
XPRISM2(INPUT_FILE)          Khoros           XPRISM2(INPUT_FILE)

     VIFF INPUT FILE

     A VIFF input file is the image file format used by KHOROS.
     It is comprised of a header that contains all of the neces-
     sary information about the image file, followed by the data.
     A VIFF file may be broken down into an IMPLICIT or EXPLICIT
     file.  An IMPLICIT file contains Y data, with the location
     information (ie. X axis) implied from the data itself.  An
     EXPLICIT file contains the data as well as the specific
     location information.  A more detailed description of IMPLI-
     CIT and EXPLICIT files and their use is provided below.
     Xprism2 is capable of handling all VIFF image data storage
     formats except BIT, and is capable of handling multiband
     images.

     Input of IMPLICIT Image Files

     In the course of image processing, the user may want to plot
     a single column or a single row of pixel values; this can be
     done using the 2D plot capability of xprism2.  In prepara-
     tion for this operation, a image or sub-image consisting of
     a single row or column must be created before beginning the
     session with xprism2 (see man pages on vextract).  Alterna-
     tively, the user may wish to create a 2D plot of a typical
     image or subimage that is square or rectangular.

     To accomodate the possibilities in each case, each of these
     three categories of images are acceptable for plotting in
     2D.  The image used may have 1 row, 1 column, or a variable
     number of rows and columns. If, however, the attempt is made
     to plot an image with 0 rows or  0 columns, xprism2 will
     print an error message, as this implies insufficient data to
     create any sort of plot.

     If the column size of the image is 1 (i.e., the image con-
     sists of a single row), xprism2 will create a 2D plot where
     the X Axis represents the index of each pixel in the row,
     and the Y Axis represents the value of each pixel.  Simi-
     larly, if the row size of the image is 1 (i.e., the image
     consists of a single column), xprism2 will create a 2D plot
     where the X Axis represents the index of each pixel in the
     column, and again, the Y Axis represents the value of each
     pixel.

     When a "normal" image is plotted in two dimensions, (that
     is, an image with more than one row and more than one
     column) the following procedure is utilized by xprism2 to
     create the 2D plot.  Each scanline of data of the image,
     from top to bottom, is interpreted as contiguous plot data;
     scanlines of pixels are plotted end to end as a single
     series of points.  Thus, when viewing a square or rectangu-
     lar image as a 2D plot, the X axis includes all rows and
     columns of image data, while the Y axis represents the pixel
     values at each pixel position.

     To plot an Implicit Image File, fill in the "Filename"
     parameter box with the desired filename (for more informa-
     tion, see the help on the Environment Pane), and click on
     the "PLOT FILE" action button.  The implicit image file will
     be read in, interpreted as described above,  and displayed
     according to the current value of the "plot type" toggle.

     Input of EXPLICIT Image Files

     Explicit Image Files may also be used as input to xprism2;
     in this case, the X and Y data is explicitly stated, so
     there is no interpretation to be done as is the case with an
     Implicit Image file.  The X coordinates come directly from
     the location data; the Y coordinates come from the image
     data.

     Saving a plot as an Explicit Image File (see help on the
     "Files" pane on the "Output" subform) implies that it can be
     exactly reproduced whenever it is used as input to xprism2,
     since the data points are saved explicitly.

     Note, however, that plot attributes such as labels, colors,
     fonts, line types, etc. cannot be saved in either Implicit
     or Explicit Image File Format, as these attributes have no
     storage place in an image file. Any time a plot is saved as
     an image and later re-displayed, any of these attributes
     will have to be re-set to the desired values.

     To plot an Explicit Image File, fill in the "Filename"
     parameter box with the desired filename (for more informa-
     tion, see the help on the Environment Pane), and click on
     the "PLOT FILE" action button.  The explicit image file will
     be read in and displayed according to the current value of
     the "plot type" toggle.

     The number of points to be displayed in the workspace may be
     controlled by changing the "step size", "begin" and "end"
     data points.  Note that this does not change the data in the
     file, but only how the data is displayed in the workspace.

     Multiband and Complex Data Images

     Xprism2 is capable of handleing multiband VIFF images and
     images of all data types except BIT. When a multiband VIFF
     image is read in, a list of bands will pop up. The user must
     select the desired band to plot. To plot more than one band,
     one must read the image in again and select the desired
     band. When a VIFF image has a data storage type of COMPLEX,
     a list asking which complex type to plot pops up. The user
     must select the desired complex plot type. Currently one can
     choose to plot the Real part, the Imaginary part, the Magni-
     tude or the Phase. Xprism2 uses lvctor to convert the com-
     plex type. For more information in this conversion process
     see vctor(1) or lvctor(3).

     Copyright 1991, University of New Mexico. All rights
     reserved.

Khoros                    Release: 1.0                          1

