opencv，调用摄像头对画面进行canny处理

注意canny处理的一定是灰度图像，所以先转灰度图像再处理

#include <opencv2/opencv.hpp>  

using namespace cv;

using namespace std; 

//定义视频中的帧图像，灰度帧图像和边缘检测图像

Mat frame, frame_gray, frame_canny;

int a = 70;

//cvCreateTrackbar的回调函数  

void on_trackbar(int threshold)

{
//canny边缘检测  
Canny(frame_gray, frame_canny, threshold, threshold * 3, 3);
imshow("Canny", frame_canny);

}

int main(int argc, char *argv[])

{
VideoCapture capture;
capture.open(0);
bool fromfile = false;

//Init camera  
if (!capture.isOpened())
{
cout << "capture device failed to open!" << endl;
return -1;
}

//创建窗口 
cvNamedWindow("Video", CV_WINDOW_AUTOSIZE);  //原图
cvNamedWindow("Gray", CV_WINDOW_AUTOSIZE);  //灰度图
cvNamedWindow("Canny", CV_WINDOW_AUTOSIZE);  //边缘图

capture >> frame;  //原图
cvtColor(frame, frame_gray, CV_RGB2GRAY); //灰度

while (1)
{
if (!fromfile)
capture >> frame;

cvtColor(frame, frame_gray, CV_RGB2GRAY);
imshow("Video", frame);
imshow("Gray", frame_gray);

on_trackbar(a);
if (cvWaitKey(20) == 'q')
return 1;
}

return 0;

}