USGS MIPS Hstgrm Documentation

USGS MIPS Hstgrm Documentation

This program uses the X windows system to display a graphical histogram of an

Obtaining a histogram

To obtain a histogram of an image, select the "Open" item from the file pull-down menu. This will generate a file selection box that can be used to select the desired image file.

Options in creating a histogram

Selecting the "Options" item from the file pull-down menu will allow the user to select how information is collected from the image. The line and sample increments are used to sub-sample the image and will reduce the amount of time required to generate/compute the histogram for extremely large images.

The minimum and maximum DN values are used to specify the valid range of DNs that are to be used when computing statistical information. For example, the statistics (average, etc.) from an image containing a large border of zeroes would be seriously effected by the zeroes if they where included. However, by setting the minimum valid DN to one the statistics will not be affected by the zereos.

The histogram

The graphical histogram of the image will be displayed in the upper-left window. It will be shown in red with a black background. The DNs represented in the histogram range from 0 on the left side of the window to 255 on the right side of the window.

Also, if the pointer is moved into this window and mouse button one is pressed and held down, the Histogram Information window (directly below the graphical histogram) will be scrolled to the DN beneath the pointer.

Statistics Information

The Statistical Information window will be displayed on the right side and contains statistics about the image including:

Average
Median
Mode
Standard Deviation
Variance
Skew

In addition the total number of DNs in the histogram, the total number of DNs outside the valid minimum/maximum range, and a full and statistical range of DNs are given. The full range is found by searching from the ends of the histogram until a DN with a non-zero frequency is found. The statistical range is found by searching from the ends of the histogram until the 0.5 and 99.5 cumulative percentages are found.

Histogram Information

The Histogram information window is on the bottom-left side (below the Graphical Histogram) and contains detailed information about the histogram including:

Frequency of each DN
Percentage of each DN
Cumulative percentage

Exiting Hstgrm

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

Examples

This is a screen dump of Hstgrm.