# -*- coding: utf-8 -*- 

import cv2

#两个回调函数
def HoughLinesP(minLineLength):
 global minLINELENGTH 
 minLINELENGTH = minLineLength + 1
 print "minLINELENGTH:",minLineLength + 1
 tempIamge = scr.copy()
 lines = cv2.HoughLinesP( edges, 1, cv2.cv.CV_PI/180, minLINELENGTH, 0 )
 for x1,y1,x2,y2 in lines[0]:
 cv2.line(tempIamge,(x1,y1),(x2,y2),(0,255,0),1)
 cv2.imshow(window_name,tempIamge)

#临时变量
minLineLength = 20

#全局变量
minLINELENGTH = 20
max_value = 100
window_name = "HoughLines Demo"
trackbar_value = "minLineLength"

#读入图片，模式为灰度图，创建窗口
scr = cv2.imread("G:\\homework\\building.bmp")
gray = cv2.cvtColor(scr,cv2.COLOR_BGR2GRAY)
img = cv2.GaussianBlur(gray,(3,3),0)
edges = cv2.Canny(img, 50, 150, apertureSize = 3)
cv2.namedWindow(window_name)

#创建滑动条
cv2.createTrackbar( trackbar_value, window_name,   minLineLength, max_value, HoughLinesP)

#初始化
HoughLinesP(20)

if cv2.waitKey(0) == 27: 
 cv2.destroyAllWindows()

> import os
> os.chdir("g:\homework")
> 
> import HoughLines
minLINELENGTH: 20
minLINELENGTH: 21
minLINELENGTH: 22
minLINELENGTH: 23
minLINELENGTH: 25
minLINELENGTH: 26
minLINELENGTH: 27
minLINELENGTH: 28