Image Enhancement

Another way to look for information in an image is to adjust the contrast in the image. This does not change the values in the image, but simply adjusts the colors associated with those values. We have displayed this image with no stretch, and you can see it is somewhat darker than we would like.

One way to improve this situation is to apply a Two Standard Deviation Stretch to the image. This method of displaying data ignores the highest and lowest values so that more detail can be assigned to the areas in between.

Another method of displaying the data is the Histogram Equalization method. This method assigns more color bins to pixel values that occur more frequently.

1. In order to change the display to Histogram Equalization, click Image on the toolbar, and choose Histogram Equalization, or click on the histogram equalization icon icon.


2. What changes take place in the data? Notice that differences within fields are enhanced.


3. To change to the Two Standard Deviation Stretch use the two standard deviation stretch icon icon. This display is the easiest for us to interpret, so we will use this display for the remainder of the tutorial.