关于opencvvideocapture的信息

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本文目录一览：

• 1、opencv中VideoCapture和cvCapture有什么区别？
• 2、OpenCV VideoCapture.get()参数详解
• 3、opencv2.4用cv::VideoCapture无法打开视频，视频路径是没错的，之前打开图片没问题，但视频却打不开
• 4、python3使用opencv的VideoCapture读取视频文件遇到Error opening file，要怎么办？
• 5、OpenCV VideoCapture解析
• 6、opencv里能用VideoCapture能打开视频但不能打开摄像头

opencv中VideoCapture和cvCapture有什么区别？

VideoCapture和cvCapture其实是一样的，你可以去看看源码，VideoCapture其实在内部调用了cvCapture。这是不同版本的opencv导致的。我接触到的opencv有过一次大升级，函数名有很多变化，其实是向着面向对象的方向发展了，也就是开始重c++而轻c了虚弯轿。

cvLoadImage和imread返回值略有差异，过去的opencv处理图像倾向差肆使用IplImage类型。升级后更倾向于将图像、矩阵等等都闹神统一使用Mat类型上。差别不大。

你看头文件也能发现imread位于highgui.hpp里面是c++，cvLoadImage位于highgui_c.h里，是c。

[img]

OpenCV VideoCapture.get()参数详解

具体属性名及英文卖燃此说明段陵按顺序如下 ：

CV_CAP_PROP_POS_MSEC Current position of the video file in milliseconds or video capture timestamp.

CV_CAP_PROP_POS_FRAMES 0-based index of the frame to be decoded/captured next.

CV_CAP_PROP_POS_AVI_RATIO Relative position of the video file: 0 - start of the film, 1 - end of the film.

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 stream.

CV_CAP_PROP_FPS Frame rate.

CV_CAP_PROP_FOURCC 4-character code of codec.

CV_CAP_PROP_FRAME_COUNT Number of frames in the video file.

CV_CAP_PROP_FORMAT Format of the Mat objects returned by retrieve() .

CV_CAP_PROP_MODE Backend-specific value indicating the current capture mode.

CV_CAP_PROP_BRIGHTNESS Brightness of the image (only for cameras).

CV_CAP_PROP_CONTRAST Contrast of the image (only for cameras).

CV_CAP_PROP_SATURATION Saturation of the image (only for cameras).

CV_CAP_PROP_HUE Hue of the image (only for cameras).

CV_CAP_PROP_GAIN Gain of the image (only for cameras).

CV_CAP_PROP_EXPOSURE Exposure (only for cameras).

CV_CAP_PROP_CONVERT_RGB Boolean flags indicating whether images should be converted to RGB.

CV_CAP_PROP_WHITE_BALANCE Currently not supported

CV_CAP_PROP_RECTIFICATION Rectification flag for stereo cameras (note: only supported by DC1394 v 2.x backend currently)

Note: 如果查询的视频属性是中迅VideoCapture类不支持的，将会返回0

opencv2.4用cv::VideoCapture无法打开视频，视频路径是没错的，之前打开图片没问题，但视频却打不开

整个项目的结构图：

编写森段并DetectFaceDemo.java,代码如下：

[java] view

plaincopyprint?

package com.njupt.zhb.test;

import org.opencv.core.Core;

import org.opencv.core.Mat;

import org.opencv.core.MatOfRect;

import org.opencv.core.Point;

import org.opencv.core.Rect;

import org.opencv.core.Scalar;

import org.opencv.highgui.Highgui;

import org.opencv.objdetect.CascadeClassifier;

//

// Detects faces in an image, draws boxes around them, and writes the results

// to "faceDetection.png".

//

public class DetectFaceDemo {

public void run() {

System.out.println("\nRunning DetectFaceDemo");

System.out.println(getClass().getResource("lbpcascade_frontalface.xml").getPath());

// Create a face detector from the cascade file in the resources

// directory.

//CascadeClassifier faceDetector = new CascadeClassifier(getClass().getResource("lbpcascade_frontalface.xml").getPath());

//Mat image = Highgui.imread(getClass().getResource("lena.png").getPath());

//注意：源程序的路径会多打印一个‘/’，因此总是出现燃竖如下错误

/*

* Detected 0 faces Writing faceDetection.png libpng warning: Image

* width is zero in IHDR libpng warning: Image height is zero in IHDR

* libpng error: Invalid IHDR data

*/

//因此，我此迹们将第一个字符去掉

String xmlfilePath=getClass().getResource("lbpcascade_frontalface.xml").getPath().substring(1);

CascadeClassifier faceDetector = new CascadeClassifier(xmlfilePath);

Mat image = Highgui.imread(getClass().getResource("we.jpg").getPath().substring(1));

// Detect faces in the image.

// MatOfRect is a special container class for Rect.

MatOfRect faceDetections = new MatOfRect();

faceDetector.detectMultiScale(image, faceDetections);

System.out.println(String.format("Detected %s faces", faceDetections.toArray().length));

// Draw a bounding box around each face.

for (Rect rect : faceDetections.toArray()) {

Core.rectangle(image, new Point(rect.x, rect.y), new Point(rect.x + rect.width, rect.y + rect.height), new Scalar(0, 255, 0));

}

// Save the visualized detection.

