【OpenCV】3rd-Canny边缘检测、打开摄像头
一、复杂的变换
1、Canny边缘检测将输出写入一个单通道（灰度级）图像（p29）
#include "cv.h"
#include "highgui.h"
IplImage* doCanny(
IplImage* in,
double lowThresh,
double highThresh,
double aperture)
{
if (in->nChannels != 1)
return(0); // Canny only handles gray scale images
IplImage* out = cvCreateImage(
cvGetSize( in ),
in->depth, //IPL_DEPTH_8U,
1);
cvCanny( in, out, lowThresh, highThresh, aperture );
return( out );
};
int main( int argc, char** argv )
{
IplImage* img_rgb = cvLoadImage( argv[1] );
IplImage* img_gry = cvCreateImage( cvSize( img_rgb->width,img_rgb->height ), img_rgb->depth, 1);
cvCvtColor(img_rgb, img_gry ,CV_BGR2GRAY);
cvNamedWindow("Example Gray", CV_WINDOW_AUTOSIZE );
cvNamedWindow("Example Canny", CV_WINDOW_AUTOSIZE );
cvShowImage("Example Gray", img_gry );
IplImage* img_cny = doCanny( img_gry, 10, 100, 3 );
cvShowImage("Example Canny", img_cny );
cvWaitKey(0);
cvReleaseImage( &img_rgb);
cvReleaseImage( &img_gry);
cvReleaseImage( &img_cny);
cvDestroyWindow("Example Gray");
cvDestroyWindow("Example Canny");
}前面的实现使更加容易进行一些连续的变换
IplImage* doCanny( ··
IplImage* in,
double lowThresh,
double highThresh,
double aperture)
{
if (in->nChannels != 1)
return(0); // Canny only handles gray scale images
IplImage* out = cvCreateImage(
cvGetSize( in ),
in->depth, //IPL_DEPTH_8U,
1);
cvCanny( in, out, lowThresh, highThresh, aperture );
return( out );
};
如下例，可以简单地操作组合。
2、进行两次缩放处理与边缘检测（p29）
IplImage* img_pyr = doPyrDown( img_gry, IPL_GAUSSIAN_5x5 );
IplImage* img_pyr2 = doPyrDown( img_pyr, IPL_GAUSSIAN_5x5 );
IplImage* img_cny = doCanny( img_pyr2, 10, 100, 3 );
...
cvReleaseImage( &img_pyr);
cvReleaseImage( &img_pyr2);
cvReleaseImage( &img_cny);
以下是完整程序：
#include "cv.h"
#include "highgui.h"
IplImage* doCanny(
IplImage* in,
double lowThresh,
double highThresh,
double aperture)
{
IplImage* out = cvCreateImage(
cvGetSize( in ),
in->depth, //IPL_DEPTH_8U,
1);
cvCanny( in, out, lowThresh, highThresh, aperture );
return( out );
};
IplImage* doPyrDown(
IplImage* in,
int filter = IPL_GAUSSIAN_5x5)
{
// Best to make sure input image is divisible by two.
//
assert( in->width%2 == 0 && in->height%2 == 0 );
IplImage* out = cvCreateImage(
cvSize( in->width/2, in->height/2 ),
in->depth,
in->nChannels
);
cvPyrDown( in, out );
return( out );
};
int main( int argc, char** argv )
{
IplImage* img_rgb = cvLoadImage( argv[1] );
IplImage* img_gry = cvCreateImage( cvSize( img_rgb->width,img_rgb->height ), img_rgb->depth, 1);
cvCvtColor(img_rgb, img_gry ,CV_BGR2GRAY);
IplImage* img_pyr = doPyrDown( img_gry, IPL_GAUSSIAN_5x5 );
IplImage* img_pyr2 = doPyrDown( img_pyr, IPL_GAUSSIAN_5x5 );
IplImage* img_cny = doCanny( img_pyr2, 10, 100, 3 );
cvNamedWindow("Example Gray", CV_WINDOW_AUTOSIZE );
cvNamedWindow("Example Pyr", CV_WINDOW_AUTOSIZE );
cvNamedWindow("Example Canny", CV_WINDOW_AUTOSIZE );
cvShowImage("Example Gray", img_gry );
cvShowImage("Example Pyr", img_pyr2 );
cvShowImage("Example Canny", img_cny );
cvWaitKey(0);
cvReleaseImage( &img_rgb);
cvReleaseImage( &img_gry);
cvReleaseImage( &img_pyr);
cvReleaseImage( &img_pyr2);
cvReleaseImage( &img_cny);
cvDestroyWindow("Example Gray");
cvDestroyWindow("Example Pyr");
cvDestroyWindow("Example Canny");
}3、自清理模式（p30）
通过每个独立阶段释放内存来简化上例中图像处理流程：
out = doPyrDown( out );
out = doPyrDown( out );
out = doCanny( out, 10, 100, 3 );
...
