How to extract and apply LAS classification RGB values to a point cloud using the programming interface (API)

The following example code show how to access the classification values in a LAS file and create a new project file that will display the point cloud by the classification RGB values.  This example uses the default Computed Classification Values described in the ENVI Lidar help.  The values may vary depending on the LAS file version:

 

Computed Classification Value	Description
0	Not processed
1	Unclassified
2	Terrain
3	Near terrain
5	Trees
6	Buildings
14	Power line
15	Power pole

  

;----------------------------------------------------

PRO setRGBbyClassificationStoredInLAS

  COMPILE_OPT idl2

  e = e3de(/headless)

  ;lasFile has classification values already written to it
  lasFileName = 'classificationIn.las'

  ;create a project from the las file
  oLidar = e.openlidar(lasFileName)

  startIndex = 0
  blockSize = 500000
  allClass = MAKE_ARRAY(blockSize, /BYTE)

  allread = 0

  ;Loop through all points, setting the RGB value based on the stored
  ;classification values of the points
  WHILE (allread eq 0) DO BEGIN
    pointsInRange = oLidar.GetPointsInRange(startIndex, blockSize, $
      ALL_ATTRIBS=ALL_ATTRIBS, $
      COUNT=nPointsRead)

    ;inClass holds the Classifications for this iteration of the While loop
    inClass = *ALL_ATTRIBS.CLASSIFICATIONS
    IF (nPointsRead LT blocksize) THEN allread = 1

    ;allClass holds all of the Classifications in the file
    allClass = [allClass,inClass]

    ;uniqAllClass is an array containing one entry for each unique Classification
    uniqAllClass = allClass[UNIQ(allClass, SORT(allClass))]

    rgb = MAKE_ARRAY(3,nPointsRead, /BYTE)
    FOREACH i, uniqAllClass DO BEGIN
      CASE i OF
        ;Add all possible product types - powerpole, nearterrain… setting the rgb values to the corresponding classification color.
        ;Unprocessed
        0: BEGIN
          index = WHERE(inClass EQ 0)
          red=190
          green=190
          blue=190
          rgb[0,index] = red
          rgb[1,index] = green
          rgb[2,index] = blue
        END

        ;Unclassified
        1: BEGIN
          index = WHERE(inClass EQ 1)
          red=255
          green=255
          blue=255
          rgb[0,index] = red
          rgb[1,index] = green
          rgb[2,index] = blue
        END

        ;Terrain
        2: BEGIN
          index = WHERE(inClass EQ 2)
          red=255
          green=177
          blue=100
          rgb[0,index] = red
          rgb[1,index] = green
          rgb[2,index] = blue
        END

        ;Near Terrain
        3: BEGIN
          index = WHERE(inClass EQ 3)
          red=128
          green=255
          blue=0
          rgb[0,index] = red
          rgb[1,index] = green
          rgb[2,index] = blue
        END

        ;Trees
        5: BEGIN
          index = WHERE(inClass EQ 5)
          red=0
          green=147
          blue=0
          rgb[0,index] = red
          rgb[1,index] = green
          rgb[2,index] = blue
        END

        ;Buildings
        6: BEGIN
          index = WHERE(inClass EQ 6)
          red=217
          green=217
          blue=0
          rgb[0,index] = red
          rgb[1,index] = green
          rgb[2,index] = blue
        END

        ;Power lines
        14: BEGIN
          index = WHERE(inClass EQ 14)
          red=255
          green=100
          blue=255
          rgb[0,index] = red
          rgb[1,index] = green
          rgb[2,index] = blue
        END

        ;Power poles
        15: BEGIN
          index = WHERE(inClass EQ 15)
          red=160
          green=80
          blue=0
          rgb[0,index] = red
          rgb[1,index] = green
          rgb[2,index] = blue
        END
        ELSE: PRINT, 'Bad value'
      ENDCASE
    ENDFOREACH

    startIndex += nPointsRead
  ENDWHILE

  e.CLOSE
END

;--------------------------------

MM June 12, 2015