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CImCombine:KwdWeightedMean
The KwdWeightedMean method combines the images by a weighted mean using the value of a header keyword as the weight.
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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.
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.
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:
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C = CImCombine:new() |
-- create a CImCombine object |
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R = CRect:new(10,50,10,50) |
-- central 10% of the image |
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C:SetRelRect( R ) |
-- specify CImage and CRect to measure |
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C:SetNormStat("median") |
-- use the MmClip as the normalization statistic |
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C:SetNormMethod("scale") |
-- scale to normalize the image set |
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I = C:KwdWeightedMean(S,"Exptime") |
-- combine image set and return new image |
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I:Display() |
-- show the new image |
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C:delete() |
-- when done with S, remove it from memory |