转载自：http://segmentfault.com/a/1190000003804797

视频的处理和图片的处理类似，只不过视频处理需要连续处理一系列图片。

一般有两种视频源，一种是直接从硬盘加载视频，另一种是获取摄像头视频。

0x00. 本地读取视频

核心函数:

cv.CaptureFromFile()

代码示例：

import cv2.cv as cvcapture = cv.CaptureFromFile('myvideo.avi')nbFrames = int(cv.GetCaptureProperty(capture, cv.CV_CAP_PROP_FRAME_COUNT))#CV_CAP_PROP_FRAME_WIDTH Width of the frames in the video stream
#CV_CAP_PROP_FRAME_HEIGHT Height of the frames in the video streamfps = cv.GetCaptureProperty(capture, cv.CV_CAP_PROP_FPS)wait = int(1/fps * 1000/1)duration = (nbFrames * fps) / 1000print 'Num. Frames = ', nbFrames
print 'Frame Rate = ', fps, 'fps'
print 'Duration = ', duration, 'sec'for f in xrange( nbFrames ):frameImg = cv.QueryFrame(capture)print cv.GetCaptureProperty(capture, cv.CV_CAP_PROP_POS_FRAMES)cv.ShowImage("The Video", frameImg)cv.WaitKey(wait)

cv2

import numpy as np
import cv2cap = cv2.VideoCapture('vtest.avi')while(cap.isOpened()):ret, frame = cap.read()gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)cv2.imshow('frame',gray)if cv2.waitKey(1) & 0xFF == ord('q'):breakcap.release()
cv2.destroyAllWindows()

0x01. 摄像头视频读取

核心函数：

cv.CaptureFromCAM()

示例代码：

import cv2.cv as cvcapture = cv.CaptureFromCAM(0)while True:frame = cv.QueryFrame(capture)cv.ShowImage("Webcam", frame)c = cv.WaitKey(1)if c == 27: #Esc on Windowsbreak

cv2

import numpy as np
import cv2cap = cv2.VideoCapture(0)while(True):# Capture frame-by-frameret, frame = cap.read()# Our operations on the frame come heregray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)# Display the resulting framecv2.imshow('frame',gray)if cv2.waitKey(1) & 0xFF == ord('q'):break# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()

0x02. 写入视频

摄像头录制视频

import cv2.cv as cvcapture=cv.CaptureFromCAM(0)
temp=cv.QueryFrame(capture)
writer=cv.CreateVideoWriter("output.avi", cv.CV_FOURCC("D", "I", "B", " "), 5, cv.GetSize(temp), 1)
#On linux I used to take "M","J","P","G" as fourcccount=0
while count<50:print countimage=cv.QueryFrame(capture)cv.WriteFrame(writer, image)cv.ShowImage('Image_Window',image)cv.WaitKey(1)count+=1

从文件中读取视频并保存

import cv2.cv as cv
capture = cv.CaptureFromFile('img/mic.avi')nbFrames = int(cv.GetCaptureProperty(capture, cv.CV_CAP_PROP_FRAME_COUNT))
width = int(cv.GetCaptureProperty(capture, cv.CV_CAP_PROP_FRAME_WIDTH))
height = int(cv.GetCaptureProperty(capture, cv.CV_CAP_PROP_FRAME_HEIGHT))
fps = cv.GetCaptureProperty(capture, cv.CV_CAP_PROP_FPS)
codec = cv.GetCaptureProperty(capture, cv.CV_CAP_PROP_FOURCC)wait = int(1/fps * 1000/1) #Compute the time to wait between each frame queryduration = (nbFrames * fps) / 1000 #Compute durationprint 'Num. Frames = ', nbFrames
print 'Frame Rate = ', fps, 'fps'writer=cv.CreateVideoWriter("img/new.avi", int(codec), int(fps), (width,height), 1) #Create writer with same parameterscv.SetCaptureProperty(capture, cv.CV_CAP_PROP_POS_FRAMES,80) #Set the number of framesfor f in xrange( nbFrames - 80 ): #Just recorded the 80 first frames of the videoframe = cv.QueryFrame(capture)print cv.GetCaptureProperty(capture, cv.CV_CAP_PROP_POS_FRAMES)cv.WriteFrame(writer, frame)cv.WaitKey(wait)

cv2

import numpy as np
import cv2cap = cv2.VideoCapture(0)# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))while(cap.isOpened()):ret, frame = cap.read()if ret==True:frame = cv2.flip(frame,0)# write the flipped frameout.write(frame)cv2.imshow('frame',frame)if cv2.waitKey(1) & 0xFF == ord('q'):breakelse:break# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()