CImCombine:SetNormStat
The SetNormStat method specifies the statistic used to determine the correction needed to normalize each image to the reference image. The statistics are similar to those used by the combining methods, except that the normalization statistic produces a single number applied to the entire image.
CImCombine:SetNormStat( stat, par1, par2, par3 ) |
stat specifies the statistic (see table in the Remarks section, below).
par1, par2, and par3 are optional parameters used by the various statistics.
The normalization statistic may be any of the methods listed in the table below. Parameters are also listed. If not specified, as an argument, all parameters adopt reasonable values. For example, the default values for sigma clipping parameters are 2.5, the default values for alpha clipping parameters are 1, and the default values for rank clipping parameters are 2.5 (percentile). Both power parameters default to 0.5.
Normalization Methods
Stat Name |
Description of the Statistic |
Par1 |
Par2 |
Par3 |
Alpha Clip |
Mean, excluding alpha high values and alpha low values. See AlphaClip |
nHigh |
nLow |
|
Contra Mean |
The contra-harmonic mean of pixel values. See ContraMean |
power |
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Geometric Mean |
The geometric mean of pixel values. See GeometricMean |
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Max |
Maximum pixel value |
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MaxClip |
Mean, excluding maximum pixel value. See MaxClip |
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Mean |
Unweighted mean value |
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Median |
Median value |
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Min |
Minimum pixel value |
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MmClip |
Mean, excluding maximum and minimum pixel values. See MmClip |
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|
Mtm Sigma Clip |
Mean, excluding values outside upper and lower sigma limits relative to the median. See MtmSigmaClip |
nHigh |
nLow |
nIter |
Rank |
Rank percentile value. See Rank |
percentile |
|
|
Rank Clip |
Mean after clipping pixel values above and below rank percentiles. See RankClip |
pHigh |
pLow |
|
Sigma Clip |
Mean, excluding values outside upper and lower sigma limits. See SigmaClip |
nHigh |
nLow |
nIter |
Yp Mean |
The Yp Power weighted mean of pixel values. See YpMean |
power |
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The following script uses SetNormStat to specify the normalization statistic as sigma clipping with 2.5 sigma rejection above and 5 sigma rejection below the mean:
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-- create a CImCombine object |
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-- central 10% of the image |
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-- specify CImage and CRect to measure |
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-- use the median as the statistic |
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-- scale to normalize the image set |
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-- combine image set and return new image |
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-- show the new image |
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-- when done with S, remove it from memory |
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