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This algorithm was motivated by users of amo42112:
1. Select the pixels in the window xmin, xmax, ymin, ymax
with amplitudes above the threshold_low.
2. Smear image for selected pixels, using 2-d matrix of weights over pixels
from -smear_radius to +smear_radius around each smeared pixel amplitude.
The matrix of weights is defined by the 2-d Gaussian function of width sigma.
3. Find peaks as pixels with absolute-maximal amplitude above the threshold_high in the center of the matrix -peak_radius to +peak_radius.
4. Put the vector or ndarray of found peaks in the event with key peaksKey or peaks_nda respectively. Each entry of this vector has an object of the struct Peak, containing x, y positions, peak pixel amplitude, the total amplitude in the matrix, defined by the peak_radius, and the number of pixels in the matrix above threshold_low:
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parameter | default value | description |
|---|---|---|
| "DetInfo()" | source of data |
|
| key for input image data |
| "peaks" | key for output list of peaks as std::vector<Peak> (if empty - do not save) |
peaks_nda | key for output list of peaks ndarray<float,2> with shape=[npeaks,5]. Is empty by default (if empty - do not save) | |
| 10 | low threshold on pixel amplitude |
| 100 | high threshold on pixel amplitude |
| 1.5 | width of the Gaussian for smearing; =0-no smearing |
| 3 | radius in pixel for smearing - radial size of matrix of weights |
| 3 | radius in pixel for peak finding - radial size of the region to search for local maximum |
| 0 | minimal column number |
| 100000 | maximal column number |
| 0 | minimal row number |
| 100000 | maximal row number |
| 0 | event number to save images and print info for test purpose |
| true | On/Off algorithm |
| 0 | module verbosity:
|
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- This algorithm consumes ~15 ms/event on psana0101 for full Opal1000 (1024x1024) camera image.
- Smearing algorithm use a "safety margin" which is currently set to 10 pixels (offset from each boarder of the full image size).
- Since V00-03-58 saves table of peaks as ndarray<float,2> with shape=[npeaks,5] if key
peaks_ndais non-empty.
See also Example for Module ImgAlgos::ImgPeakFinder.
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