
Editimage(Display Utils)     Khoros      Editimage(Display Utils)

     Interactive Look Up Table

     The LUT subform provides a graphical representation of how
     the primaries are mapped to the image pixel values; the
     shapes of these primary color curves can be interactively
     changed by the user.

     The "LUT" window displays three LUT plots, each of which has
     a vertical axis which represents the range of image pixel
     values, and whose horizontal axis corresponds to the values
     of one of the three display colors.  The minimum and maximum
     values for each axis are given, along with boxes that numer-
     ically show the current mouse cursor position with respect
     to each axis.

     Using Interactive LUT to Alter the Look Up Table

     Changing the look up table is an easy process.  Position the
     cursor in the plot window which is labeled with the desired
     color. Large white crosshairs will mark the position of the
     mouse in the window, indicating that that you are ready to
     change the values of the primary color curve displayed in
     that plot. Click once at the position where you wish to
     begin changing the color curve. This marks the beginning of
     the segment of the color curve that you wish to change.  The
     color curve will follow the mouse as it is moved within the
     plot window; as you move the mouse back over the same range,
     the original curve will be restored. While the process is in
     action, the currently displayed image will immediately
     reflect changes to the color curve.

     When the segment of the color curve appears as desired,
     click again.  A straight line will be drawn from the first
     point to the second, and the changed segment of the curve
     will be "set" at that point. Now, the process is repeated,
     until the color ramp for that primary appears as desired.
     When finished, click the mouse twice at precisely the same
     point.  The large white crosshairs will appear again, indi-
     cating that you are now finished with that color curve.  At
     this time, you may go on to change one of the other two
     color curves, or to exit LUT.

     To determine how a pixel value is mapped using the "LUT"
     window, locate the image pixel value on the vertical axis by
     positioning the horizontal cross hair at the pixel value and
     then project across until it intersects a color curve.  The
     point on the horizontal axis where this intersection occurs
     is the value for that display color that is mapped to the
     image pixel value.  This can be done for all three parts of
     the current colorspace.  For grey level images, all three
     colors will follow the same curve.

     Undoing Changes

     At any point, the "UNDO" button may be pressed, undoing the
     latest change to a color segment.  Since all color changes
     are kept in a stack, the "UNDO" button will simply pop the
     stack; this implies that successive clicks on "UNDO" will
     eventually restore the color curve to its original state.
     Warning:  Since all colormap operations are tied together,
     "Undo" will also reverse color changes made using "Pseu-
     doColor" or "Windowing/Thresholding".

     Histograms

     If desired, a histogram which shows the distribution of the
     image pixel values may be plotted in the same window as the
     colormap.  The default action is to display the histogram.
     If no histograms are desired, click on the logical "Histo-
     gram" logical selection so that "Shown" changes to "Hidden".

     When a histogram is displayed, three types of histograms are
     available. The histogram type may be continuous, filled, or
     discrete.  Toggle the "Histogram Type" cycle option until
     the desired histogram type is displayed.

     For the histogram plot, the horizontal axis represents the
     image pixel values and the vertical axis represents the
     number of occurrances.  Disregard the values on the vertical
     axis when examining the histogram since they apply only to
     the colormap plot.

     Colorspace Models

     The LUT function may use any one of eight color systems
     available with editimage: RGB, CMY, HSV, HSL, YIQ, XYZ, UVW,
     or GREY.  One can change the current colorspace model that
     is used with the LUT function by clicking on the desired
     colorspace model.  The three plots which represent the
     colormaps for each of the three colors of the chosen color
     system will update immediately when the colorspace model is
     changed. WARNING: if the color curves in LUT are initially
     changed in one colorspace, and later the colorspace model is
     changed, it is IMPERATIVE that the user be aware of the
     relationship between the former colorspace and the latter
     colorspace.  If color curves are set in the first
     colorspace, and further changes to the color curve are made
     in a second colorspace over a region which is undefined in
     the second space with respect to the first, the color curves
     exhibited in the plot windows will exhibit erratic and
     unpredictable behavior.  This is to be expected.  For a
     detailed explanation of each colorspace model, see the sec-
     tion on "Colorspaces".

     Copyright 1992, University of New Mexico. All rights
     reserved.

Khoros                    Release: 1.0                          1

