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"""
Add vectors
===========
This example generates an image of vectors
Vector data is an array of shape (N, 4)
Each vector position is defined by an (x, y, x-proj, y-proj) element where
* x and y are the center points
* x-proj and y-proj are the vector projections at each center
.. tags:: visualization-basic
"""
import numpy as np
from skimage import data
import napari
# create the viewer and window
viewer = napari.Viewer()
layer = viewer.add_image(data.camera(), name='photographer')
# sample vector coord-like data
n = 200
pos = np.zeros((n, 2, 2), dtype=np.float32)
phi_space = np.linspace(0, 4 * np.pi, n)
radius_space = np.linspace(0, 100, n)
# assign x-y position
pos[:, 0, 0] = radius_space * np.cos(phi_space) + 300
pos[:, 0, 1] = radius_space * np.sin(phi_space) + 256
# assign x-y projection
pos[:, 1, 0] = 2 * radius_space * np.cos(phi_space)
pos[:, 1, 1] = 2 * radius_space * np.sin(phi_space)
# add the vectors
layer = viewer.add_vectors(pos, edge_width=3)
if __name__ == '__main__':
napari.run()
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