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        example programs using the colorcell object

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1.colorcell_display/

  This program creates an image object which displays the kitten image.
  Then, a colorcell object is created. A colorcell object is associated with
  a pixel value in an image; it is a box filled with the color in which
  the pixel appears, and labelled with the pixel value.
 
  An event handler is installed which allows you to click the mouse in
  the image;  the colorcell object will be updated with the color and
  value of the pixel on which the mouse was clicked.

2.colorcell_update/

  Like the first example, this program creates an image object which displays 
  the kitten image, and then creates a colorcell object.  The event handler
  which is installed for button press in the image will register the value 
  of the first pixel that you click on.  Further button press events in the
  image will cause pixels to take on the same color as the first pixel.
 
  The "restore" button will restore the pixels to their original colors;
  the "clear" button will allow you to start the process again.

3.colorcell_set/

  This example demonstrates how the XVW_COLORCELL_REDVAL,
  XVW_COLORCELL_GREENVAL, and XVW_COLORCELL_BLUEVAL attributes
  can be used to change pixels in an image to be a particular color specified
  by its Red, Green, and Blue components.
 
  Like the first & second examples, this program creates an image object
  which displays the kitten image, and then creates a colorcell object.
  The colorcell object is hardwired to reflect the color of pixel value 50.
 
  The "set" button will pop up a query object which allows you to enter,
  values for red, green, and blue.  All pixels with value 50 will then
  change to be the color specified.
 
  The "restore" button will restore pixel 50 to its original color.

4.colorcell_delete/

  This example demonstrates how the XVW_COLORCELL_DELETE attribute
  can be used to change restore pixels in an image to their original
  color after they've been changed to a new color specified
  by its Red, Green, and Blue components.
 
  Like the first example, this program creates an image object which displays
  the kitten image, and then creates a colorcell object.
 
  When the "set red" button is clicked on, a number of the pixels in the
  image are colored red.  The event handler
  which is installed for button motion in the image will delete the pixels
  from the colorcell list, restoring them to their original values as the
  user moves the pointer across the image, keeping the button down.

5. colorcell_highlight/

   This example demonstrates how the colorcell object can be used to
   interactively change colors of pixels in an image.
  
   An image is created, with "restore" and "quit" buttons to the upper left,
   and a colorcell object to the upper right.
  
   As the user moves the pointer across the image, an event handler gets the
   value of the pixel at that point and adds it to the list of indexes used
   by the colorcell (the value of the last pixel is deleted, so that the
   colorcell list contains only one index at any given time).  The RGB values
   being displayed for that pixel are then obtained from the colorcell, and
   are reversed with a simple (255 - x) algorithm.  The new RGB values are
   then set on the colorcell.  This procedure has the effect of "highlighting"
   all the pixels in the image that have the same value as the pixel under the
   pointer.
  
   The "restore" button restores the original colors of the image, and
   the "quit" button quits the program.

