"""Hough transform module."""
from math import pi
from PIL import Image
import pcf
[docs]class Hough:
"""Hough transform.
This class stores the parameters of the transformation.
"""
def __init__(self, size, dt, init_angle):
self.size = size # this is a tuple (width, height)
self.dt = dt # this is the angle step in hough transform
self.initial_angle = init_angle
@classmethod
[docs] def default(cls, image):
"""Default parameters for Hough transform of the *image*."""
size = image.size
dt = pi / size[1]
initial_angle = (pi / 4) + (dt / 2)
return cls(size, dt, initial_angle)
def transform(self, image):
image_s = pcf.hough(self.size, image.tobytes(), self.initial_angle,
self.dt)
image_t = Image.frombytes('L', self.size, image_s)
return image_t
def apply_filter(self, filter_f):
return Hough(self.size, self.dt, self.initial_angle,
filter_f(self.image))
[docs] def lines_from_list(self, p_list):
"""Take a list of transformed points and return a list of corresponding
lines as (angle, distance) tuples."""
# TODO! why is distance allways integer?
lines = []
for p in p_list:
lines.append(self.angle_distance(p))
return lines
def all_lines_h(self, image):
# TODO what is this?
im_l = image.load()
lines1 = []
for x in xrange(self.size[0] / 2):
for y in xrange(self.size[1]):
if im_l[x, y]:
lines1.append(self.angle_distance((x, y)))
lines2 = []
for x in xrange(self.size[0] / 2, self.size[0]):
for y in xrange(self.size[1]):
if im_l[x, y]:
lines2.append(self.angle_distance((x, y)))
return [lines1, lines2]
def all_lines(self):
# TODO what is this? how does it differ from the upper one?
im_l = self.image.load()
lines = []
for x in xrange(self.size[0]):
for y in xrange(self.size[1]):
if im_l[x, y]:
lines.append(self.angle_distance((x, y)))
return lines
[docs] def angle_distance(self, point):
"""Take a point from the transformed image and return the corresponding
line in the original as (angle, distance) tuple."""
return (self.dt * point[1] + self.initial_angle,
point[0] - self.size[0] / 2)