用opencv来读写视频文件（C++/Python）

读取视频

Python

1	cap = cv2.VideoCapture('chaplin.mp4')

C++

1	VideoCapture cap("chaplin.mp4");

创建VideoCapture对象后，我们就可以把视频里的每一帧读取出来

Displaying a video

读取视频文件之后，我们就可以把视频的每一帧展示出来。

Python

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import cv2 import numpy as np # Create a VideoCapture object and read from input file # If the input is the camera, pass 0 instead of the video file name cap = cv2.VideoCapture('chaplin.mp4') # Check if camera opened successfully if (cap.isOpened()== False): print("Error opening video stream or file") # Read until video is completed while(cap.isOpened()): # Capture frame-by-frame ret, frame = cap.read() if ret == True: # Display the resulting frame cv2.imshow('Frame',frame) # Press Q on keyboard to exit if cv2.waitKey(25) & 0xFF == ord('q'): break # Break the loop else: break # When everything done, release the video capture object cap.release() # Closes all the frames cv2.destroyAllWindows()

C++

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#include "opencv2/opencv.hpp" #include using namespace std; using namespace cv; int main(){ // Create a VideoCapture object and open the input file // If the input is the web camera, pass 0 instead of the video file name VideoCapture cap("chaplin.mp4"); // Check if camera opened successfully if(!cap.isOpened()){ cout << "Error opening video stream or file" << endl; return -1; } while(1){ Mat frame; // Capture frame-by-frame cap >> frame; // If the frame is empty, break immediately if (frame.empty()) break; // Display the resulting frame imshow( "Frame", frame ); // Press ESC on keyboard to exit char c=(char)waitKey(25); if(c==27) break; } // When everything done, release the video capture object cap.release(); // Closes all the frames destroyAllWindows(); return 0; }

保存视频文件

Python

1	out = cv2.VideoWriter('outpy.avi',cv2.VideoWriter_fourcc('M','J','P','G'), 10, (frame_width,frame_height))

C++

1	VideoWriter video("outcpp.avi",CV_FOURCC('M','J','P','G'),10, Size(frame_width,frame_height));

FourCC 用来制定视频编码。 详情可参考 fourcc.org!

Python

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import cv2 import numpy as np # Create a VideoCapture object cap = cv2.VideoCapture(0) # Check if camera opened successfully if (cap.isOpened() == False): print("Unable to read camera feed") # Default resolutions of the frame are obtained.The default resolutions are system dependent. # We convert the resolutions from float to integer. frame_width = int(cap.get(3)) frame_height = int(cap.get(4)) # Define the codec and create VideoWriter object.The output is stored in 'outpy.avi' file. out = cv2.VideoWriter('outpy.avi',cv2.VideoWriter_fourcc('M','J','P','G'), 10, (frame_width,frame_height)) while(True): ret, frame = cap.read() if ret == True: # Write the frame into the file 'output.avi' out.write(frame) # Display the resulting frame cv2.imshow('frame',frame) # Press Q on keyboard to stop recording if cv2.waitKey(1) & 0xFF == ord('q'): break # Break the loop else: break # When everything done, release the video capture and video write objects cap.release() out.release() # Closes all the frames cv2.destroyAllWindows()

C++

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#include "opencv2/opencv.hpp" #include using namespace std; using namespace cv; int main(){ // Create a VideoCapture object and use camera to capture the video VideoCapture cap(0); // Check if camera opened successfully if(!cap.isOpened()) { cout << "Error opening video stream" << endl; return -1; } // Default resolution of the frame is obtained.The default resolution is system dependent. int frame_width = cap.get(CV_CAP_PROP_FRAME_WIDTH); int frame_height = cap.get(CV_CAP_PROP_FRAME_HEIGHT); // Define the codec and create VideoWriter object.The output is stored in 'outcpp.avi' file. VideoWriter video("outcpp.avi",CV_FOURCC('M','J','P','G'),10, Size(frame_width,frame_height)); while(1) { Mat frame; // Capture frame-by-frame cap >> frame; // If the frame is empty, break immediately if (frame.empty()) break; // Write the frame into the file 'outcpp.avi' video.write(frame); // Display the resulting frame imshow( "Frame", frame ); // Press ESC on keyboard to exit char c = (char)waitKey(1); if( c == 27 ) break; } // When everything done, release the video capture and write object cap.release(); video.release(); // Closes all the windows destroyAllWindows(); return 0; }

Hello World

 Posted on 2018-02-21

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