OpenCV学习06

导出边缘检测后的图像

//
//  main.cpp
//  Study06
//
//  Created by Sean on 16/2/21.
//  Copyright © 2016年 Sean. All rights reserved.
//

#include <iostream>
#include "highgui.h"
#include "cv.h"

using namespace std;

IplImage* doCanny(IplImage* in, double lowThresh, double highThresh, double aperture)
{
    if(in->nChannels!=1)
        return(0);
    IplImage* out = cvCreateImage(cvSize(in->width,in->height), IPL_DEPTH_8U, 1);
    //IplImage* out = cvCreateImage(cvGetSize(in), IPL_DEPTH_8U, 1);
    cvCanny(in, out, lowThresh, highThresh, aperture);
    return out;
}

int main(int argc, const char * argv[]) {
    // insert code here...
    cout << "Hello, World!\n";
    IplImage* in = cvLoadImage("/Users/sean/Pictures/11.png");
    IplImage* in2 = cvCreateImage(cvGetSize(in), IPL_DEPTH_8U, 1);
    cvCvtColor(in,in2,CV_BGR2GRAY);
    char A[]="in_re",B[]="in_af",C[]="out";
    cvNamedWindow(A);
    cvNamedWindow(B);
    cvNamedWindow(C);
    cvShowImage(A, in);
    cvShowImage(B, in2);
    cvShowImage(C, doCanny(in2, 50, 200, 3));
    while(cvWaitKey(0)!=27);
    cvReleaseImage(&in);
    cvDestroyAllWindows();
    return 0;
}

这里发现个问题，就是cvCanny的作用对象必须是单通道的图像结构，(普及知识：OpenCV中所有的数据结构都是以结构体的形式实现，并以结构体指针的形式传递。这就能解释为什么每次申请图像空间的时候是“IplImage* img;”了)，也就是说，图像结构体中的nChannels必须为1才能准确的实行阈值边缘检测，虽然在nChannels为3的时候（色彩的三个通道）也能用cvCanny，但所得的两个结果有所不同。下面给出nChannels为3的时候的代码：

//
//  main.cpp
//  Study06
//
//  Created by Sean on 16/2/21.
//  Copyright © 2016年 Sean. All rights reserved.
//

#include <iostream>
#include "highgui.h"
#include "cv.h"

using namespace std;

IplImage* doCanny(IplImage* in, double lowThresh, double highThresh, double aperture)
{
//    if(in->nChannels!=1)
//        return(0);
    IplImage* out = cvCreateImage(cvSize(in->width,in->height), IPL_DEPTH_8U, 1);
    //IplImage* out = cvCreateImage(cvGetSize(in), IPL_DEPTH_8U, 1);
    cvCanny(in, out, lowThresh, highThresh, aperture);
    return out;
}

int main(int argc, const char * argv[]) {
    // insert code here...
    cout << "Hello, World!\n";
    IplImage* in = cvLoadImage("/Users/sean/Pictures/11.png");
    IplImage* in2 = cvCreateImage(cvGetSize(in), IPL_DEPTH_8U, 1);
    cvCvtColor(in,in2,CV_BGR2GRAY);
    char A[]="in_re",B[]="in_af",C[]="out_1",D[]="out_3";
    cvNamedWindow(A);
    cvNamedWindow(B);
    cvNamedWindow(C);
    cvNamedWindow(D);
    cvShowImage(A, in);
    cvShowImage(B, in2);
    cvShowImage(C, doCanny(in2, 50, 200, 3));
    cvShowImage(D, doCanny(in, 50, 200, 3));
    while(cvWaitKey(0)!=27);
    cvReleaseImage(&in);
    cvDestroyAllWindows();
    return 0;
}