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#!/usr/bin/python
"""
This program is a demonstration of ellipse fitting.
Trackbar controls threshold parameter.
Gray lines are contours. Colored lines are fit ellipses.
Original C implementation by: Denis Burenkov.
Python implementation by: Roman Stanchak, James Bowman
"""
import sys
import urllib2
import random
import cv2.cv as cv
def contour_iterator(contour):
while contour:
yield contour
contour = contour.h_next()
class FitEllipse:
def __init__(self, source_image, slider_pos):
self.source_image = source_image
cv.CreateTrackbar("Threshold", "Result", slider_pos, 255, self.process_image)
self.process_image(slider_pos)
def process_image(self, slider_pos):
"""
This function finds contours, draws them and their approximation by ellipses.
"""
stor = cv.CreateMemStorage()
# Create the destination images
image02 = cv.CloneImage(self.source_image)
cv.Zero(image02)
image04 = cv.CreateImage(cv.GetSize(self.source_image), cv.IPL_DEPTH_8U, 3)
cv.Zero(image04)
# Threshold the source image. This needful for cv.FindContours().
cv.Threshold(self.source_image, image02, slider_pos, 255, cv.CV_THRESH_BINARY)
# Find all contours.
cont = cv.FindContours(image02,
stor,
cv.CV_RETR_LIST,
cv.CV_CHAIN_APPROX_NONE,
(0, 0))
for c in contour_iterator(cont):
# Number of points must be more than or equal to 6 for cv.FitEllipse2
if len(c) >= 6:
# Copy the contour into an array of (x,y)s
PointArray2D32f = cv.CreateMat(1, len(c), cv.CV_32FC2)
for (i, (x, y)) in enumerate(c):
PointArray2D32f[0, i] = (x, y)
# Draw the current contour in gray
gray = cv.CV_RGB(100, 100, 100)
cv.DrawContours(image04, c, gray, gray,0,1,8,(0,0))
# Fits ellipse to current contour.
(center, size, angle) = cv.FitEllipse2(PointArray2D32f)
# Convert ellipse data from float to integer representation.
center = (cv.Round(center[0]), cv.Round(center[1]))
size = (cv.Round(size[0] * 0.5), cv.Round(size[1] * 0.5))
# Draw ellipse in random color
color = cv.CV_RGB(random.randrange(256),random.randrange(256),random.randrange(256))
cv.Ellipse(image04, center, size,
angle, 0, 360,
color, 2, cv.CV_AA, 0)
# Show image. HighGUI use.
cv.ShowImage( "Result", image04 )
if __name__ == '__main__':
if len(sys.argv) > 1:
source_image = cv.LoadImage(sys.argv[1], cv.CV_LOAD_IMAGE_GRAYSCALE)
else:
url = 'https://raw.github.com/Itseez/opencv/master/samples/c/stuff.jpg'
filedata = urllib2.urlopen(url).read()
imagefiledata = cv.CreateMatHeader(1, len(filedata), cv.CV_8UC1)
cv.SetData(imagefiledata, filedata, len(filedata))
source_image = cv.DecodeImage(imagefiledata, cv.CV_LOAD_IMAGE_GRAYSCALE)
# Create windows.
cv.NamedWindow("Source", 1)
cv.NamedWindow("Result", 1)
# Show the image.
cv.ShowImage("Source", source_image)
fe = FitEllipse(source_image, 70)
print "Press any key to exit"
cv.WaitKey(0)
cv.DestroyWindow("Source")
cv.DestroyWindow("Result")
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