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canny-slow.py
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canny-slow.py
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import scipy.ndimage as ndi
import scipy
import numpy
import Image
import math
from math import pi
sigma = 2.2
f = 'lena_std.tif'
img = Image.open(f).convert('L') #grayscale
imgdata = numpy.array(img, dtype = float)
G = ndi.filters.gaussian_filter(imgdata, sigma) #gaussian low pass filter
sobelout = Image.new('L', img.size) #empty image
gradx = numpy.array(sobelout, dtype = float)
grady = numpy.array(sobelout, dtype = float)
sobel_x = [[-1,0,1],
[-2,0,2],
[-1,0,1]]
sobel_y = [[-1,-2,-1],
[0,0,0],
[1,2,1]]
width = img.size[1]
height = img.size[0]
#calculate |G| and dir(G)
for x in range(1, width-1):
for y in range(1, height-1):
px = (sobel_x[0][0] * G[x-1][y-1]) + (sobel_x[0][1] * G[x][y-1]) + \
(sobel_x[0][2] * G[x+1][y-1]) + (sobel_x[1][0] * G[x-1][y]) + \
(sobel_x[1][1] * G[x][y]) + (sobel_x[1][2] * G[x+1][y]) + \
(sobel_x[2][0] * G[x-1][y+1]) + (sobel_x[2][1] * G[x][y+1]) + \
(sobel_x[2][2] * G[x+1][y+1])
py = (sobel_y[0][0] * G[x-1][y-1]) + (sobel_y[0][1] * G[x][y-1]) + \
(sobel_y[0][2] * G[x+1][y-1]) + (sobel_y[1][0] * G[x-1][y]) + \
(sobel_y[1][1] * G[x][y]) + (sobel_y[1][2] * G[x+1][y]) + \
(sobel_y[2][0] * G[x-1][y+1]) + (sobel_y[2][1] * G[x][y+1]) + \
(sobel_y[2][2] * G[x+1][y+1])
gradx[x][y] = px
grady[x][y] = py
sobeloutmag = scipy.hypot(gradx, grady)
sobeloutdir = scipy.arctan2(grady, gradx)
scipy.misc.imsave('cannynewmag.jpg', sobeloutmag)
scipy.misc.imsave('cannynewdir.jpg', sobeloutdir)
for x in range(width):
for y in range(height):
if (sobeloutdir[x][y]<22.5 and sobeloutdir[x][y]>=0) or \
(sobeloutdir[x][y]>=157.5 and sobeloutdir[x][y]<202.5) or \
(sobeloutdir[x][y]>=337.5 and sobeloutdir[x][y]<=360):
sobeloutdir[x][y]=0
elif (sobeloutdir[x][y]>=22.5 and sobeloutdir[x][y]<67.5) or \
(sobeloutdir[x][y]>=202.5 and sobeloutdir[x][y]<247.5):
sobeloutdir[x][y]=45
elif (sobeloutdir[x][y]>=67.5 and sobeloutdir[x][y]<112.5)or \
(sobeloutdir[x][y]>=247.5 and sobeloutdir[x][y]<292.5):
sobeloutdir[x][y]=90
else:
sobeloutdir[x][y]=135
scipy.misc.imsave('cannynewdirquantize.jpg', sobeloutdir)
mag_sup = sobeloutmag.copy()
for x in range(1, width-1):
for y in range(1, height-1):
if sobeloutdir[x][y]==0:
if (sobeloutmag[x][y]<=sobeloutmag[x][y+1]) or \
(sobeloutmag[x][y]<=sobeloutmag[x][y-1]):
mag_sup[x][y]=0
elif sobeloutdir[x][y]==45:
if (sobeloutmag[x][y]<=sobeloutmag[x-1][y+1]) or \
(sobeloutmag[x][y]<=sobeloutmag[x+1][y-1]):
mag_sup[x][y]=0
elif sobeloutdir[x][y]==90:
if (sobeloutmag[x][y]<=sobeloutmag[x+1][y]) or \
(sobeloutmag[x][y]<=sobeloutmag[x-1][y]):
mag_sup[x][y]=0
else:
if (sobeloutmag[x][y]<=sobeloutmag[x+1][y+1]) or \
(sobeloutmag[x][y]<=sobeloutmag[x-1][y-1]):
mag_sup[x][y]=0
scipy.misc.imsave('cannynewmagsup.jpg', mag_sup)
m = numpy.max(mag_sup)
th = 0.2*m
tl = 0.1*m
gnh = numpy.zeros((width, height))
gnl = numpy.zeros((width, height))
for x in range(width):
for y in range(height):
if mag_sup[x][y]>=th:
gnh[x][y]=mag_sup[x][y]
if mag_sup[x][y]>=tl:
gnl[x][y]=mag_sup[x][y]
scipy.misc.imsave('cannynewgnlbeforeminus.jpg', gnl)
gnl = gnl-gnh
scipy.misc.imsave('cannynewgnlafterminus.jpg', gnl)
scipy.misc.imsave('cannynewgnh.jpg', gnh)
def traverse(i, j):
x = [-1, 0, 1, -1, 1, -1, 0, 1]
y = [-1, -1, -1, 0, 0, 1, 1, 1]
for k in range(8):
if gnh[i+x[k]][j+y[k]]==0 and gnl[i+x[k]][j+y[k]]!=0:
gnh[i+x[k]][j+y[k]]=1
traverse(i+x[k], j+y[k])
for i in range(1, width-1):
for j in range(1, height-1):
if gnh[i][j]:
gnh[i][j]=1
traverse(i, j)
scipy.misc.imsave('cannynewout.jpg', gnh)