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 )

bullet.gif    CImageSet contains the collection of images to be combined.

bullet.gif    sKeyword is the name of the header keyword whose value is used as a weight.

bullet.gif    CImage is a new image created by this method.

bullet.gif    On success, this method returns a new CImage.

bullet.gif    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 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 = new_imcombine()

-- create a CImCombine object

R = new_rect(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

Related Topics

CImCombine class, CImageSet class, CImage class, CRect class


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