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

【问题标题】：currImage = cv.QueryFrame(capture) affects other variablescurrImage = cv.QueryFrame(capture) 影响其他变量
【发布时间】：2012-08-18 10:41:00
【问题描述】：

我正在尝试获取第一帧并保持不变，但在每次分配给另一个变量（ currImage = cv.QueryFrame(capture) ）后它都会发生变化。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()

【问题讨论】：

标签： python opencv

【解决方案1】：

让我从opencv wiki引用你的两段，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，您只是创建另一个指向相应内存的对象。对 cvQueryFrame 的后续调用只是修改对象，因此您必须复制它。尝试这样做：

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()

【讨论】：