Removing the background area of a raster layer using the Classified renderer

1. In the ArcMap table of contents, right-click the raster layer from which you want to remove the background and click Properties.
2. Click the Symbology tab and click Classified from the Show list.
3. Click the Classify button and click the Exclusion button on the Classification dialog box.

   The Data Exclusion Properties dialog box opens.

4. Click the Values tab and type the background value to be removed from the classification in the Excluded Values text box.

   The background value is removed from the classification and, therefore, will not be displayed.

5. If you want to show the excluded value in the legend, click the Legend tab and check the Show Color for Excluded Data check box.
   1. Choose a color to symbolize your excluded value and add a label and a more detailed description if you want.

      The description will only be displayed in the legend in a layout. The label will be attached to the excluded value symbol in the legend.