def init_NNF(source_image):
"""
Return a matrix (im_shape[0] x im_shape[1] x 2) representing a random displacement field.
"""
# get the shape of the source image
im_shape = source_image.shape
#
# Generate a matrix f of size (im_shape[0] x im_shape[1] x 2) that
# assigns random X and Y displacements to each pixel
#
# We first generate a matrix of random x coordinates
x = np.random.randint(low=0,
high=im_shape[1],
size=(im_shape[0], im_shape[1]))
# Then we generate a matrix of random y coordinates
y = np.random.randint(low=0,
high=im_shape[0],
size=(im_shape[0], im_shape[1]))
# To create matrix f, we stack those two matrices
f = np.dstack((y, x))
#
# Now we generate a matrix g of size (im_shape[0] x im_shape[1] x 2)
# such that g(y,x) = [y,x]
#
g = make_coordinates_matrix(im_shape)
# define the NNF to be the difference of these two matrices
f = f - g
return f
def create_NNF_vectors_image(source, target, f, patch_size,
server=True,
subsampling=100,
line_width=0.5,
line_color='k',
tmpdir='./'):
"""
Display the nearest-neighbour field as a sparse vector field between source and target images
"""
import matplotlib.pyplot as plt
# get the shape of the source image
im_shape = source.shape
# if you are using matplotlib on a server
if server:
plt.switch_backend('agg')
import matplotlib.patches as patches
fig = plt.figure(frameon=False)
ax = plt.Axes(fig, [0., 0., 1., 1.])
ax.set_axis_off()
fig.add_axes(ax)
source = cv.cvtColor(source, cv.COLOR_BGR2RGB)
target = cv.cvtColor(target, cv.COLOR_BGR2RGB)
# create an image that contains the source and target side by side
plot_im = np.concatenate((source, target), axis=1)
ax.imshow(plot_im)
vector_coords = make_coordinates_matrix(im_shape, step=subsampling)
vshape = vector_coords.shape
vector_coords = np.reshape(vector_coords, (vshape[0] * vshape[1], 2))
for coord in vector_coords:
rect = patches.Rectangle((coord[1] - patch_size / 2.0, coord[0] - patch_size / 2.0),
patch_size,
patch_size,
linewidth=line_width,
edgecolor=line_color,
facecolor='none')
ax.add_patch(rect)
arrow = patches.Arrow(coord[1],
coord[0],
f[coord[0], coord[1], 1] + im_shape[1],
f[coord[0], coord[1], 0],
lw=line_width,
edgecolor=line_color)
ax.add_patch(arrow)
dpi = fig.dpi
fig.set_size_inches(im_shape[1] * 2 / dpi, im_shape[0] / dpi)
tmp_image = tmpdir+'/tmpvecs.png' \
fig.savefig(tmp_image)
plt.close(fig)
return tmp_image