python-opencv 关于ny.array的创建以及轮廓的查找

import numpy as np

import cv2

if __name__ == '__main__':

    import sys

    try: fn = sys.argv[1]

    except: fn = 'E:\\1.BMP'

    print __doc__

    global m    #全局变量

    def callback(*argv):

         m=cv2.getTrackbarPos('select', 'forshow')

         forshow=np.zeros((h,w,3),np.uint8)#cv2接口创建矩阵

         cv2.drawContours( forshow, contours0,m, (0,0,255), 1, cv2.CV_AA, hierarchy,3  )#m为所描绘的轮廓 m = hierarchy[idx][0]

         cv2.imshow('forshow',forshow)

    img = cv2.imread(fn, 2)

    h,w=img.shape[0:2]

    contours0, hierarchy = cv2.findContours( img.copy(), cv2.RETR_TREE, cv2.CHAIN_APPROX_NONE)#参数分别为src，mode，method

                                                                                                #CV_RETR_TREE 即所有轮廓 CV_RETR_EXTERNAL 外部轮廓

                                                                                                #CV_CHAIN_APPROX_SIMPLE 只留下脚点 CV_CHAIN_APPROX_NONE 所有点

    

    forshow=np.zeros((h,w,3), np.uint8)

    cv2.namedWindow('forshow')

    cv2.createTrackbar('select', 'forshow', 0, 20, callback)#设置回调

    m=cv2.getTrackbarPos('select', 'forshow')

    cv2.drawContours( forshow, contours0,m, (0,0,255), 1, cv2.CV_AA, hierarchy,3  )   #m为所描绘的轮廓 m = hierarchy[idx][0]

    cv2.imshow('forshow',forshow)

    print hierarchy

    while True:

        ch = 0xFF & cv2.waitKey(0)

        if ch == 27:

             break
        cv2.destroyAllWindows()

通过回调函数callback来改变golba m的值，从而描绘我们所需要的轮廓