Use Overlay Classes to produce an image map with a color composite or gray scale background image and the classes overlaid in color. ENVI creates a three-band RGB image.

Due to the nature of the classification overlay, the background image should be stretched and saved to byte output images prior to overlay.

1. From the Toolbox, select Classification > Post Classification > Overlay Classes. The Classification Input File dialog appears.
2. Select the classification image and any optional spatial subsetting, then click OK. The Input Background RGB Input Bands dialog appears.
3. Click sequentially on the red, green, and blue bands to use for the background image. The input files must be byte images (that is, files containing values between 0 and 255). If a gray scale background is desired, select the same spectral band for the RGB inputs.
4. Click OK. The Class Overlay to RGB Parameters dialog appears.
5. Select the classes to overlay on the background image by clicking the toggle button associated with the class name in the list.
6. Select output to File or Memory.
7. Click OK. ENVI creates the class overlay image. If your display is set to 8-bit color, the class overlay image may appear incorrect when displayed due to the color quantization. However, on output, it will be correct.