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*Subject*: Re: Function BYTSCL*From*: "Liam E. Gumley" <Liam.Gumley(at)ssec.wisc.edu>*Date*: Tue, 10 Apr 2001 09:44:22 -0500*Newsgroups*: comp.lang.idl-pvwave*Organization*: Space Science and Engineering Center, UW-Madison*References*: <3AD2C46C.5892EA9F@student.uni-magdeburg.de>*Xref*: news.doit.wisc.edu comp.lang.idl-pvwave:24487

Steffen Kernchen wrote: > what function(s) can I use instead of BYTSCL? > I have an array and I want to transform it to get a better contrast. > But I should NOT use BYTSCL.... :( It sounds like you want to do something other than selecting the minimum and maximum array values for the scaling range used in BYTSCL. How about trying histogram clipping? (1) Compute a histogram for the image at N (say N=100) intervals between the minimum and maximum array values. (2) From the low end of the histogram, find the histogram bin where X percent (say X=2) of the total number of array elements (pixels) lie to the *left* of the current bin. The data value for this bin becomes the minimum of the scaling range. Perform a similar search from the high end of the histogram to obtain the maximum of the scaling range. (3) Now use BYTSCL with the derived scaling range to create a contrast enhanced image. Other functions that will be useful in this exercise are HISTOGRAM and TOTAL. Cheers, Liam. http://cimss.ssec.wisc.edu/~gumley

**References**:**Function BYTSCL***From:*Steffen Kernchen

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