Use Clump Classes to clump adjacent similarly classified areas together using morphological operators. Classification images often suffer from a lack of spatial coherency (speckle or holes in classified areas). Low pass filtering could be used to smooth these images, but the class information would be contaminated by adjacent class codes. Clumping classes solves this problem. The selected classes are clumped together by first performing a dilate operation then an erode operation on the classification image using a kernel of the size specified in the parameters dialog.

You can also write a script to perform classification clumping using the ClassificationClumping task.

  1. From the Toolbox, select Classification > Post Classification > Clump Classes. The Classification Input File dialog appears.
  2. Select an input file, perform any optional spatial subsetting, and then click OK to display the Classification Clumping dialog. Clumping can only be performed on classification images, identified by a file type of "ENVI Classification" in the image header file.
  3. Specify a Dilate Kernel Value. This field represents the structuring element used to expand shapes contained in the input image. An array size of 3x3 and element values of 1 are used unless otherwise specified.
  4. Specify an Erode Kernel Value. This field represents the structuring element used to reduce shapes contained in the input image. An array size of 3x3 and element values of 1 are used unless otherwise specified.
  5. Use the Class Order list to identify which classes will have clumping applied. Classes may be added, removed or reordered. If no changes are made, all classes have clumping applied and are processed from first to last.
  6. Use Output Raster to specify an output location and filename.

  7. To reuse these task settings in future ENVI sessions, save them to a file. Click the down arrow and select Save Parameter Values, then specify the location 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.

  8. To run the process in the background, click the down arrow 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.

  9. Click OK.