cvReleaseImage( &out);
以下是完整程序：
#include "cv.h"
#include "highgui.h"
IplImage* doCanny(
IplImage* in,
double lowThresh,
double highThresh,
double aperture)
{
IplImage* out = cvCreateImage(
cvGetSize( in ),
in->depth, //IPL_DEPTH_8U,
1);
cvCanny( in, out, lowThresh, highThresh, aperture );
return( out );
};
IplImage* doPyrDown(
IplImage* in,
int filter = IPL_GAUSSIAN_5x5)
{
// Best to make sure input image is divisible by two.
//
assert( in->width%2 == 0 && in->height%2 == 0 );
IplImage* out = cvCreateImage(
cvSize( in->width/2, in->height/2 ),
in->depth,
in->nChannels
);
cvPyrDown( in, out );
return( out );
};
int main( int argc, char** argv )
{
cvNamedWindow("Example Gray", CV_WINDOW_AUTOSIZE );
cvNamedWindow("Example Pyr", CV_WINDOW_AUTOSIZE );
cvNamedWindow("Example Canny", CV_WINDOW_AUTOSIZE );
IplImage* img_rgb = cvLoadImage( argv[1] );
IplImage* out;
out = cvCreateImage( cvSize( img_rgb->width,img_rgb->height ), img_rgb->depth, 1);
cvCvtColor(img_rgb, out ,CV_BGR2GRAY);
cvShowImage("Example Gray", out );
out = doPyrDown( out );
out = doPyrDown( out );
cvShowImage("Example Pyr", out );
out = doCanny( out, 10, 100, 3 );
cvShowImage("Example Canny", out );
cvWaitKey(0);
cvReleaseImage( &out);
cvDestroyWindow("Example Gray");
cvDestroyWindow("Example Pyr");
cvDestroyWindow("Example Canny");
}二、打开摄像头
【问题】：用opencv3.0运行打开摄像头的程序时，只显示灰色。并且运行几次后要求选择摄像头，随后闪退。
【原因】：
以下是网络版，2.4.9,3.0运行成功：
#include 以下是书p30的版本，出现闪退情况，待解决：
#include "cv.h"
#include "highgui.h"
int main(int argc, char** argv) {
cvNamedWindow("Example2_9", CV_WINDOW_AUTOSIZE);
CvCapture* capture;
if (argc == 1) {
capture = cvCreateCameraCapture(0);
}
else {
capture = cvCreateFileCapture(argv[1]);
}
assert(capture != NULL);
IplImage* frame;
while (1) {
frame = cvQueryFrame(capture);
if (!frame) break;
cvShowImage("Example2_9", frame);
char c = cvWaitKey(10);
if (c == 27) break;
}
cvReleaseCapture(&capture);
cvDestroyWindow("Example2_9");
}网上的测试程序，3.0无法打开，2.4.9可以：
#include 【问题】：不能显示图像。
【原因】：命令参数里有别的变量忘记删了。
网上的测试程序，显示灰色：
//#include "stdafx.h"
#include 【问题】：#include "stdafx.h"没有这个文件。若注释掉则出现选择摄像机的界面且闪退。
【解决】：注释掉#include "stdafx.h"；
CvCapture* pCapture = cvCreateCameraCapture(-1);不可用
【原因】：
所谓头文件预编译，就是把一个工程(Project)中使用的一些MFC标准头文件(如Windows.H、Afxwin.H)预先编译，以后该工程编译时，不再编译这部分头文件，仅仅使用预编译的结果。这样可以加快编译速度，节省时间。
预编译头文件通过编译stdafx.cpp生成，以工程名命名，由于预编译的头文件的后缀是“pch”，所以编译结果文件是projectname.pch。
编译器通过一个头文件stdafx.h来使用预编译头文件。stdafx.h这个头文件名是可以在project的编译设置里指定的。编译器认为，所有在指令#include “stdafx.h”前的代码都是预编译的，它跳过#include “stdafx. h”指令，使用projectname.pch编译这条指令之后的所有代码。
因此，所有的MFC实现文件第一条语句都是：#include “stdafx.h”。
小结：摄像头打不开，有版本问题，命令参数问题，（可能是stdafx.h问题）。
ps：对于闪退问题，从网上查到的解决方法是：在return语句前面加上system(“pause”);，另外加上头文件include