openpiv_cxx.windef.first_pass

openpiv_cxx.windef.first_pass(frame_a, frame_b, window_size=32, overlap=16, correlation_method='circular')

Zero order PIV

First pass of the PIV evaluation. This function does the PIV evaluation of the first pass. It returns the coordinates of the interrogation window centres, the displacment u and v for each interrogation window as well as the mask which indicates wether the displacement vector was interpolated or not.

Parameters:

  • frame_a (ndarray) – A two dimensional array of integers containing grey levels of the first frame.

  • frame_b (ndarray) – A two dimensional array of integers containing grey levels of the second frame.

  • window_size (int) – The size of the interrogation window.

  • overlap (int) – The overlap of the interrogation window, typically it is window_size/2.

Returns:

  • x, y (ndarray) – Array containg the x coordinates of the interrogation window centres.

  • u, v (ndarray) – Array containing the u/v displacement for every interrogation window.

  • s2n (ndarray) – Array consisting of signal to noise ratio values.