pyextal.acom.detect
===================

.. py:module:: pyextal.acom.detect

.. autoapi-nested-parse::

   Bragg peak detection in an averaged diffraction pattern.



Functions
---------

.. autoapisummary::

   pyextal.acom.detect.detect_peaks
   pyextal.acom.detect.direct_beam


Module Contents
---------------

.. py:function:: detect_peaks(image, min_distance=4, threshold_rel=0.02, num_peaks=200, refine=True, crop=5)

   Finds Bragg peaks and refines them to sub-pixel positions.

   :param image: 2D averaged diffraction pattern.
   :type image: np.ndarray
   :param min_distance: Smallest separation between peaks, in
                        pixels. Defaults to 4.
   :type min_distance: int, optional
   :param threshold_rel: Peak height floor as a fraction of the
                         brightest pixel. Defaults to 0.02.
   :type threshold_rel: float, optional
   :param num_peaks: Most peaks to return. Defaults to 200.
   :type num_peaks: int, optional
   :param refine: Fit a 2D Gaussian to each peak for sub-pixel
                  accuracy. Defaults to True.
   :type refine: bool, optional
   :param crop: Half-width of the patch fitted per peak. Defaults to 5.
   :type crop: int, optional

   :returns: ``(positions, intensities)`` -- (n, 2)
             float pixel coordinates in (x, y) = (row, col) detector convention, and
             the peak height at each.
   :rtype: tuple[np.ndarray, np.ndarray]


.. py:function:: direct_beam(positions, intensities, hint=None, search=8.0)

   Picks the direct beam from a set of detected peaks.

   :param positions: (n, 2) peak positions.
   :type positions: np.ndarray
   :param intensities: (n,) peak heights.
   :type intensities: np.ndarray
   :param hint: Approximate position; the nearest
                peak within `search` pixels is taken. The brightest peak is used
                when None.
   :type hint: tuple[float, float], optional
   :param search: Radius around `hint`, in pixels. Defaults to 8.
   :type search: float, optional

   :returns: Index into `positions`, and the position itself.
   :rtype: tuple[int, np.ndarray]

   :raises ValueError: If no peak was found, or none lies near `hint`.