WELCOME TO THE IMAGE PROCESSING DEMO


   Image processing can improve the way an image
   looks.  Image-processed data, or a processed
   image helps you distinguish and recognize more
   subtle characteristics of the original image.


   MENU OPTIONS
   ------------

   File Menu:
      Select "Quit" to exit the Image Processing
      Demo and return to the IDL Demo main screen.

   About Menu:
      Select "About image processing" for
      information about the Image Processing Demo.


   FEATURES
   --------
      IDL offers several ways to process an image,
      some of which are introduced below:


      o  Zooming
         
         Smaller sub-sections of large datasets can
         be manipulated. The image shown here is an
         aerial view of New York City. A section of
         lower Manhattan is enlarged using the
         REBIN function on a subscripted section of
         the original image array.

         To reposition the zooming area, click your
         mouse on the area you would like to see
         more closely.


      o  Fourier filtering

         IDL's Fast Fourier Transform (FFT)
         function can process vectors and 2D array
         in either forward or reverse.

         <<Filter width>> slider
         Selects the filter width. A higher filter
         width gives the filtered image higher
         resolution.


      o  Pixel scaling

         The BYTSCL (byte scale) command scales
         pixel values into the range of available
         colors.

         <<Minimum>> slider
         You can specify the minimum byte value
         allowed in the reconstructed image.

         <<Maximum>> slider
         You can specify the maximum byte value
         allowed in the reconstructed image.


      o  Histogram

         Histogram equalization can be used to
         change the visible contrast of an image.

         <<Minimum>> slider
         You can specify the minimum byte value
         allowed in the reconstructed image.

         <<Maximum>> slider
         You can specify the maximum byte value
         allowed in the reconstructed image.

 
      o  Edges

         The SOBEL function performs edge
         enhancement on an images.

         <<Smooth width>> slider
         Sets the width of the smoothing function.
         A higher width produces a reconstructed
         image with lower resolution.


      o  Dilate and Erode

	 IDL's Dilate and Erode functions operate
	 on shapes within an image.

	 In this example, before we start dilating
	 and eroding, a threshold mask is derived
	 from the grayscale intensities in the
	 image.  All values less than a given
	 percent of the image's maximum intensity
	 are masked.

         <<Break Mask>>
	 Click this button to Erode and then Dilate
	 the shape of the mask.  This has the
	 effect of "breaking off" details in the
	 mask's shape.  This operation is known
         as Binary Morphological Opening.

         <<Fuse Mask>>
	 Click this button to Dilate and then Erode
	 the shape of the mask.  This has the
	 effect of "fusing together" parts of the
	 mask's shape.  This operation is known
         as Binary Morphological Closing.

	 <<Neighborhood Mins.>> 
	 Click this button to perform grayscale
	 erode and then grayscale dilate on the
	 image itself, where masked.  This yields
	 neighborhood minimums in the masked
	 regions of the image.  Thus bridges and
	 other details are removed.  This operation
	 is known as Grayscale Morphological
	 Opening.


      o  Convolution

         Convolutions may be performed on arrays of
         1, 2, and 3 dimensions. This screen shows
         the effects of convolving an image with a
         kernel.

         Use your left mouse button to click on the
         squares of the kernel grid, toggling them
         on or off.

         <<CONVOLVE>> button
         Computes and displays the convolved
         image.