sunkit_image.trace.occult2(image, nsm1, rmin, lmin, nstruc, ngap, qthresh1, qthresh2)[source]

Implements the Oriented Coronal CUrved Loop Tracing (OCCULT-2) algorithm for loop tracing in images.

  • image (numpy.ndarray) – Image in which loops are to be detected.

  • nsm1 (int) – Low pass filter boxcar smoothing constant.

  • rmin (int) – The minimum radius of curvature of the loop to be detected in pixels.

  • lmin (int) – The length of the smallest loop to be detected in pixels.

  • nstruc (int) – Maximum limit of traced structures.

  • ngap (int) – Number of pixels in the loop below the flux threshold.

  • qthresh1 (float) – The ratio of image base flux and median flux. All the pixels in the image below qthresh1 * median intensity value are made to zero before tracing the loops.

  • qthresh2 (float) – The factor which determines noise in the image. All the intensity values between qthresh2 * median are considered to be noise. The median for noise is chosen after the base level is fixed.


list – A list of all loop where each element is itself a list of points containing x and y coordinates for each point.


  • Markus J. Aschwanden, Bart De Pontieu, Eugene A. Katrukha. Optimization of Curvi-Linear Tracing Applied to Solar Physics and Biophysics. Entropy, vol. 15, issue 8, pp. 3007-3030 https://doi.org/10.3390/e15083007