the Area and Undo buttons). You can “undo” 
      the last mask step and add additional sections using any of the mask tools
       until the mask is complete. When the mask is ready, clicking the OK button
       at the upper right of the mask window will create a new image window with
       only the mask. This can be saved as a file, or used temporarily with its
       associated image file. In addition, you can directly use the mask above
       with various Picture Window Pro tools and functions, but saving it first
       is a good idea in case you want to make different modifications to the
      same  image in the future . . .
 
 
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