OpenCV 读写视频

用户6021899

发布于 2019-08-28 11:37:34

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发布于 2019-08-28 11:37:34

文章被收录于专栏：Python编程 pyqt matplotlibPython编程 pyqt matplotlib

OpenCV读视频前首先需要创建VideoCapture对象：

import cv2
import numpy as np

videoCapture = cv2.VideoCapture("girl.mp4") # 创建VideoCapture对象，用于读取视频

接着获取视频的一些基本信息:

fps = videoCapture.get(cv2.CAP_PROP_FPS)#获取帧率(每秒播放几张图像）
#获取宽高
size = (int(videoCapture.get(cv2.CAP_PROP_FRAME_WIDTH)),
        int(videoCapture.get(cv2.CAP_PROP_FRAME_HEIGHT)))
fNUMS = videoCapture.get(cv2.CAP_PROP_FRAME_COUNT) #获取帧数

若是写视频（无声音），则需要创建VideoWriter对象：

#创建VideoWriter对象，用于写视频
#videoWriter = cv2.VideoWriter("douyin.avi", cv2.VideoWriter_fourcc('I', '4','2','0'), int(fps), newSize) #此格式文件大
videoWriter = cv2.VideoWriter("douyin.avi", cv2.VideoWriter_fourcc('X', 'V','I','D'), int(fps), newSize)

我们可以自定义视频的显示尺寸：

newSize = (300,650) # 自己设定的缩放后的图像宽高

最后，循环读入每一帧，显示在屏幕上，并写入进新的视频文件：

success, frame = videoCapture.read() # 读取一帧，返回是否成功和该帧图像数组
while success and cv2.waitKey(1) == -1: #如果成功读取，且没按下ESC键
    frame_resized = cv2.resize(frame, newSize) #图像缩放
    mirrorred = frame_resized[:, : :-1,:] # 左右镜像
    cv2.imshow("original", frame_resized)
    cv2.imshow("mirrorred", mirrorred)
    videoWriter.write(mirrorred)#写入一帧
   
    cv2.waitKey(int(1000/int(fps))) #延迟
    success, frame = videoCapture.read()#读取下一帧
    
cv2.waitKey()
cv2.destroyAllWindows()
videoCapture.release()#释放资源

下面是完整的代码，里面额外添加了一些边缘检测，求帧差，镜像，添加文字等功能。（上传的动图像素差是腾讯的锅，压缩得太厉害）

import cv2
import numpy as np
from edge import strokeEdges #自定义的边缘检测函数（之前有介绍）

videoCapture = cv2.VideoCapture("girl.mp4") # 创建VideoCapture对象，用于读取视频
fps = videoCapture.get(cv2.CAP_PROP_FPS)#获取帧率(每秒播放几张图像）
#获取宽高
size = (int(videoCapture.get(cv2.CAP_PROP_FRAME_WIDTH)),
        int(videoCapture.get(cv2.CAP_PROP_FRAME_HEIGHT)))
fNUMS = videoCapture.get(cv2.CAP_PROP_FRAME_COUNT) #获取帧数
newSize = (300,650) # 自己设定的缩放后的图像宽高
#创建VideoWriter对象，用于写视频
#videoWriter = cv2.VideoWriter("douyin.avi", cv2.VideoWriter_fourcc('I', '4','2','0'), int(fps), newSize) #文件大
videoWriter = cv2.VideoWriter("douyin.avi", cv2.VideoWriter_fourcc('X', 'V','I','D'), int(fps), newSize)
success, frame = videoCapture.read() # 读取一帧，返回是否成功和该帧图像数组
lastFrame = np.zeros((newSize[1], newSize[0], 3)) #
while success and cv2.waitKey(1) == -1:
    frame_resized = cv2.resize(frame, newSize)
    edges = strokeEdges(frame_resized,blurKsize=1, edgeKsize=5) #两个ksize须为奇数
    grayEdges = cv2.cvtColor(edges,cv2.COLOR_BGR2GRAY)#转灰度图
   
    delta =np.abs(frame_resized - lastFrame)
    grayDelta = np.mean(delta, axis =2)#转灰度图的 numpy方法，三通道取均值
    mirrorred = frame_resized[:, : :-1,:] # 左右镜像
    #在图像上添加文字（此方法不能添加中文）
    #putText(img, text, org, fontFace, fontScale, color[, thickness[, lineType[, bottomLeftOrigin]]])
    #mirrorred = cv2.putText(mirrorred,"mirrorred", (20,50), font, 1, (0,255,0), 2, 4, False)
    mirrorred = cv2.putText(mirrorred,"mirrorred", (20,50), cv2.FONT_HERSHEY_COMPLEX, 1, (0,255,0), 2, 4, False)
   
    #fliped = frame_resized[ : :-1, :,:]        #上下镜像
    #mirr_fliped = frame_resized[: : -1, : : -1, :] #左右镜像+上下镜像
   
    #同名窗口会“覆盖”掉
    cv2.imshow("original", frame_resized)
    cv2.imshow("mirrorred", mirrorred)
    #cv2.imshow("flipped", fliped)
    #cv2.imshow("mirr_flipped", mirr_fliped)
   
    #cv2.imshow("girlEdge", 255-grayEdges)
    #cv2.imshow("delta", grayDelta)
   
    lastFrame = frame_resized
    videoWriter.write(frame_resized)
   
    cv2.waitKey(int(1000/int(fps))) #延迟
    success, frame = videoCapture.read()
cv2.waitKey()
cv2.destroyAllWindows()
videoCapture.release()