Use Classification Aggregation to aggregate smaller, adjacent class regions to a larger region. Aggregation is a useful post-classification cleanup process when the classification output includes many small regions.

You can also write a script to perform classification aggregation using the ClassificationAggregation task.

  1. From the Toolbox, select Classification > Post Classification > Classification Aggregation. The Classification Aggregation dialog appears.
  2. Select a classified image and perform any optional spatial subsetting, then click OK.
  3. Enter the Minimum Size in pixels. Regions with a size of this value or smaller are aggregated to an adjacent, larger region.
  4. In the Aggregate Unclassified Pixels field, select whether to treat unclassified pixels as a class that other pixels can be aggregated into.
  5. Enter an Output Raster filename and directory.
  6. 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.

  7. 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.

  8. To reuse these task settings in future ENVI sessions, save them to a file. Click the down arrow next to the OK button and 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 stored your settings.

  9. To run the process in the background, click the down arrow next to the OK button and select Run Task in the Background. If an ENVI Server has been set up on the network, the Run Task on remote ENVI Server name is also available. The ENVI Server Job Console will show the progress of the job and will provide a link to display the result when processing is complete. See ENVI Servers for more information.

  10. Click OK.