def lineIntersection(line1, line2):
'''
Finds the intersection point of two 2D lines in (r, theta) form,
where the line is parallel to the vector denoted by (r, theta)
'''
p1a = x1, y1 = toXY(line1)
p1b = x1 - y1, x1 + y1
p2a = x3, y3 = toXY(line2)
p2b = x3 - y3, x3 + y3
return util.lineIntersectionPoints(p1a, p1b, p2a, p2b)
def lineIntersection(line1, line2):
'''
Finds the intersection point of two 2D lines in (r, theta) form,
where the line is parallel to the vector denoted by (r, theta)
'''
p1a = x1, y1 = toXY(line1)
p1b = x1-y1, x1+y1
p2a = x3, y3 = toXY(line2)
p2b = x3-y3, x3+y3
return util.lineIntersectionPoints(p1a, p1b, p2a, p2b)
def lineToVisibleSegment(line, threshold_img, eps=1e-8):
'''
Returns the two endpoints of the line segment in the frame
line is in (r, theta) form
return value is two points in ((x1, y1) (x2, y2)), where x1 <= x2
'''
width, height = cv.GetSize(threshold_img)
# Get two points on the line
p1a = x1, y1 = toXY(line)
p1b = x1 - y1, x1 + y1
# Find top-left point a
# First try to intersect with each edge of image
candidates = [
util.lineIntersectionPoints(p1a, p1b, (0, 0), (width, 0)),
util.lineIntersectionPoints(p1a, p1b, (0, 0), (0, height)),
util.lineIntersectionPoints(p1a, p1b, (0, height), (width, height)),
util.lineIntersectionPoints(p1a, p1b, (width, 0), (width, height))
]
# There should be only 2 intersection points with the image rectangle,
# (or 1 if it's tangent to a corner, or inf if it lies on an edge, but
# we'll ignore those cases for now since they're improbable)
# Expand bounds by epsilon=1e-8 to account for floating point imprecision
points = filter(lambda x: (-eps <= x[0] <= width+eps) \
and (-eps <= x[1] <= height+eps),
candidates)
if len(points) != 2:
print 'Line is not within in image bounds!'
return None
# Try to iterate over pixel values starting at points[0]
m = x1 / -y1 if y1 != 0 else float('inf')
b = m * -x1 + y1
startPt = None
endPt = None
# Line is more horizontal: iterate over x values
if m < 1:
# Ensure that point[0] is leftmost point
if points[0][0] > points[1][0]:
points[0], points[1] = points[1], points[0]
# Look for start point from leftmost point
x, y = points[0]
while x < points[1][0] and startPt is None:
if getPx(threshold_img, x, y) != 0:
startPt = (x, y)
x += 1
y = m * x + b
# Look for end point from rightmost point
x, y = points[1]
while x > points[0][0] and endPt is None:
if getPx(threshold_img, x, y) != 0:
endPt = (x, y)
x -= 1
y = m * x + b
# Line is more vertical: iterate over y values
else:
m = y1 / x1
b = m * -y1 + x1
# Ensure that point[0] is topmost point
if points[0][1] > points[1][1]:
points[0], points[1] = points[1], points[0]
# Look for start point from topmost point
x, y = points[0]
while y < points[1][1] and startPt is None:
if getPx(threshold_img, x, y) != 0:
startPt = (x, y)
y += 1
x = m * y + b
x, y = points[1]
while y < points[0][1] and endPt is None:
if getPx(threshold_img, x, y) != 0:
endPt = (x, y)
y -= 1
x = m * y + b
if startPt is None or endPt is None:
print 'Line segment not found: startPt=%s, endPt=%s' % (startPt, endPt)
return None
return startPt, endPt
def lineToVisibleSegment(line, threshold_img, eps=1e-8):
'''
Returns the two endpoints of the line segment in the frame
line is in (r, theta) form
return value is two points in ((x1, y1) (x2, y2)), where x1 <= x2
'''
width, height = cv.GetSize(threshold_img)
# Get two points on the line
p1a = x1, y1 = toXY(line)
p1b = x1-y1, x1+y1
# Find top-left point a
# First try to intersect with each edge of image
candidates = [util.lineIntersectionPoints(p1a, p1b, (0, 0), (width, 0)),
util.lineIntersectionPoints(p1a, p1b, (0, 0), (0, height)),
util.lineIntersectionPoints(p1a, p1b, (0, height), (width, height)),
util.lineIntersectionPoints(p1a, p1b, (width, 0), (width, height))]
# There should be only 2 intersection points with the image rectangle,
# (or 1 if it's tangent to a corner, or inf if it lies on an edge, but
# we'll ignore those cases for now since they're improbable)
# Expand bounds by epsilon=1e-8 to account for floating point imprecision
points = filter(lambda x: (-eps <= x[0] <= width+eps) \
and (-eps <= x[1] <= height+eps),
candidates)
if len(points) != 2:
print 'Line is not within in image bounds!'
return None
# Try to iterate over pixel values starting at points[0]
m = x1 / -y1 if y1 != 0 else float('inf')
b = m * -x1 + y1
startPt = None
endPt = None
# Line is more horizontal: iterate over x values
if m < 1:
# Ensure that point[0] is leftmost point
if points[0][0] > points[1][0]:
points[0], points[1] = points[1], points[0]
# Look for start point from leftmost point
x, y = points[0]
while x < points[1][0] and startPt is None:
if getPx(threshold_img, x, y) != 0:
startPt = (x, y)
x += 1
y = m * x + b
# Look for end point from rightmost point
x, y = points[1]
while x > points[0][0] and endPt is None:
if getPx(threshold_img, x, y) != 0:
endPt = (x, y)
x -= 1
y = m * x + b
# Line is more vertical: iterate over y values
else:
m = y1 / x1
b = m * -y1 + x1
# Ensure that point[0] is topmost point
if points[0][1] > points[1][1]:
points[0], points[1] = points[1], points[0]
# Look for start point from topmost point
x, y = points[0]
while y < points[1][1] and startPt is None:
if getPx(threshold_img, x, y) != 0:
startPt = (x, y)
y += 1
x = m * y + b
x, y = points[1]
while y < points[0][1] and endPt is None:
if getPx(threshold_img, x, y) != 0:
endPt = (x, y)
y -= 1
x = m * y + b
if startPt is None or endPt is None:
print 'Line segment not found: startPt=%s, endPt=%s' % (startPt, endPt)
return None
return startPt, endPt