Each scatter plot is a combination of the histograms of two channels showing the correlation between these histograms. The resulting window is 256 x 256 pixels, with the bottom left pixel representing the number of pixels that are zero in both channels. The top left pixel represents the number of pixels that are 255 in the first channel and 0 in the second. Similarly the bottom right pixel would represent the number of pixels that are 255 in the second channel and 0 in the first. In the case of images that have a range greater than from 0 to 255, the imagery will be scaled to fit the 256 value range.
The brightness of each scatter plot pixel is determined by the number of pixels in the source image with the corresponding grey level values. Thus, bright areas indicate common combinations and black areas indicate combinations that virtually never occur. Typically, the scatter plot will consist of a bright smear in one area of the scatter plot. The frequency may be displayed either using a simple grayscale or it may be displayed using a Pseudo-color table.
To better view the area of interest, it is possible to use the ``control-left'' and ``control-right'' mouse combinations to zoom in and zoom out respectively. It is also possible zoom in by dragging out a rectangular view area in the graph. The "Show All" button at the button will display the entire graph.
Along with the scatter plot, the class list is also displayed, which will allow you to selectively control which class means and ellipses are to be displayed. Simply click either in the Plot Mean or Plot Ellipse column to display the mean or ellipse for a particular class. Clicking in the column header will display a pop-up menu which allows you to quickly plot all, none, or only the highlighted classes' means and/or ellipses.
Five buttons can be found at the bottom of the panel. They are: