440 ):
441 r"""Deblend a parent ``Footprint`` in a ``MaskedImageF``.
442
443 Deblending assumes that ``footprint`` has multiple peaks, as it will still create a
444 `PerFootprint` object with a list of peaks even if there is only one peak in the list.
445 It is recommended to first check that ``footprint`` has more than one peak, similar to the
446 execution of `lsst.meas.deblender.deblend.SourceDeblendTask`.
447
448 .. note::
449 This is the API for the old deblender, however the function builds the plugins necessary
450 to use the new deblender to perform identically to the old deblender.
451 To test out newer functionality use ``newDeblend`` instead.
452
453 Deblending involves several mandatory and optional steps:
454
455 # Optional: If ``fitPsfs`` is True, find all peaks that are well-fit by a PSF + background model
456
457 * Peaks that pass the cuts have their footprints modified to the PSF + background model
458 and their ``deblendedAsPsf`` property set to ``True``.
459 * Relevant parameters: ``psfChisqCut1``, ``psfChisqCut2``, ``psfChisqCut2b``,
460 ``tinyFootprintSize``.
461 * See the parameter descriptions for more.
462
463 # Build a symmetric template for each peak not well-fit by the PSF model
464
465 * Given ``maskedImageF``, ``footprint``, and a ``DeblendedPeak``, creates a symmetric
466 template (``templateImage`` and ``templateFootprint``) around the peak
467 for all peaks not flagged as ``skip`` or ``deblendedAsPsf``.
468 * If ``patchEdges=True`` and if ``footprint`` touches pixels with the
469 ``EDGE`` bit set, then ``footprint`` is grown to include spans whose
470 symmetric mirror is outside of the image.
471 * Relevant parameters: ``sigma1`` and ``patchEdges``.
472
473 # Optional: If ``rampFluxAtEdge`` is True, adjust flux on the edges of the template footprints
474
475 * Using the PSF, a peak ``Footprint`` with pixels on the edge of of ``footprint``
476 is grown by the psffwhm*1.5 and filled in with zeros.
477 * The result is a new symmetric footprint template for the peaks near the edge.
478 * Relevant parameter: ``patchEdges``.
479
480 # Optionally (``medianSmoothTemplate=True``) filter the template images
481
482 * Apply a median smoothing filter to all of the template images.
483 * Relevant parameters: ``medianFilterHalfSize``
484
485 # Optional: If ``monotonicTemplate`` is True, make the templates monotonic.
486
487 * The pixels in the templates are modified such that pixels
488 further from the peak will have values smaller than those closer to the peak.
489
490 # Optional: If ``clipFootprintToNonzero`` is True, clip non-zero spans in the template footprints
491
492 * Peak ``Footprint``\ s are clipped to the region in the image containing non-zero values
493 by dropping spans that are completely zero and moving endpoints to non-zero pixels
494 (but does not split spans that have internal zeros).
495
496 # Optional: If ``weightTemplates`` is True, weight the templates to best fit the observed image
497
498 * Re-weight the templates so that their linear combination
499 best represents the observed ``maskedImage``
500
501 # Optional: If ``removeDegenerateTempaltes`` is True, reconstruct shredded galaxies
502
503 * If galaxies have substructure, such as face-on spirals, the process of identifying peaks can
504 "shred" the galaxy into many pieces. The templates of shredded galaxies are typically quite
505 similar because they represent the same galaxy, so we try to identify these "degenerate" peaks
506 by looking at the inner product (in pixel space) of pairs of templates.
507 * If they are nearly parallel, we only keep one of the peaks and reject the other.
508 * If only one of the peaks is a PSF template, the other template is used,
509 otherwise the one with the maximum template value is kept.
510 * Relevant parameters: ``maxTempDotProduct``
511
512 # Apportion flux to all of the peak templates
513
514 * Divide the ``maskedImage`` flux amongst all of the templates based on the fraction of
515 flux assigned to each ``tempalteFootprint``.
516 * Leftover "stray flux" is assigned to peaks based on the other parameters.
517 * Relevant parameters: ``clipStrayFluxFraction``, ``strayFluxAssignment``,
518 ``strayFluxToPointSources``, ``assignStrayFlux``
519
520 Parameters
521 ----------
522 footprint: `afw.detection.Footprint`
523 Parent footprint to deblend
524 maskedImage: `afw.image.MaskedImageF`
525 Masked image containing the ``footprint``
526 psf: `afw.detection.Psf`
527 Psf of the ``maskedImage``
528 psffwhm: `float`
529 FWHM of the ``maskedImage``\'s ``psf``
530 psfChisqCut*: `float`, optional
531 If ``fitPsfs==True``, all of the peaks are fit to the image PSF.
532 ``psfChisqCut1`` is the maximum chi-squared-per-degree-of-freedom allowed for a peak to
533 be considered a PSF match without recentering.
534 A fit is also made that includes terms to recenter the PSF.
535 ``psfChisqCut2`` is the same as ``psfChisqCut1`` except it determines the restriction on the
536 fit that includes recentering terms.
537 If the peak is a match for a re-centered PSF, the PSF is repositioned at the new center and
538 the peak footprint is fit again, this time to the new PSF.
539 If the resulting chi-squared-per-degree-of-freedom is less than ``psfChisqCut2b`` then it
540 passes the re-centering algorithm.
541 If the peak passes both the re-centered and fixed position cuts, the better of the two is accepted,
542 but parameters for all three psf fits are stored in the ``DeblendedPeak``.
543 The default for ``psfChisqCut1``, ``psfChisqCut2``, and ``psfChisqCut2b`` is ``1.5``.
544 fitPsfs: `bool`, optional
545 If True then all of the peaks will be compared to the image PSF to
546 distinguish stars from galaxies.
547 medianSmoothTemplate: ``bool``, optional
548 If ``medianSmoothTemplate==True`` it a median smoothing filter is applied to the ``maskedImage``.
549 The default is ``True``.
550 medianFilterHalfSize: `int`, optional
551 Half the box size of the median filter, ie a ``medianFilterHalfSize`` of 50 means that
552 each output pixel will be the median of the pixels in a 101 x 101-pixel box in the input image.
553 This parameter is only used when ``medianSmoothTemplate==True``, otherwise it is ignored.
554 The default value is 2.
555 monotonicTempalte: `bool`, optional
556 If True then make the template monotonic.
557 The default is True.
558 weightTemplates: `bool`, optional
559 If True, re-weight the templates so that their linear combination best represents
560 the observed ``maskedImage``.
561 The default is False.
562 log:`lsst.log.Logger` or `lsst.utils.logging.LsstLogAdapter`, optional
563 LSST logger for logging purposes.
564 If `None`, a default logger will be created named after this module.
565 verbose: `bool`, optional
566 Whether or not to show a more verbose output. This option only affects
567 the logger creeated internally and will not change the reporting level
568 of an externally-supplied logger.
569 The default is ``False``.
570 sigma1: `float`, optional
571 Average noise level in ``maskedImage``.
572 The default is ``None``, which estimates the noise from the median value of ``maskedImage``.
573 maxNumberOfPeaks: `int`, optional
574 If nonzero, the maximum number of peaks to deblend.
575 If the total number of peaks is greater than ``maxNumberOfPeaks``,
576 then only the first ``maxNumberOfPeaks`` sources are deblended.
577 The default is 0, which deblends all of the peaks.
578 assignStrayFlux: `bool`, optional
579 If True then flux in the parent footprint that is not covered by any of the
580 template footprints is assigned to templates based on their 1/(1+r^2) distance.
581 How the flux is apportioned is determined by ``strayFluxAssignment``.
582 The default is True.
583 strayFluxToPointSources: `string`
584 Determines how stray flux is apportioned to point sources
585
586 * ``never``: never apportion stray flux to point sources
587 * ``necessary`` (default): point sources are included only if there are no extended sources nearby
588 * ``always``: point sources are always included in the 1/(1+r^2) splitting
589
590 strayFluxAssignment: `string`, optional
591 Determines how stray flux is apportioned.
592
593 * ``trim``: Trim stray flux and do not include in any footprints
594 * ``r-to-peak`` (default): Stray flux is assigned based on (1/(1+r^2) from the peaks
595 * ``r-to-footprint``: Stray flux is distributed to the footprints based on 1/(1+r^2) of the
596 minimum distance from the stray flux to footprint
597 * ``nearest-footprint``: Stray flux is assigned to the footprint with lowest L-1 (Manhattan)
598 distance to the stray flux
599
600 rampFluxAtEdge: `bool`, optional
601 If True then extend footprints with excessive flux on the edges as described above.
602 The default is False.
603 patchEdges: `bool`, optional
604 If True and if the footprint touches pixels with the ``EDGE`` bit set,
605 then grow the footprint to include all symmetric templates.
606 The default is ``False``.
607 tinyFootprintSize: `float`, optional
608 The PSF model is shrunk to the size that contains the original footprint.
609 If the bbox of the clipped PSF model for a peak is smaller than ``max(tinyFootprintSize,2)``
610 then ``tinyFootprint`` for the peak is set to ``True`` and the peak is not fit.
611 The default is 2.
612 getTemplateSum: `bool`, optional
613 As part of the flux calculation, the sum of the templates is calculated.
614 If ``getTemplateSum==True`` then the sum of the templates is stored in the result (a `PerFootprint`).
615 The default is False.
616 clipStrayFluxFraction: `float`, optional
617 Minimum stray-flux portion.
618 Any stray-flux portion less than ``clipStrayFluxFraction`` is clipped to zero.
619 The default is 0.001.
620 clipFootprintToNonzero: `bool`, optional
621 If True then clip non-zero spans in the template footprints. See above for more.
622 The default is True.
623 removeDegenerateTemplates: `bool`, optional
624 If True then we try to identify "degenerate" peaks by looking at the inner product
625 (in pixel space) of pairs of templates.
626 The default is False.
627 maxTempDotProduct: `float`, optional
628 All dot products between templates greater than ``maxTempDotProduct`` will result in one
629 of the templates removed. This parameter is only used when ``removeDegenerateTempaltes==True``.
630 The default is 0.5.
631
632 Returns
633 -------
634 res: `PerFootprint`
635 Deblender result that contains a list of ``DeblendedPeak``\ s for each peak and (optionally)
636 the template sum.
637 """
638 avgNoise = sigma1
639
640 debPlugins = []
641
642
643 if fitPsfs:
644 debPlugins.append(plugins.DeblenderPlugin(plugins.fitPsfs,
645 psfChisqCut1=psfChisqCut1,
646 psfChisqCut2=psfChisqCut2,
647 psfChisqCut2b=psfChisqCut2b,
648 tinyFootprintSize=tinyFootprintSize))
649 debPlugins.append(plugins.DeblenderPlugin(plugins.buildSymmetricTemplates, patchEdges=patchEdges))
650 if rampFluxAtEdge:
651 debPlugins.append(plugins.DeblenderPlugin(plugins.rampFluxAtEdge, patchEdges=patchEdges))
652 if medianSmoothTemplate:
653 debPlugins.append(plugins.DeblenderPlugin(plugins.medianSmoothTemplates,
654 medianFilterHalfsize=medianFilterHalfsize))
655 if monotonicTemplate:
656 debPlugins.append(plugins.DeblenderPlugin(plugins.makeTemplatesMonotonic))
657 if clipFootprintToNonzero:
658 debPlugins.append(plugins.DeblenderPlugin(plugins.clipFootprintsToNonzero))
659 if weightTemplates:
660 debPlugins.append(plugins.DeblenderPlugin(plugins.weightTemplates))
661 if removeDegenerateTemplates:
662 if weightTemplates:
663 onReset = len(debPlugins)-1
664 else:
665 onReset = len(debPlugins)
666 debPlugins.append(plugins.DeblenderPlugin(plugins.reconstructTemplates,
667 onReset=onReset,
668 maxTempDotProd=maxTempDotProd))
669 debPlugins.append(plugins.DeblenderPlugin(plugins.apportionFlux,
670 clipStrayFluxFraction=clipStrayFluxFraction,
671 assignStrayFlux=assignStrayFlux,
672 strayFluxAssignment=strayFluxAssignment,
673 strayFluxToPointSources=strayFluxToPointSources,
674 getTemplateSum=getTemplateSum))
675
676 debResult = newDeblend(debPlugins, footprint, maskedImage, psf, psffwhm, log, verbose, avgNoise)
677
678 return debResult
679
680