CImCombine:KwdWeightedMean

The KwdWeightedMean method combines the images by a weighted mean using the value of a header keyword as the weight.

Syntax

CImage = CImCombine:KwdWeightedMean( CImageSet, sKeyword )

CImageSet contains the collection of images to be combined.
sKeyword is the name of the header keyword whose value is used as a weight.
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 using a normalized keyword value as the weight. For example, this method can be used to combine images in an "optimal" sense using the exposure time as a weighting factor. The keyword values are collected and normalized to unit weight.

Example

Suppose a CImageSet named S exists. The following script fragment combines the images by the KwdWeightedMean method using the exposure time keyword as a weight. 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 MmClip as the normalization statistic
C:SetNormMethod("scale")	-- scale to normalize the image set
I = C:KwdWeightedMean(S,"Exptime")	-- combine image set and return new image
I:Display()	-- show the new image
C:delete()	-- when done with S, remove it from memory