Question

我在macbook上使用OpenCV 2.4和python 2.7.5。我想用以下代码显示内置摄像头的实时流：

import cv

cv.NamedWindow("w1", cv.CV_WINDOW_AUTOSIZE)
camera_index = 0
capture = cv.CaptureFromCAM(camera_index)

def repeat():
    global capture #declare as globals since we are assigning to them now
    global camera_index
    frame = cv.QueryFrame(capture)
    print type(frame)
    #cv.ShowImage("w1", frame)
    c = cv.WaitKey(10)
while True:
    repeat()

然而，似乎QueryFrame并不总是返回iplimage，这是我在终端上得到的：

<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'cv2.cv.iplimage'>
<type 'NoneType'>
<type 'NoneType'>
<type 'cv2.cv.iplimage'>
<type 'NoneType'>
<type 'NoneType'>
<type 'NoneType'>
<type 'cv2.cv.iplimage'>
<type 'NoneType'>
<type 'NoneType'>
<type 'cv2.cv.iplimage'>
<type 'NoneType'>

有人知道问题的来源吗？

谢谢

编辑：我注意到我的相机开启前需要几秒钟，所以在进入“while”之前我放了一些延迟。至于noneType问题，我不知道为什么每3帧我得到一个正确的图像。但是我只是通过设置条件检查我们是否得到正确的图像来“修复”它，这里是代码：

import cv

cv.NamedWindow("w1", cv.CV_WINDOW_AUTOSIZE)
camera_index = 0
capture = cv.CaptureFromCAM(camera_index)
c = cv.WaitKey(5000)
def repeat():
    global capture #declare as globals since we are assigning to them now
    global camera_index
    frame = cv.QueryFrame(capture)

    if frame:

        cv.ShowImage("w1", frame)
    c = cv.WaitKey(10)
while True:
    repeat()

Answer 1

建议如下：

camera_index = -1
放弃第一帧以防万一

firstImage = copy.deepcopy（cv.QueryFrame（capture））

分享我的代码供您参考：

import cv2 as cv
import copy
camera_index = -1 

capture = cv.CaptureFromCAM(camera_index)

isRunning = True
firstImage = copy.deepcopy(cv.QueryFrame(capture)) #drop first frame which might empty
cv.NamedWindow("Webcam",  cv.CV_WINDOW_AUTOSIZE);

def repeat():
    global capture #declare as globals since we are assigning to them now
    global camera_index
    global isRunning
    global firstImage
    currImage = cv.QueryFrame(capture) 
    cv.ShowImage("Webcam",currImage)
    c = cv.WaitKey(10)
    if(c==27):
            isRunning = False
    if (c!=-1):
            print str(c)

while isRunning:
    repeat()

OpenCV Python：QueryFrame返回None

1 个答案: