Using other keys for the waitKey() function of opencv

Question

I\'m working on a program (python ,opencv) in which I use the spacebar to go to the next frame, and Esc to exit the program. These are the only two

Answer 1

As to me, the below code does't work, when it runs,the image will step to the next quickly without your press:

import cv2
img = cv2.imread('sof.jpg') # load a dummy image
while(1):
    cv2.imshow('img',img)
    k = cv2.waitKey(33)
    if k==27:    # Esc key to stop
        break
    elif k==-1:  # normally -1 returned,so don't print it
        continue
    else:
        print k # else print its value

But this works:

def test_wait_key():
    lst_img_path = [
        '/home/xy/yy_face_head/face_det_test/111.png',
        '/home/xy/yy_face_head/face_det_test/222.png'
        #.....more path ...
    ]

    for f_path in lst_img_path:
        img = cv2.imread(f_path)
        cv2.imshow('tmp', img)
        c = cv2.waitKey(0) % 256

        if c == ord('a'):
            print "pressed a"
        else:
            print 'you press %s' % chr(c)

Output as below: