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qr_extractor.py
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qr_extractor.py
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import math
import cv2
import numpy as np
BLUR_VALUE = 3
SQUARE_TOLERANCE = 0.15
AREA_TOLERANCE = 0.15
DISTANCE_TOLERANCE = 0.25
WARP_DIM = 300
SMALL_DIM = 29
def count_children(hierarchy, parent, inner=False):
if parent == -1:
return 0
elif not inner:
return count_children(hierarchy, hierarchy[parent][2], True)
return 1 + count_children(hierarchy, hierarchy[parent][0], True) + count_children(hierarchy, hierarchy[parent][2], True)
def has_square_parent(hierarchy, squares, parent):
if hierarchy[parent][3] == -1:
return False
if hierarchy[parent][3] in squares:
return True
return has_square_parent(hierarchy, squares, hierarchy[parent][3])
def get_center(c):
m = cv2.moments(c)
return [int(m["m10"] / m["m00"]), int(m["m01"] / m["m00"])]
def get_angle(p1, p2):
x_diff = p2[0] - p1[0]
y_diff = p2[1] - p1[1]
return math.degrees(math.atan2(y_diff, x_diff))
def get_midpoint(p1, p2):
return [(p1[0] + p2[0]) / 2, (p1[1] + p2[1]) / 2]
def get_farthest_points(contour, center):
distances = []
distances_to_points = {}
for point in contour:
point = point[0]
d = math.hypot(point[0] - center[0], point[1] - center[1])
distances.append(d)
distances_to_points[d] = point
distances = sorted(distances)
return [distances_to_points[distances[-1]], distances_to_points[distances[-2]]]
def line_intersection(line1, line2):
x_diff = (line1[0][0] - line1[1][0], line2[0][0] - line2[1][0])
y_diff = (line1[0][1] - line1[1][1], line2[0][1] - line2[1][1])
def det(a, b):
return a[0] * b[1] - a[1] * b[0]
div = det(x_diff, y_diff)
if div == 0:
return [-1, -1]
d = (det(*line1), det(*line2))
x = det(d, x_diff) / div
y = det(d, y_diff) / div
return [int(x), int(y)]
def extend(a, b, length, int_represent=False):
length_ab = math.sqrt((a[0] - b[0]) ** 2 + (a[1] - b[1]) ** 2)
if length_ab * length <= 0:
return b
result = [b[0] + (b[0] - a[0]) / length_ab * length, b[1] + (b[1] - a[1]) / length_ab * length]
if int_represent:
return [int(result[0]), int(result[1])]
else:
return result
def extract(frame, debug=False):
output = frame.copy()
# Remove noise and unnecessary contours from frame
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
gray = cv2.bilateralFilter(gray, 11, 17, 17)
gray = cv2.GaussianBlur(gray, (BLUR_VALUE, BLUR_VALUE), 0)
edged = cv2.Canny(gray, 30, 200)
_, contours, hierarchy = cv2.findContours(edged.copy(), cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
squares = []
square_indices = []
i = 0
for c in contours:
# Approximate the contour
peri = cv2.arcLength(c, True)
area = cv2.contourArea(c)
approx = cv2.approxPolyDP(c, 0.03 * peri, True)
# Find all quadrilateral contours
if len(approx) == 4:
# Determine if quadrilateral is a square to within SQUARE_TOLERANCE
if area > 25 and 1 - SQUARE_TOLERANCE < math.fabs((peri / 4) ** 2) / area < 1 + SQUARE_TOLERANCE and count_children(hierarchy[0], i) >= 2 and has_square_parent(hierarchy[0], square_indices, i) is False:
squares.append(approx)
square_indices.append(i)
i += 1
main_corners = []
east_corners = []
south_corners = []
tiny_squares = []
rectangles = []
# Determine if squares are QR codes
for square in squares:
area = cv2.contourArea(square)
center = get_center(square)
peri = cv2.arcLength(square, True)
similar = []
tiny = []
for other in squares:
if square[0][0][0] != other[0][0][0]:
# Determine if square is similar to other square within AREA_TOLERANCE
if math.fabs(area - cv2.contourArea(other)) / max(area, cv2.contourArea(other)) <= AREA_TOLERANCE:
similar.append(other)
elif peri / 4 / 2 > cv2.arcLength(other, True) / 4:
tiny.append(other)
if len(similar) >= 2:
distances = []
distances_to_contours = {}
for sim in similar:
