Use Buffer Zone Image to create a buffer zone image from a classified image. In the buffer zone image every pixel has a floating-point or integer value that is defined as the distance from that pixel to the nearest pixel of the selected class or classes in units of pixels. You designate a maximum distance value and the result is that any pixels with a distance larger than that value will be set to the maximum distance value.

You can also write a script to create buffer zone images using the BufferZone task.

  1. From the Toolbox, select Classification > Post Classification > Buffer Zone Image. The Classification Input File dialog appears.
  2. Select the input classification file and any optional spatial subsetting, then click OK. The Buffer Zone dialog appears.
  3. From the Class Names list, select the classs to measure the distance to. If more than one class is selected, the distance will be from the pixel to the nearest class.
  4. From the Output Data Type drop-down list, select Integer or Float.
  5. Click the Maximum Distance increase/decrease buttons to set the maximum distance to measure, or type the value (in pixels) into the corresponding field. Any pixels with a distance larger than this value will be set to the maximum distance value.
  6. Select an output filename and folder in the Output Raster field.
  7. Enable the Preview check box to preview the settings before processing the data. The preview is calculated only on the area in the view and uses the resolution level at which you are viewing the image. To preview a different area in your image, pan and zoom to the area of interest and re-enable the Preview option. Depending on the algorithm being used by the tool, the preview result might be different from the final result of processing on the full extent, full resolution of the input image in the following scenarios: 1) If you zoomed out of the input raster in the view by 50%, or a percentage less than 50%, ENVI uses a downsampled image at the closest resolution level to calculate the preview, or 2) If the entire image is not visible in the view, ENVI uses the subset in the viewable area of the input image to calculate the preview.

  8. Enable the Display result check box to display the output in the view when processing is complete. Otherwise, if the check box is disabled, the result can be loaded from the Data Manager.

  9. To reuse these task settings in future ENVI sessions, save them to a file. Click the down arrow next to the OK button , select Save Parameter Values, then specify the path and filename to save to. Note that some parameter types, such as rasters, vectors, and ROIs, will not be saved with the file. To apply the saved task settings, click the down arrow and select Restore Parameter Values, then select the file where you previously saved your settings.

  10. You can run the process in the background on your computer or in the background on an ENVI Server (if available). Click the down arrow next to the OK button and select one of the following:

    • Run Task in the Background: Runs the process on your computer. This method does not use an ENVI Server. The job progress will show in the ENVI Job Console's Background Jobs tab.
    • Run Task on envi_server_name. Runs the process on the selected ENVI Server. The job progress will show in the ENVI Job Console's envi_server_name tab.

    See ENVI Job Console for details on monitoring ENVI Server jobs and viewing results. See ENVI Servers for details on configuring and using an ENVI Server.

  11. Click OK.