Hit finders

Number of pixels above threshold

Total intensity above threshold

Peak finders

Two threshold algorithm

peak_finder_v1

Flood filling algorithm

peak_finder_v2

Local maximums search algorithm

peak_finder_v3

• 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)

Demonstration for local maximum map

Test for 100x100 image with random normal distribution of intensities

Example of the map of local maximums found for rank from 1 to 5:

color coding of pixels:

• blue=0 - not a local maximum
• green=1 - local maximum in row
• yellow=1+2 - local maximum in row and column
• red=1+2+4 - local maximum in rectangular region of radius=rank.

Table for rank, associated 2-d region size, fraction of pixels recognized as local maximums for rank, and time consumption for this algorithm.

References

• ImgAlgos.PyAlgos - code example in Sphinx documentation
• Peak Finding - short announcement about peak finders
• Hit and Peak Finders - examples in Chris' tutorial
• Peak Finding Module - (depricated) psana module, it demonstaration examples and results
• Psana Module Catalog - (depricated) peak finding  psana modules
• Psana Module Examples - (depricated) peak finding examples in psana modules
• GUI for tuning peak finding - Chun's page in development