orca.transform.image_sub
========================

.. py:module:: orca.transform.image_sub

.. autoapi-nested-parse::

   Image subtraction utilities for FITS images.

   Provides functions for subtracting pairs or lists of FITS images
   and computing image statistics within specified regions.

   Originally written by Marin Anderson.



Functions
---------

.. autoapisummary::

   orca.transform.image_sub.rot_ellipse
   orca.transform.image_sub.image_sub
   orca.transform.image_sub.getimrms


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

.. py:function:: rot_ellipse(x: numpy.ndarray, y: numpy.ndarray, x0: float, y0: float, sigmax: float, sigmay: float, theta: float) -> numpy.ndarray

   Compute the ellipse equation value for a rotated ellipse.

   Points where the return value <= 1 are inside the ellipse.

   :param x: X coordinates.
   :param y: Y coordinates.
   :param x0: Ellipse center X coordinate.
   :param y0: Ellipse center Y coordinate.
   :param sigmax: Semi-major axis in X direction.
   :param sigmay: Semi-minor axis in Y direction.
   :param theta: Rotation angle in radians.

   :returns: Array of ellipse equation values at each (x, y) point.


.. py:function:: image_sub(file1: Union[str, List[str]], file2: Union[str, List[str]], out_dir, out_prefix='diff_', ref_index: int = 0) -> str

   Image subtraction for single image for lists of images. When the input is a list, it co-adds first before
       subtracting. Subtraction is file2 - file1. Output file is based on the basename of file1 with a prefix.

   :param file1: Previous image or list of images to be co-added
   :param file2: Next image or list of images to be co-added.
   :param out_dir: Output directory
   :param out_prefix: Output file prefix.
   :param ref_index: If the input is a list, the index for the reference fits file from which the header for the output
                     is extracted.

   :returns: Output file path.


.. py:function:: getimrms(filepath: List[str], radius: int = 0)

   Compute RMS, median, and frequency for a list of FITS images.

   Calculates image statistics either from a central 1000x1000 pixel box
   or from a circular aperture of specified radius centered on the image.

   :param filepath: List of paths to FITS image files.
   :param radius: Aperture radius in pixels. If 0, uses central 1000x1000 box.

   :returns: Tuple of (rms_array, median_array, frequency_array, dateobs_array).