Source Properties Table
The CImExtract:Extract method creates a table of source properties for the sources it detects and characterizes in an image. For each source, the CImExtract:GetSource method returns a table of source properties as described below.
The returned table can be either a numerically indexed table (array) or a keyed table using the property names. For example, if the table returned by GetSource is named obj, then the center X coordinate is given by either obj.nCenterX or obj[11]. The return type for the Source Properties table (indexed table or keyed table) is controlled by the bUseIndex flag in the call to GetSource. If bUseIndex is omitted or false, a keyed table is returned containing named properties. If bUseIndex=true, then an indexed table is returned. In the table below, the property index is listed under the heading Index. The property name is listed under the heading Name.
Note that some values naturally involve an integer type value, such as iIndex or iMinY. Values beginning with the letter "i" may be processed by your script as either a number or integer value.
Index |
Name |
Description |
1 |
nDetectThreshold |
The threshold number of sigmas above true background used for detecting the source. |
2 |
nBackground |
The threshold luminosity value used for detecting the source, a number for the . |
3 |
nBackgroundLocal |
The local background value near the source, calculated using dThreshold sigmas above the local true background. |
4 |
nArea |
The source area, in pixels. |
5 |
nTotalLum |
The total luminosity of the source relative to a pixel value of zero. |
6 |
nNetLum |
The net luminosity of the source above the background value, nBackground. |
7 |
nAvgLum |
The average luminosity of the source above the background value, nBackground. |
8 |
nLumStdDev |
The standard deviation in luminosity above the background value, nBackground. |
9 |
nMinVal |
The minimum pixel value in the source. |
10 |
nMaxVal |
The maximum pixel value in the source. |
11 |
nCenterX |
The luminosity weighted x-coordinate of the source. |
12 |
nCenterY |
The luminosity weighted y-coordinate of the source. |
13 |
nCenterWorldX |
The luminosity weighted world x-coordinate of the source. |
14 |
nCenterWorldY |
The luminosity weighted world y-coordinate of the source. |
15 |
nMag |
The astronomical magnitude of the source. |
16 |
nMagErr |
The empirical (measured) uncertainty in the astronomical magnitude of the source. |
17 |
nMagErrT |
The theoretical (calculated) uncertainty in the astronomical magnitude of the source. |
18 |
nNetCount |
The net count of the source above background. |
19 |
nSNR |
The signal to noise ratio of the source. |
20 |
nRadiusGyration |
The radius of gyration of the source. |
21 |
nMajorAxis |
The major axis length, a, of the source. |
22 |
nMinorAxis |
The minor axis length, b, of the source. |
23 |
nEllipticity |
The ellipticity of the source, in terms of 1-b/a. |
24 |
nAngle |
The angle of the major axis of the source, relative to the positive x-axis. |
25 |
nPeakiness |
The peakiness index of the source. |
26 |
nConcentrationIndex |
The concentration index of the source. |
27 |
nEffectiveDiameter |
The weighted diameter of the source. |
28 |
nSkewnessX |
The source skewness as a statistical measure of profile symmetry in the x-coordinate direction. |
29 |
nSkewnessY |
The source skewness as a statistical measure of profile symmetry in the y-coordinate direction. |
30 |
nKurtosis |
The source kurtosis as a statistical measure of flatness. |
31 |
nFwhm |
The FWHM of the source from the profile fit. |
32 |
nFwhmPeak |
The FWHM peak value from the profile fit. |
33 |
nFwhmBg |
The background level of the source from the profile fit. |
34 |
iIndex |
The numeric index of the detected source. Holes appear in the original sequence of indices when sources are merged and the secondary source is eliminated as a separate entity. This is an integer value. |
35 |
iMinX |
The minimum x-coordinate (column number) of the source above background. This is an integer value. |
36 |
iMaxX |
The maximum x-coordinate (column number) of the source above background. This is an integer value. |
37 |
iMinY |
The minimum y-coordinate (row number) of the source above background. This is an integer value. |
38 |
iMaxY |
The maximum y-coordinate (row number) of the source above background. This is an integer value. |
39 |
iXatMinY |
The x-coordinate (column number) at the minimum y-coordinate (row number) of the source above background. This is an integer value. |
40 |
iXatMaxY |
The x-coordinate (column number) at the maximum y-coordinate (row number) of the source above background. This is an integer value. |
41 |
iYatMinX |
The y-coordinate (row number) at the minimum x-coordinate (column number) of the source above background. This is an integer value. |
42 |
iYatMaxX |
The y-coordinate (row number) at the maximum x-coordinate (column number) of the source above background. This is an integer value. |
43 |
iXatMinLum |
The x-coordinate (column number) at the minimum luminosity of the source above background. This is an integer value. |
44 |
iXatMaxLum |
The x-coordinate (column number) at the maximum luminosity of the source above background. This is an integer value. |
45 |
iYatMinLum |
The y-coordinate (row number) at the minimum luminosity of the source above background. This is an integer value. |
46 |
iYatMaxLum |
The y-coordinate (row number) at the maximum luminosity of the source above background. This is an integer value. |
47 |
iFirstX |
The first x-coordinate (lowest column number) at the start of the source. This is an integer value. |
48 |
iFirstY |
The first y-coordinate (lowest row number) at the start of the source. This is an integer value. |
49 |
nDetectThreshold2 |
Currently unused. |
Suppose an image window exists on the Mira screen. The script below performs source extraction on an image from this window and then repeatedly uses GetSource to fetch the (x,y) coordinates from each source's Source Properties table.
Before calling Extract, the default configuration is updated using a ImExtractParams table. Note that your ImExtractParams table does not need to be named Params as shown here.
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-- attach an image window |
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-- leave script if no image window |
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-- get the top-most or only image |
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-- leave script if no image |
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-- create a CImExtract object |
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-- setup an ImExtractParams table |
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-- use a comma after each "name=value" pair |
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-- threshold value = 45 |
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-- detect pixels >= threshold |
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-- set new configuration properties |
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-- extract sources from image I |
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-- report the number of sources extracted: |
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-- list the x,y coordinates for all sources: |
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-- fetch the properties of source i |
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CImExtract class, Count, Extract, GetSource
Mira Pro x64 Script User's Guide, Copyright Ⓒ 2023 Mirametrics,
Inc. All Rights Reserved.