CImCombine:AlphaClip

The AlphaClip method merges the pixel values using alpha-clipping to remove some specified number of high and low outlying values at each location.

Syntax

CImage = CImCombine:AlphaClip( CImageSet, nHigh, nLow )

CImageSet contains the collection of images to be combined.
nHigh is the number of highest pixel values to exclude.
nLow is the number of lowest pixel values to exclude.
CImage is a new image created by this method.
On success, this method returns a new CImage.
On failure, this method returns nil.

Remarks

Each pixel in the output image is the mean value of all images except the nHigh highest values and the nLow lowest values at each location. In order for the AlphaClip method to work properly, normalization must be done as part of the combining.

Example

Suppose a CImageSet named S exists. The following script fragment combines the images by the AlphaClip method by excluding the 2 highest and 1 lowest values from the sample at each location. The images are normalized by the Median statistic computed inside the central 10% of the image:

C = CImCombine:new()	-- create a CImCombine object
R = CRect:new(10,50,10,50)	-- central 10% of the image
C:SetRelRect( R )	-- specify CImage and CRect to measure
C:SetNormStat("median")	-- use the AlphaClip as the normalization statistic
C:SetNormMethod("scale")	-- scale to normalize the image set
I = C:AlphaClip(S,2,1)	-- combine the image set and return a new image
I:Display()	-- show the new image
C:delete()	-- when done with S, remove it from memory