OpenPIV tutorial of all test cases¶

In [1]:

from openpiv import tools, pyprocess, scaling, validation, filters
import numpy as np
import glob
%matplotlib inline

In [2]:

%load_ext watermark
%watermark -v -m -p numpy,openpiv -g -b

CPython 3.8.5
IPython 7.19.0

numpy 1.19.4
openpiv 0.23.1a0

compiler   : GCC 7.3.0
system     : Linux
release    : 5.4.0-54-generic
machine    : x86_64
processor  : x86_64
CPU cores  : 8
interpreter: 64bit
Git hash   : 6edda3f747a61489b040b4d59a7a6d0442e8e341
Git branch : sig2noise_validation

In [3]:

# set of typical parameters
window_size = 32  # pixels 32 x 32 pixels interrogation window, in frame A.
overlap = 16  # overlap is 8 pixels, i.e. 25% of the window
search_size = 40  # pixels 64 x 64 in frame B, avoids some peak locking for 
                  # large displacements

In [4]:

def openpiv_default_run(im1,im2):
    """ default settings for OpenPIV analysis using
    extended_search_area_piv algorithm for two images
    
    Inputs:
        im1,im2 : str,str = path of two image
    """
    frame_a  = tools.imread(im1)
    frame_b  = tools.imread(im2)

    u, v, sig2noise = pyprocess.extended_search_area_piv(frame_a.astype(np.int32), 
                                                       frame_b.astype(np.int32), 
                                                       window_size=window_size, 
                                                       overlap=overlap, 
                                                       dt=1, 
                                                       search_area_size=search_size, 
                                                       sig2noise_method='peak2mean',
                                                       correlation_method='circular',
                                                       normalized_correlation=True)
    x, y = pyprocess.get_coordinates(frame_a.shape, 
                                     search_size, 
                                     overlap)
    # 5% lowest range
    u, v, mask = validation.sig2noise_val(u, v, 
                                          sig2noise, 
                                          threshold = np.percentile(sig2noise,2.5))
    u, v = filters.replace_outliers( u, v, method='localmean', 
                                    max_iter=3, kernel_size=3)
    x, y, u, v = scaling.uniform(x, y, u, v, scaling_factor = 1. )
    tools.save(x, y, u, v, sig2noise, mask, list_of_images[0]+'.txt' )
    fig,ax = tools.display_vector_field(list_of_images[0]+'.txt', 
                                        on_img=True,image_name=list_of_images[0],
                                        scaling_factor=1.,
                                        ax=None)

In [5]:

alist_filter = ['jpg','bmp','png','tif','tiff']


# all test cases in /openpiv/examples/
list_of_tests = glob.glob('../test*')
list_of_tests.sort()

list_of_images = []
for test in list_of_tests:
    
    list_of_files = glob.glob(test+'/*.*')
    list_of_files.sort()
    list_of_images = [f for f in list_of_files if f[-3:] in alist_filter]
    if len(list_of_images) > 0:
        openpiv_default_run(list_of_images[0],list_of_images[1])

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