openmv/scripts/examples/05-Feature-Detection/find_lines.py

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2.4 KiB
Python

# This work is licensed under the MIT license.
# Copyright (c) 2013-2023 OpenMV LLC. All rights reserved.
# https://github.com/openmv/openmv/blob/master/LICENSE
#
# Find Lines Example
#
# This example shows off how to find lines in the image. For each line object
# found in the image a line object is returned which includes the line's rotation.
# Note: Line detection is done by using the Hough Transform:
# http://en.wikipedia.org/wiki/Hough_transform
# Please read about it above for more information on what `theta` and `rho` are.
# find_lines() finds infinite length lines. Use find_line_segments() to find non-infinite lines.
import sensor
import time
ENABLE_LENS_CORR = False # turn on for straighter lines...
sensor.reset()
sensor.set_pixformat(sensor.RGB565) # grayscale is faster
sensor.set_framesize(sensor.QQVGA)
sensor.skip_frames(time=2000)
clock = time.clock()
# All line objects have a `theta()` method to get their rotation angle in degrees.
# You can filter lines based on their rotation angle.
min_degree = 0
max_degree = 179
# All lines also have `x1()`, `y1()`, `x2()`, and `y2()` methods to get their end-points
# and a `line()` method to get all the above as one 4 value tuple for `draw_line()`.
while True:
clock.tick()
img = sensor.snapshot()
if ENABLE_LENS_CORR:
img.lens_corr(1.8) # for 2.8mm lens...
# `threshold` controls how many lines in the image are found. Only lines with
# edge difference magnitude sums greater than `threshold` are detected...
# More about `threshold` - each pixel in the image contributes a magnitude value
# to a line. The sum of all contributions is the magintude for that line. Then
# when lines are merged their magnitudes are added together. Note that `threshold`
# filters out lines with low magnitudes before merging. To see the magnitude of
# un-merged lines set `theta_margin` and `rho_margin` to 0...
# `theta_margin` and `rho_margin` control merging similar lines. If two lines
# theta and rho value differences are less than the margins then they are merged.
for l in img.find_lines(threshold=1000, theta_margin=25, rho_margin=25):
if (min_degree <= l.theta()) and (l.theta() <= max_degree):
img.draw_line(l.line(), color=(255, 0, 0))
# print(l)
print("FPS %f" % clock.fps())
# About negative rho values:
#
# A [theta+0:-rho] tuple is the same as [theta+180:+rho].