rsstretch bf

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Contents: Description, Arguments, Usage, Examples, Images, Sub-Functions, Related Functions, Source

Description

This version of running sigma stretch uses boxfilter and its verbose options to produce a unique standard devation for every pixel in the data. One disadvantage of this running stretch is that it uses boxfiter and can't handle large arrays based on the properties of boxfilter. If a large array needs to be stretchted rsstretch is much more memory efficient. The stretch is esentially "running" or changing over the whole data set. This process helps eliminate image wide variations and maximizes local variation producing a "harder" stretch. This is evident when looking at the sample images below.

Changing the x and y sizes will ultimately determine how local or regional features affect the stretch.

Arguments and Return Values

Arguments: Accepts any numeric array

Return Value: A stretched byte array

Usage

Syntax: rsstretch_bf(data = VAL [, ignore = FLOAT] [, size = INT] [, variance = FLOAT])

'data' - Any numeric array

'ignore' - Ignore value of the black space. Default of -32768.

'size' - Any integer for the size of the area used to calculate the standard devatin. Default of 1000.

'variance' - variance of the stretch. Default of 40.

Examples

dv> a
829x3622x1 array of float, bsq format [12,010,552 bytes]

The two methods below are equivalent and yeild the same results, but the second can be used for more memory efficient processing.

dv> b = rsstretch_bf(a,size=500,ignore=-32768)
829x3622x1 array of byte, bip format [3,002,638 bytes]

dv> b = rsstretch_bf(data=a,size=500,ignore-=32768)
829x3622x1 array of byte, bip format [3,002,638 bytes]

Images

The stretch of the left image is dominated by the canyon's huge difference in values (visible as contrast) and consequently the plains appear washed out. The stretch on the right is more consistent throughout normalizing the plains above the canyon to have a similar stretch as the canyon itself.