import numpy as np
import matplotlib.pyplot as plt
from openpiv import pyprocess, tools
import pkg_resources as pkg
# import numpy as np
import matplotlib.animation as animation
"""This module contains image processing routines that improve
images prior to PIV processing."""
__licence_ = """
Copyright (C) 2011 www.openpiv.net
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
[docs]def simple_piv(im1, im2, plot=True):
"""
Simplest PIV run on the pair of images using default settings
piv(im1,im2) will create a tmp.vec file with the vector filed in pix/dt
(dt=1) from two images, im1,im2 provided as full path filenames
(TIF is preferable, whatever imageio can read)
"""
if isinstance(im1, str):
im1 = tools.imread(im1)
im2 = tools.imread(im2)
u, v, s2n = pyprocess.extended_search_area_piv(
im1.astype(np.int32), im2.astype(np.int32), window_size=32,
overlap=16, search_area_size=32
)
x, y = pyprocess.get_coordinates(image_size=im1.shape,
search_area_size=32, overlap=16)
valid = s2n > np.percentile(s2n, 5)
if plot:
_, ax = plt.subplots(figsize=(6, 6))
ax.imshow(im1, cmap=plt.get_cmap("gray"), alpha=0.5, origin="upper")
ax.quiver(x[valid], y[valid], u[valid], -v[valid], scale=70,
color='r', width=.005)
plt.show()
# conform with the windef and tools.display_vector_field
x,y,u,v = tools.transform_coordinates(x,y,u,v)
return x, y, u, v, s2n
[docs]def piv_example():
"""
PIV example uses examples/test5 vortex PIV data to show the main principles
piv(im1,im2) will create a tmp.vec file with the vector filed in pix/dt
(dt=1) from two images, im1,im2 provided as full path filenames
(TIF is preferable)
"""
# if im1 is None and im2 is None:
im1 = pkg.resource_filename("openpiv", "data/test1/exp1_001_a.bmp")
im2 = pkg.resource_filename("openpiv", "data/test1/exp1_001_b.bmp")
frame_a = tools.imread(im1)
frame_b = tools.imread(im2)
# frame_a[0:32, 512 - 32:] = 255
images = []
images.extend([frame_a, frame_b])
fig, ax = plt.subplots()
# ims is a list of lists, each row is a list of artists to draw in the
# current frame; here we are just animating one artist, the image, in
# each frame
ims = []
for i in range(2):
im = ax.imshow(images[i % 2], animated=True, cmap="gray")
ims.append([im])
_ = animation.ArtistAnimation(fig, ims, interval=500, blit=False,
repeat_delay=0)
plt.show()
# import os
vel = pyprocess.extended_search_area_piv(
frame_a.astype(np.int32), frame_b.astype(np.int32), window_size=32,
search_area_size=64,
overlap=8
)
x, y = pyprocess.get_coordinates(image_size=frame_a.shape,
search_area_size=64, overlap=8)
fig, ax = plt.subplots(1, 2, figsize=(11, 8))
ax[0].imshow(frame_a, cmap=plt.get_cmap("gray"), alpha=0.8)
ax[0].quiver(x, y, vel[0], -vel[1], scale=50, color="r")
ax[1].quiver(x, y[::-1, :], vel[0], -1*vel[1], scale=50, color="b")
ax[1].set_aspect(1)
# ax[1].invert_yaxis()
plt.show()
return x, y, vel[0], vel[1]