79 lines
2 KiB
Python
79 lines
2 KiB
Python
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#! /usr/bin/python
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import numpy as np
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from scipy.ndimage import label, find_objects, center_of_mass
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def find_targets(picture, threshold_blue=140, threshold_red=120, threshold_green=190, return_slices=False):
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"""Find three blue targets in the given picture (RGB matrix).
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Args:
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picture: a 2D matrix of RGB values
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threshold_blue: minimal value of the blue channel for a point to be
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considered as blue.
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threshold_red: maximal value of the red channel allowed for a
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target
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threshold_green: maximal value of the green channel allowed for a
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target
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return_slices: Boolean stating if the slices locating the targets
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should be returned.
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Returns:
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(H,L,R,[objects]) the positions of the targets in the picture (center of mass). objects is the list of slices controlled by the return_slices parameter.
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Raises:
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ValueError when less than three targets are found.
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"""
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blue_points = np.where(
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(picture[:, :, 2] > threshold_blue)
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& (picture[:, :, 0] < threshold_red)
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& (picture[:, :, 1] < threshold_green),
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1,
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0
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)
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structure = [
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[0, 1, 0],
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[1, 1, 1],
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[0, 1, 0]
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]
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labels, n = label(blue_points, structure)
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if n < 3:
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raise ValueError("Less than three potential targets were found")
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objects = [(a[0], a[1], i+1) for i, a in enumerate(find_objects(labels))]
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objects = sorted(
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objects,
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key=lambda x: (x[0].stop - x[0].start) * (x[1].stop - x[1].start)
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)[-3:]
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coordinates = center_of_mass(
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blue_points,
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labels,
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index=[o[2] for o in objects]
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)
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# Highest point
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high = sorted(
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coordinates,
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key=lambda x: x[1]
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)
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H = high[0]
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sides = sorted(
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high[1:],
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key=lambda x: x[0]
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)
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# Leftmost point
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L = sides[0]
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# Rightmost point
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R = sides[-1]
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if return_slices:
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return H, L, R, [(o[0], o[1]) for o in objects]
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else:
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return H, L, R
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