Remove Null Value from Image Layer

To set properties for a Remove Null Value polygon on an Image layer:

1.     Above the Working Window, click the Image tab and from the Layer List, select an Image layer.

2.     Do one of the following:

§  Create a Null Value Polygon/Rectangle. See “Creating Polygons and Rectangles” in this chapter for more information.

§  Select an existing polygon. See “Selecting a Polygon or Rectangle” in this chapter for more information.

3.     On the Polygon Edit tab, in the General group, from the Operation Type drop-down list, select Null Value Polygon/Null Value Rectangle.

Note:        This option will already be selected if the polygon was initially created as a Null Value polygon.

4.     On the Polygon Edit tab, in the General group, from the Apply Operation drop-down list select Inside Shape or Outside Shape.

5.     In the Null Value group, click the arrow next to the Null Color command and select the required Null color from the drop-down list of colors.

Note:        If you want more color options than appear in the Null Color drop-down list, click More Colors, and select the required color from the Colors dialog box. If a null value was provided with a source, it is recommended to enter the parameters into the value boxes in the Colors dialog box. See "Colors Dialog Box" in this chapter for more information.

6.     In the Tolerance field, enter the permissible deviation from the specified value when the color value is irregular. The color value specified is removed from the area the polygon applies to.