String filename = "faceDetection.png";

System.out.println(String.format("Writing %s", filename));

Highgui.imwrite(filename, image);

}

}

package com.njupt.zhb.test;

import org.opencv.core.Core;

import org.opencv.core.Mat;

import org.opencv.core.MatOfRect;

import org.opencv.core.Point;

import org.opencv.core.Rect;

import org.opencv.core.Scalar;

import org.opencv.highgui.Highgui;

import org.opencv.objdetect.CascadeClassifier;

//

// Detects faces in an image, draws boxes around them, and writes the results

// to "faceDetection.png".

//

public class DetectFaceDemo {

public void run() {

System.out.println("\nRunning DetectFaceDemo");

System.out.println(getClass().getResource("lbpcascade_frontalface.xml").getPath());

// Create a face detector from the cascade file in the resources

// directory.

//CascadeClassifier faceDetector = new CascadeClassifier(getClass().getResource("lbpcascade_frontalface.xml").getPath());

//Mat image = Highgui.imread(getClass().getResource("lena.png").getPath());

//注意：源程序的路径会多打印一个‘/’，因此总是出现如下错误

/*

* Detected 0 faces Writing faceDetection.png libpng warning: Image

* width is zero in IHDR libpng warning: Image height is zero in IHDR

* libpng error: Invalid IHDR data

*/

//因此，我们将第一个字符去掉

String xmlfilePath=getClass().getResource("lbpcascade_frontalface.xml").getPath().substring(1);

CascadeClassifier faceDetector = new CascadeClassifier(xmlfilePath);

Mat image = Highgui.imread(getClass().getResource("we.jpg").getPath().substring(1));

// Detect faces in the image.

// MatOfRect is a special container class for Rect.

MatOfRect faceDetections = new MatOfRect();

faceDetector.detectMultiScale(image, faceDetections);

System.out.println(String.format("Detected %s faces", faceDetections.toArray().length));

// Draw a bounding box around each face.

for (Rect rect : faceDetections.toArray()) {

Core.rectangle(image, new Point(rect.x, rect.y), new Point(rect.x + rect.width, rect.y + rect.height), new Scalar(0, 255, 0));

}

// Save the visualized detection.

String filename = "faceDetection.png";

System.out.println(String.format("Writing %s", filename));

Highgui.imwrite(filename, image);

}

}

3.编写测试类：

[java] view

plaincopyprint?

package com.njupt.zhb.test;

public class TestMain {

public static void main(String[] args) {

System.out.println("Hello, OpenCV");

// Load the native library.

System.loadLibrary("opencv_java246");

new DetectFaceDemo().run();

}

}

//运行结果:

//Hello, OpenCV

//

//Running DetectFaceDemo

///E:/eclipse_Jee/workspace/JavaOpenCV246/bin/com/njupt/zhb/test/lbpcascade_frontalface.xml

//Detected 8 faces

//Writing faceDetection.png

package com.njupt.zhb.test;

public class TestMain {

public static void main(String[] args) {

System.out.println("Hello, OpenCV");

// Load the native library.

System.loadLibrary("opencv_java246");

new DetectFaceDemo().run();

}

}

//运行结果:

//Hello, OpenCV

//

//Running DetectFaceDemo

///E:/eclipse_Jee/workspace/JavaOpenCV246/bin/com/njupt/zhb/test/lbpcascade_frontalface.xml

//Detected 8 faces

//Writing faceDetection.png

python3使用opencv的VideoCapture读取视频文件遇到Error opening file，要怎么办？

Thanks for your 数颂share^

a=r"D:\Desktop\py\1.avi"   #another way to fix the warning

a=r"岁派D:\Desktop\py\1.avi".replace('薯雀郑\\','/')   #this may be better

OpenCV VideoCapture解析

1、cap = cv2.VideoCapture(0)VideoCapture()中参数是0，表示打开笔记本的内置摄像头，参数是视频文件路径则打开视频，如cap = cv2.VideoCapture("../test.avi"滑和)

2、ret,frame = cap.read() cap.read()按帧读取视频，ret,frame是获cap.read()方法的两个返回值。其中ret是布尔值，如果读取帧是正确的则返回True，如棚让兆果文件读取到结尾，它的返回值就为False。frame就是每一帧的图像，是个三维矩阵。

3、cv2.waitKey(1)，waitKey（）方法本身表示等待键盘输入，参数是1，表示延时1ms切换到下一帧图像，对于视频而言；参数为0，如cv2.waitKey(0)只显示当前帧图像，相当于视频暂停,；参数过大如cv2.waitKey(1000)，会因为延时过久而卡顿感觉到卡顿。c得到的是键盘输入的ASCII码，esc键对应的ASCII码是27，即当按esc键链租是if条件句成立

4、调用release()释放摄像头，调用destroyAllWindows()关闭所有图像窗口。

原文链接：

opencv里能用VideoCapture能打开视频但不能打开摄像头

你这个程序只是打开视频，并没有读取和显乎念示每帧的图像。用下面这个程序试试，刚试过，可以用。

int main()

{

VideoCapture capture(0);

Mat frame;

if (capture.isOpened())

{

while(1)

{

namedWindow("1", 1);

capture  搏键frame;

imshow("1", frame);

waitKey(10);

}

}

waitKey(0);

return 0;

}

我用的是VS2013，岁银困opencv2.4.11

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