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CGLOGSCL

CGLOGSCL
  This is a utility routine to perform a logarithmic transformation
  on an image. The shape of the transformation is similar to the gamma
  curve (see cgGmaScl), except that the shape of the gamma curve is
  variable, while the log curve is fixed. The function is used to improve
  contrast in images. The equation being implemented before scaling between
  OMIN and OMAX is as follows::
 
    output = constant * Log(1 + double(input))

Categories


    Image Processing

Returns


    A byte scaled image is returned.

Params


    image: in, required
      The image to be scaled. Written for 2D images, but arrays of any size are treated alike.

Keywords


    constant: in, optional, type=float, default=1.0
        A contant value by which the log result is multiplied.
    max: in, optional
          Any value in the input image greater than this value is set to this value
          before scaling.
         
    min: in, optional
          Any value in the input image less than this value is set to this value
          before scaling.
    negative, in, optional, type=boolean, default=0
          If set, the "negative" of the result is returned.
    omax: in, optional, type=byte, default=255
          The output image is scaled between OMIN and OMAX.
    omin: in, optional, type=byte, default=0
          The output image is scaled between OMIN and OMAX.

Examples


    Examples of compression stretching::
      cgLoadCT, 0 ; Gray-scale colors.
      image = cgDemoData(22) ; Load image.
      cgImage, image ; No contrast.
      cgImage, cgLogScl(image) ; Improved contrast.

Author


      FANNING SOFTWARE CONSULTING::
          David W. Fanning
          1645 Sheely Drive
          Fort Collins, CO 80526 USA
          Phone: 970-221-0438
          E-mail: david@idlcoyote.com
          Coyote's Guide to IDL Programming: http://www.idlcoyote.com

History


    Change History::
      Written by: David W. Fanning, 27 March 2015. DWF.

Copyright


    Copyright (c) 2015, Fanning Software Consulting, Inc.



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