Question

我正在尝试获取第一帧并保持不变但在每次分配到另一个变量（currImage = cv.QueryFrame（capture））后它会发生变化。我做错了什么？

#!/usr/bin/env python 
# -*- coding: utf-8 -*- 

import cv

cv.NamedWindow("w1", cv.CV_WINDOW_AUTOSIZE)

#SET CAMERA INDEX BELOW
camera_index = -1 

capture = cv.CaptureFromCAM(camera_index)
isRunning = True
firstImage = cv.QueryFrame(capture)

def repeat():
  global capture #declare as globals since we are assigning to them now
  global camera_index
  global isRunning
  global firstImage
  c = cv.WaitKey(100) % 0x100
  currImage = cv.QueryFrame(capture) 
  cv.ShowImage("w1",firstImage)

  if(c==27):
    isRunning = False

while isRunning:
    repeat()

Answer 1

让我引用opencv wiki的两个段落，即这个页面：http://opencv.willowgarage.com/documentation/python/reading_and_writing_images_and_video.html

cvQueryFrame:
The function cvQueryFrame [...] is just a combination of GrabFrame and RetrieveFrame.

RetrieveFrame:
The function cvRetrieveFrame returns the pointer to the image grabbed.

您在代码中所做的不是复制对象，只是创建指向相应内存的另一个对象。对cvQueryFrame的后续调用只是修改了对象，因此你必须复制它。试着这样做：

import copy 
import cv

cv.NamedWindow("w1", cv.CV_WINDOW_AUTOSIZE)

#SET CAMERA INDEX BELOW
camera_index = -1 

capture = cv.CaptureFromCAM(camera_index)
isRunning = True
firstImage = copy.deepcopy(cv.QueryFrame(capture))

def repeat():
  global capture #declare as globals since we are assigning to them now
  global camera_index
  global isRunning
  global firstImage
  c = cv.WaitKey(100) % 0x100
  currImage = cv.QueryFrame(capture) 
  cv.ShowImage("w1",firstImage)

  if(c==27):
    isRunning = False

while isRunning:
    repeat()

currImage = cv.QueryFrame（capture）会影响其他变量

1 个答案: