# coyote: CGLOGSCL

- coyote/Image Processing
- [Source code]

Description

      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.