USGS MIPS Imgstats Documentation

USGS MIPS Imgstats Documentation

This program is one of the XWindows applications that can be executed under the Applications pull-down menu in VISTA. IMGSTATS allows a user to interactively list the DN values of black-and-white or color composite images. Statistics such as the average, standard deviation, variance, median, skew, mode and range are calculated for the area listed and can be written to the print file IMGSTATS.PRT.

Obtaining statistics

There are two ways to obtain a listing within IMGSTATS, using the mouse or the keyboard. Using either method, a green crosshair will appear indicating the center line/sample coordinate from which IMGSTATS will obtain a listing and statistics.

Using the mouse, the user can click mouse button 1 anywhere inside the image(s) displayed or if a listing has already been obtained double clicking mouse button 1 on a DN value within the DN listing Window.

Using the keyboard, the user can enter the line/sample coordinate he/she wants to use as the center of the DN listing. To obtain a listing, type the line and sample coordinate into the text fields under "Line" and "Sample" and then click on the "Center of Window" button.

The listing is displayed in such a way that the selected pixels ' DN is highlighted and is displayed in the middle of Imgstats' listing window.

Note that after each listing, whether obtained via the mouse or the keyboard, the line and sample coordinates of the center DN will be displayed in these input boxes.

Statistics of color composites

When displaying a color composite, listings of each band can be obtained one at a time. The toggle buttons located in the "Listing" section, of the IMGSTATS dialog box, are used to select the channel from which the DN listing and statistical information are obtained. For example; if the Red Channel button is selected, IMGSTATS will display the information for the red channel. To display the information for one of the channels not currently selected, simply select the desired channel and IMGSTATS will automatically display the information for the desired channel. Note, if a black-and-white image is being displayed the "Listing" section will be stipled (greyed out) and unavailable to the user.

Statistical window size

The size of the window used to obtain the listing/statistics is user selectable. By moving the scroll bars in the "Window size" section, the desired information is automatically updated/redisplayed as the user selects new line or sample values. Currently, the minimum number of lines or samples is 1 and maximum number of lines or samples are 89, 63, and 45 for unsigned byte, signed word and floating point images, respectively. The window size is restricted to an odd number of lines and samples. The default window size is 5 lines by 5 samples.

Statistics and the print file

IMGSTATS provides the user with statistical information about the NxM window listed. In addition to the DNs being listed, the following information is also displayed as well as the center line/sample coordinate:

average
standard deviation
variance
median
skew
mode
range

Saving Results

Once a listing has been displayed, the user may save the statistical information obtained to the print file IMGSTATS.PRT. The name of the current image being listed, the size of the window, the center line/sample coordinate of the selection are also written to the print file. To save, simply select the "Save results" button and a dialog box is displayed. This dialog box allows the user to enter a label identifying the information to be saved. Note, if a label is not entered and the user selects the "OK" button, the desired information is not written to the print file. Note, "Save results" will be stipled (greyed out) and unavailable to the user until an initial listing is performed.

Exiting Imgstats

Selecting the "Exit" option from the pull-down menu will cause this program to terminate.

Examples

Below is a sample print file created by Imgstats.

****************************** imgstats ******************************

Execution date:  Fri Nov  1 16:24:18 1996


  Id label         : sample listing #1
  File Name        : dka100:[images]peak_tm1
  Window Size      : 5x5
  Center of Window : 387,893
  Center DN        : 80
  Average          : 80.0000
  Std Deviation    : 2.1909
  Variance         : 4.8000
  Median           : 80
  Skew             : 0.0000
  Mode             : 80
  Range            : 75 / 83


  Id label         : sample listing #2
  File Name        : dka100:[images]peak_tm1
  Window Size      : 15x15
  Center of Window : 787,215
  Center DN        : 103
  Average          : 103.2889
  Std Deviation    : 3.3148
  Variance         : 10.9877
  Median           : 103
  Skew             : 0.2615
  Mode             : 103
  Range            : 91 / 111


  Id label         : new image listing
  File Name        : dka100:[images]topo32
  Window Size      : 5x5
  Center of Window : 157,112
  Center DN        : -2.136e+06
  Average          : 3071382.8900
  Std Deviation    : 9259454.1378
  Variance         : 85737490930875.9840
  Median           : -2.136e+06
  Skew             : 1.6873
  Mode             : N/A
  Range            : -3.601e+06 / 3.088e+07

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