c++ - OpenCV中的分段错误
问题描述
我最近开始使用 C++ 做一些图像处理的东西,并面临分割错误的问题。希望有人能帮我弄清楚发生了什么?谢谢!!问题是下面附加的代码可以正常工作,但是如果我的“vector roi_corners(4);”的声明 改为“vector roi_corners;” 然后使用“push_back()”和“clear()”更新向量,它会得到分段错误。谁能帮我澄清这个问题的原因?谢谢!!
OpenCV 版本:4.4.0
MacOS版本:10.14.5
可行的代码
#include <opencv2/opencv.hpp>
#include <iostream>
#include <math.h>
#include <vector>
#define PI 3.14159265
#define WINDOW "Image Correction"
using namespace std;
using namespace cv;
vector< Point2f> roi_corners(4);
vector< Point2f> dst_corners(4);
Mat img1;
Mat cache;
int roi_id;
void On_mouse(int event, int x, int y, int flags, void*);
int main(int argc, char const *argv[])
{
//import image
roi_id = 0;
img1 = imread("Board.jpg");
if ( img1.empty() )
{
cerr << "Please Import an Image!!" << endl;
}
int factor = 60;//for pixel adjustment
cache = img1.clone();//copy for retake points
imshow(WINDOW, img1);
/*Run the point taking procedure*/
while(true){
setMouseCallback(WINDOW, On_mouse, 0);
char c = (char)waitKey( 10 );
if(c=='n') break;//press 'n' when determine the four point you want
if(c=='e') {roi_id=0; img1 = cache.clone();} //press 'e' to retake the foru point
}
/*For adjustment point estimation*/
dst_corners[0].x = roi_corners[0].x;
dst_corners[0].y = roi_corners[0].y;
dst_corners[1].x = roi_corners[0].x+factor*1;
dst_corners[1].y = roi_corners[0].y;
dst_corners[2].x = roi_corners[0].x+factor*1;
dst_corners[2].y = roi_corners[0].y+factor*1;
dst_corners[3].x = roi_corners[0].x;
dst_corners[3].y = roi_corners[0].y+factor*1;
Mat M = getPerspectiveTransform(roi_corners, dst_corners);
Mat warped_image;
/*Print the corrected picture*/
Size sz = cache.size();
warpPerspective(cache, warped_image, M, Size(sz.width, sz.height)); // do perspective transformation
imshow("Corrected Image", warped_image);
waitKey(0);
cout<<"complete"<<endl;
return 0;
}
void On_mouse(int event, int x, int y, int flags, void*)
{ imshow(WINDOW, img1);
if(roi_id<4){
if (event == EVENT_LBUTTONDOWN){
roi_corners[roi_id].x=x;
roi_corners[roi_id].y=y;
cout<<"The Point You Take is: "<<x<<' '<<y<<endl;
roi_id++;
circle(img1, Point(x,y), 2, Scalar(0, 0, 255), LINE_8 ,0);
imshow(WINDOW, img1);
}
}
}
如果我这样修改代码,它将显示段错误
#include <opencv2/opencv.hpp>
#include <iostream>
#include <math.h>
#include <vector>
#define PI 3.14159265
#define WINDOW "Image Correction"
using namespace std;
using namespace cv;
vector< Point2f> roi_corners;
vector< Point2f> dst_corners;
Mat img1;
Mat cache;
void On_mouse(int event, int x, int y, int flags, void*);
int main(int argc, char const *argv[])
{
//import image
roi_id = 0;
img1 = imread("Board.jpg");
if ( img1.empty() )
{
cerr << "Please Import an Image!!" << endl;
}
int factor = 60;//for pixel adjustment
cache = img1.clone();//copy for retake points
imshow(WINDOW, img1);
/*Run the point taking procedure*/
while(true){
