This is a utility routine to perform basic gray-level pixel transformations of images. I think of it as BYTSCL on steroids. It is similar to IMADJUST in _Digital Image Processing with MATLAB_ by Gonzales, Wood, and Eddins. It performs a log scaling of the image array.
Image Processing
A byte scaled image is returned.
image: in, required The image to be scaled. Written for 2D images, but arrays of any size are treated alike.
gamma: in, optional, type=float, default=1.0 The exponent in a power-law transformation (image^gamma). A gamma value of 1 results in a linear distribution of values between OMIN and OMAX. Gamma values less than 1 map darker image values into a wider range of output values, and Gamma values greater than 1 maps lighter image values into a wider range of output values. The gamma value is constrained to be greater than 1.0e-6. 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.
cgLoadCT, 0 ; Gray-scale colors. image = cgDemoData(11) ; Load image. TVImage, cgGmaScl(image, Min=30, Max=100) ; Similar to BytScl. TVImage, cgGmaScl(image, /Negative) ; Produce negative image. power = Shift(ALog(Abs(FFT(image,-1))), 124, 124) ; Create power spectrum. TVImage, cgGmaScl(power, Gamma=2.5) ; View power specturm with gamma correction. TVImage, cgGmaScl(power, Gamma=2.5, /Negative) ; Reverse power spectrum.
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
Change History:: Written by: David W. Fanning, 17 February 2006. Fixed a problem with output scaling. 1 July 2009. DWF (with input from Bo Milvang-Jensen). Now setting NAN keyword on all MIN and MAX functions. 2 Dec 2011. DWF. Renamed cgGmaScl from GmaScl. 27 March 2015. DWF.
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