sim_center = get_center(sim)
d = math.hypot(sim_center[0] - center[0], sim_center[1] - center[1])
distances.append(d)
distances_to_contours[d] = sim
distances = sorted(distances)
closest_a = distances[-1]
closest_b = distances[-2]
# Determine if this square is the top left QR code indicator
if max(closest_a, closest_b) < cv2.arcLength(square, True) * 2.5 and math.fabs(closest_a - closest_b) / max(closest_a, closest_b) <= DISTANCE_TOLERANCE:
# Determine placement of other indicators (even if code is rotated)
angle_a = get_angle(get_center(distances_to_contours[closest_a]), center)
angle_b = get_angle(get_center(distances_to_contours[closest_b]), center)
if angle_a < angle_b or (angle_b < -90 and angle_a > 0):
east = distances_to_contours[closest_a]
south = distances_to_contours[closest_b]
else:
east = distances_to_contours[closest_b]
south = distances_to_contours[closest_a]
midpoint = get_midpoint(get_center(east), get_center(south))
# Determine location of fourth corner
# Find closest tiny indicator if possible
min_dist = 10000
t = []
tiny_found = False
if len(tiny) > 0:
for tin in tiny:
tin_center = get_center(tin)
d = math.hypot(tin_center[0] - midpoint[0], tin_center[1] - midpoint[1])
if d < min_dist:
min_dist = d
t = tin
tiny_found = len(t) > 0 and min_dist < peri
diagonal = peri / 4 * 1.41421
if tiny_found:
# Easy, corner is just a few blocks away from the tiny indicator
tiny_squares.append(t)
offset = extend(midpoint, get_center(t), peri / 4 * 1.41421)
else:
# No tiny indicator found, must extrapolate corner based off of other corners instead
farthest_a = get_farthest_points(distances_to_contours[closest_a], center)
farthest_b = get_farthest_points(distances_to_contours[closest_b], center)
# Use sides of indicators to determine fourth corner
offset = line_intersection(farthest_a, farthest_b)
if offset[0] == -1:
# Error, extrapolation failed, go on to next possible code
continue
offset = extend(midpoint, offset, peri / 4 / 7)
if debug:
cv2.line(output, (farthest_a[0][0], farthest_a[0][1]), (farthest_a[1][0], farthest_a[1][1]), (0, 0, 255), 4)
cv2.line(output, (farthest_b[0][0], farthest_b[0][1]), (farthest_b[1][0], farthest_b[1][1]), (0, 0, 255), 4)
# Append rectangle, offsetting to farthest borders
rectangles.append([extend(midpoint, center, diagonal / 2, True), extend(midpoint, get_center(distances_to_contours[closest_b]), diagonal / 2, True), offset, extend(midpoint, get_center(distances_to_contours[closest_a]), diagonal / 2, True)])
east_corners.append(east)
south_corners.append(south)
main_corners.append(square)
codes = []
i = 0
for rect in rectangles:
i += 1
# Draw rectangle
vrx = np.array((rect[0], rect[1], rect[2], rect[3]), np.int32)
vrx = vrx.reshape((-1, 1, 2))
cv2.polylines(output, [vrx], True, (0, 255, 255), 1)
# Warp codes and draw them
wrect = np.zeros((4, 2), dtype="float32")
wrect[0] = rect[0]
wrect[1] = rect[1]
wrect[2] = rect[2]
wrect[3] = rect[3]
dst = np.array([
[0, 0],
[WARP_DIM - 1, 0],
[WARP_DIM - 1, WARP_DIM - 1],
[0, WARP_DIM - 1]], dtype="float32")
warp = cv2.warpPerspective(frame, cv2.getPerspectiveTransform(wrect, dst), (WARP_DIM, WARP_DIM))
# Increase contrast
warp = cv2.bilateralFilter(warp, 11, 17, 17)
warp = cv2.cvtColor(warp, cv2.COLOR_BGR2GRAY)
small = cv2.resize(warp, (SMALL_DIM, SMALL_DIM), 0, 0, interpolation=cv2.INTER_CUBIC)
_, small = cv2.threshold(small, 100, 255, cv2.THRESH_BINARY)
codes.append(small)
if debug:
cv2.imshow("Warped: " + str(i), small)
if debug:
# Draw debug information onto frame before outputting it
cv2.drawContours(output, squares, -1, (5, 5, 5), 2)
cv2.drawContours(output, main_corners, -1, (0, 0, 128), 2)
cv2.drawContours(output, east_corners, -1, (0, 128, 0), 2)
cv2.drawContours(output, south_corners, -1, (128, 0, 0), 2)
cv2.drawContours(output, tiny_squares, -1, (128, 128, 0), 2)
return codes, output