setMouseCallback(WINDOW, On_mouse, 0);
char c = (char)waitKey( 10 );
if(c=='n') break;//press 'n' when determine the four point you want
if(c=='e') {roi_corner.clear(); img1 = cache.clone();} //press 'e' to retake the foru point
}
/*For adjustment point estimation*/
dst_corners[0].x = roi_corners[0].x;
dst_corners[0].y = roi_corners[0].y;
dst_corners[1].x = roi_corners[0].x+factor*1;
dst_corners[1].y = roi_corners[0].y;
dst_corners[2].x = roi_corners[0].x+factor*1;
dst_corners[2].y = roi_corners[0].y+factor*1;
dst_corners[3].x = roi_corners[0].x;
dst_corners[3].y = roi_corners[0].y+factor*1;
Mat M = getPerspectiveTransform(roi_corners, dst_corners);
Mat warped_image;
/*Print the corrected picture*/
Size sz = cache.size();
warpPerspective(cache, warped_image, M, Size(sz.width, sz.height)); // do perspective transformation
imshow("Corrected Image", warped_image);
waitKey(0);
cout<<"complete"<<endl;
return 0;
}
void On_mouse(int event, int x, int y, int flags, void*)
{ imshow(WINDOW, img1);
if(roi_corners.size()<4){
if (event == EVENT_LBUTTONDOWN){
roi_corners.push_back(Point2f(x,y));
cout<<"The Point You Take is: "<<x<<' '<<y<<endl;
circle(img1, Point(x,y), 2, Scalar(0, 0, 255), LINE_8 ,0);
imshow(WINDOW, img1);
}
}
}
解决方案
您的代码有几件事。您声明了一个包含 4 个元素的向量,但不对其进行初始化。根据您的平台和数据类型,您可能会看到不良行为。尝试在同一行声明和初始化你的向量:
std::vector<cv::Point2f> roi_corners( 4, cv::Point2f(0.0, 0.0) );
当然,如果您使用初始容量 ( size
) 和初始值声明向量,您可以使用 索引每个元素std::vector<>::operator[]
:
roi_corners[0] = cv::Point2f( 1.0, 2.0 );
roi_corners[1] = cv::Point2f( 3.0, 4.0 );
roi_corners[2] = cv::Point2f( 5.0, 6.0 );
roi_corners[3] = cv::Point2f( 7.0, 8.0 );
通过使用初始大小声明向量,您已经分配了将用于store
和load
向量的各个元素的内存。现在,假设您没有使用初始大小声明向量并使用它push_back
随时添加元素:
//vector declaration with no initial size:
std::vector<cv::Point2f> roi_corners;
//store a new element into the vector:
roi_corners.push_back( cv::Point2f(1.0, 2.0) );
很酷,您的向量已经存储了一个新元素,并且只显示了一个项目的容量。但是,您仍然这样做:
roi_corners[0] = cv::Point2f( 1.0, 2.0 ); // data overwrite in position 0
roi_corners[1] = cv::Point2f( 3.0, 4.0 ); // you haven't allocated memory for this yet!
Result: seg fault
推论:如果你有一个预定义的 size 向量,你可以从viaN
索引元素,因为已经分配了内存来保存所有元素。如果您尝试处理超出此范围的元素,您将收到一个.0
N
std::vector<>::operator[]
N
seg fault
推荐阅读
- python-3.x - 如何在 PonyORM 中“LEFT JOIN”的“ON”原因中添加条件
- apache-spark - 获取特征重要性 PySpark 朴素贝叶斯分类器
- c# - 如何格式化导出到 Excel 的 DataGridView 的背景?
- java - Is it a good idea to use datastax mapper to save thousands of records using saveAsync
- java - selenium webdriver没有使用apache poi将数据写入excel表
- c# - 如何为构造函数包含 HttpClient 和一些字符串的类设置一些 .NET Core 依赖注入?
- android - spown cmd enoent error while creating react native app
- google-cloud-platform - Turning off Windows Update on Google Cloud Platform Windows Virtual Machine (Server 2016)
- makefile - 如何在使用 make 规则的变量提供先决条件的同时处理文件名中的空格?
- react-native - axios 和 android 模拟器的网络错误