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two-threshold peak-finding algorithm in restricted region around pixel with maximal intensity. Two threshold allows to speed-up this algorithms. It is assumed that only pixels with intensity above thr_high are pretending to be peak candidate centers. Candidates are considered as a peak if their intensity is maximal in the (square) region of radius around them. Low threshold in the same region is used to account for contributing to peak pixels.

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txt_peak_finder_v1 txt_peak_finder_v1

peak_finder_v1

peaks = alg.peak_finder_v1(nda, thr_low=10, thr_high=150, radius=5, dr=0.05)

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• defines (square) region to search for local maximum with intensity above thr_high and contributing pixels with intensity above  thr_lo,
• is used as a r0 parameter to evaluate background and noise rms as explained in section below.

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define peaks for regions of connected pixels above threshold

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txt_peak_finder_

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v4 txt_peak_finder_

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v4

peak_finder_

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v4

peaks = alg.peak_finder_v2v4(nda, thr_low=10, thr_high=150, rank=2, r0=5, dr=0.05)

Two neighbor pixels are assumed connected if have common side. Pixels with intensity above threshold thr are considered only.

Local maximums search algorithm

define peaks in local maximums of specified rank (radius), for example rank=2 means 5x5 pixel region around central pixel.

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The same algorithm as  peak_finder_v1 , but parameter radius is split for two rank and r0 with the same meaning as in  peak_finder_v3 .

Flood filling algorithm

define peaks for regions of connected pixels above threshold

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txt_peak_finder_v2 txt_peak_finder_v2

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peak_finder_

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v2

peaks = alg.peak_finder_v3v2(nda, rankthr=210, r0=5, dr=0.05)

Two neighbor pixels are assumed connected if have common side. Pixels with intensity above threshold thr are considered only.

Local maximums search algorithm

define peaks in local maximums of specified rank (radius), for example rank=2 means 5x5 pixel region around central pixel.

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txt_peak_finder_v3 txt_peak_finder_v3

peak_finder_v3

peaks = alg.peak_finder_v3(nda, rank=2, r0=5, dr=0.05)

• makes makes a map of pixels with local maximums of requested rank for data ndarray and mask, pixel code in the map may have bits 0/1/2/4 standing for not-a-maximum / maximum-in-row / maximum-in-column / maximum-in-rectangular-region of radius=rank.
• for each pixel with local maximal intensity in the region defined by the rank radius counts a number of pixels with intensity above zero, total positive intensity, center of gravity coordinates and rms,
• using parameters r0(ex.=5.0), dr(ex.=0.05) evaluates background level, rms of noise, and S/N for the pixel with maximal intensity.
• makes list of peaks which pass selector with parameters set in set_peak_selection_pars, for example

alg.set_peak_selection_pars(npix_min=5, npix_max=500, amax_thr=0, atot_thr=1000, son_min=6)

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• example

peaks = alg.set_peak_finderselection_v4(nda, thr_low=10, thr_high=150, rank=2, r0=5, dr=0.05)pars(npix_min=5, npix_max=500, amax_thr=0, atot_thr=1000, son_min=6)

 The same algorithm as  peak_finder_v1 , but parameter radius is split for two rank and r0 with the same meaning as in previous algoriths.

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