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This subform allows the user to perform pixel thresholding and/or 
pixel windowing operations. 
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1)  Pixel Windowing
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Pixel windowing is used to mask out certain parts of the image so that
only a desired range of pixels is observed.  Pixel windowing works by
allowing a windowed region of the original pixel values to be displayed.
The user selects the pixel value of the masked region; all values outside
the windowed region will be set to this masked region pixel value. 
If the masked region pixel value does not exist in the colormap, 
the corresponding grey level value will be used.
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In order to make sure that none if the other \fBeditimage\fP features 
(specifically, pseudocolor or lut) over-ride this threshold, we set the 
pixel's histogram
to zero.  None of the other \fBeditimage\fP features will be able to update 
these pixels with new values, until the histogram is restored.
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.IP "a)  Use of the Scroll Bars with Pixel Windowing"
The desired range of pixels to be observed is set using the scroll bars that
appear at the bottom of the Threshold/Windowing subform. The top scroll bar
sets the lower end of the desired pixel range;  the bottom scroll bar sets
the upper end of the desired pixel range.  The value boxes to the right of each
scroll bar displays the values to which the lower and upper pixels of
the range are set.  
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.IP "b)  The Masked Region Pixel Value"
This is the pixel value used in the masked regions. 
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.IP "c)  The Windowed Region - accept/reject"
If the windowed region is set to "accept", the original pixel values between
the values set by the lower scroll bar and the upper scroll bar will be 
displayed;  this can be thought of as a bandpass filter.  If the windowed 
region is set to "reject",  the original pixel values \fIoutside\fP the 
region defined by the lower and upper scroll bars will be displayed; this
can be thought of as a bandreject filter.
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.IP "d)  The Color Strip"
The color strip above the scroll bars displays the region windowed and 
masked, based on the lower and upper scroll bar positions.
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2)  Pixel Thresholding
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Pixel thresholding is used to perform real-time image thresholding.
It generates a binary (or 2 pixel value) image.  Pixel thresholding works by
assigning a non-zero pixel value to the selected region; the rest of the image
will be turned black.  
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.IP "a)  Use of the Scroll Bars with Pixel Thresholding"
The desired range of pixels to be thresholded is set using the scroll bars that
appear at the bottom of the Threshold/Windowing subform. The top scroll bar
sets the lower end of the desired pixel range;  the bottom scroll bar sets
the upper end of the desired pixel range.  The value boxes to the right of each
scroll bar displays the values to which the lower and upper pixels of
the range are set.  
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.IP "b)  The Non-Zero Pixel Value"
This is the pixel value assigned to the all the pixels within the range defined
by the scroll bars.  Note that pixels outside this range will appear black.
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.IP "c)  The Threshold Region - non-inverted/inverted"
If the threshold region is set to "non-inverted", the non-zero pixel value
will be displayed between the limits set by the lower scroll bar and the 
upper scroll bar;  the rest of the image will be black.  If the threshold region
is set to "inverted",  the non-zero pixel value will be displayed outside the 
limits set by the lower scroll bar and the upper scroll bar.
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.IP "d)  The Color Strip"
The color strip above the scroll bars displays the thresholded region 
based on the lower and upper scroll bar positions.
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Reset
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Clicking on the "RESET" button will re-set the currently displayed image
to it's original state when the Windowing/Thresholding subform was entered
for the first time. 
