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Foundation :: Visualization and Virtual Reality :: DGX

DGX Documentation

Usage:  dgx    rmgfile            samples hgt_scale mag_scale expnt'
        dgx    magfile    dtefile samples hgt_scale mag_scale expnt'
        dgx -x magfile -y dtefile -z zvalue -z zvalue -z zvalue ...'

Where x and y are file format descriptors such as:

         i1 = byte              r4 = real*4          si2 = signed i*2
         i2 = integer*2         c4 = complex*4       c8 = complex*8
         i4 = integer*4         mag = real*4 mag file
         bs = byte swapped i2   dte = real*4 dte file

Where z is a display descriptor such as:

          s = samples                     h = hdr file name
          d = dte_scale                   f = look down factor
          m = mag_scale                   c = number of colors
          e = exponent                    F = flip x on
          l = start line                  S = display x slope on
          n = number of lines             P = memory backing on
          w = start height wrap           Z = zooms out by 4 at start
      x,  y = center samp,line at start   D = Full dynamic range
    lat,lon = center lat,lon at start

Where dte_scale = The number of units per color wrap [def=100 (360)]
Where mag_scale = The number of std deviations before saturation [def=2]
Where expnt = Power to raise data before displaying [def=1]

When two files are specified, the first file is assumed to be the amplitude data and the second file is height data unless specified explicitly with -mag or -dte.

Input parameters identified by dash descriptors can be entered in any order, including data file names.

A dash in any field except the width will result in the default value for that field.

The line, sample, height and magnitude of a pixel can be displayed by clicking on the desired pixel with the left mouse button. For files containing a Standard AIRSAR header or having an associated IFPROC header file, the pixel latitude and longitude can also be obtained by holding the space bar down while clicking.

To obtain a Zoom window of the region around a pixel, click on the pixel with the center mouse button. The zoom factor can then be adjusted by powers of 2 using the provided buttons. To select a new zoom region, use the center button to again click on a pixel in either window. The contents of the zoom window can be converted to Jpeg, PPM, or PostScript and saved to a file by clicking Print with the left, middle or right mouse buttons respectively.

If the number of colors are not specified, dgx will only allocate positions in the color table which are not currently in use. This preserves the window color when switching between applications, but when several programs are competing for the colors, there may not be enough left for dgx to run. Specifing the -c parameter enables dgx to allocate as many colors as desired so it can run and still maintain sufficient dynamic range in the display.

dgx has two ways to handle window updates. The default method only draws the visable portion of a window to the screen device. As the window is scrolled, the data shifting out of the visable region is discarded and the program grabs new data from disk to fill the exposed region. The advantage of this method is that it requires verly little memory at both the display client and server. The disadvantage is that it is slow to move around.

By specifing the -P flag, dgx loads an entire data set to be displayed into the local display device and shifts the job of updating the windows to it. This greatly increases the scroll speed but requires time upfront to transfer the image. It also requires enough memory in the local display to hold an 8 bit map of the image. No check of the memory size is made by dgx and it may crash if the available memory is not sufficient. Dgx's default display scheme maps data from the first pixel in the file to the the upper left corner of the display with sample number increasing from left to right across the screen and line number increasing from top to bottom down the screen. This mapping produces properly oriented images and dtes for left looking radar systems processed through the IFPROC or similiar processors. If the data is from a right looking sensor, or was processed on some other processor, it may require a flip in one direction to properly display it. The -F flag swaps the sample order so that the first pixel is in the upper right corner and samples increase from right to left.

When no amplitude data is available for a dte, the -S flag can be used to display a central difference slope estimate of the surface along with the height. The slopes give the appearance similiar to radar illumination from the left side of the screen and can make comparisons to radar data much easier.

If integer data files do not have a header but do require scaling for proper display of magnitude and height values, the following parameter descriptors can be specified along with their values:

            mm = mag multiplier    md = dte multiplier
            am = mag additive      ad = dte additive

To center the display on a particular pixel at startup, use the -x and -y descriptors, followed by the desired sample and line numbers respectively. If a header file is present, the image can also be positioned to a specific latitude and lonitude by using the -lat and -lon descriptors followed by the respective values in degrees.

Once the image is visible, the main window can be moved to a specific pixel location by clicking on the position label at the top of the window and entering the desired pixel in the dialog box. To select the center lat/lon, hold the space bar down while clicking on the label and enter the latitude and longitude in the dialog box.

To move the main window to the center of the zoom window, hold down the space bar and click on the zoom window with the middle mouse button.

To change the amplitude or height scaling while viewing the image, click on the amplitude of height selection button with the right mouse button and enter the new parameters in the dialog box.

For images with both amplitude and height, one can switch between the amplitude and the x slope by holding down the space bar and clicking the amplitude button.

Selecting the Amplitude or Height buttons with the left mouse button will switch back and forth between the displays quickly, but will use a reduced dynamic range. Using the center button will take longer, but will use the full color table. The default at startup is to use the reduce dynamic range, but this can be overriden by specifing -D on the command line at startup.

To display the slope of the amplitude data instead of the height, hold down the number 1 and click on the amplitude button. To get back to the slope of the height, hold the number 2 and click on the amplitude button.

To change the level of debug statements that are displayed during execution, use the -debug flag, followed by the a number. The value can range from 0 (for no debug info) to 6 (for the maximum info). The default value is 2.

To save the values returned by clicking on a pixel to the file click.dat, toggle with the "c" key in the image window. If a program name has been specified using the -clk flag, the program will be launched when you untoggle this feature.

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