opencv3/C++輪廓的提取與篩選方式

2020-01-26 13:22:45

字體：大中小

來源：轉載

供稿：網友

輪廓提取

findContours發現輪廓

findContours(InputOutputArray binImg, //輸入8bit圖像，0值像素值不變，非0的像素看成1；（變為二值圖像） OutputArrayOfArrays contours,//輸出找到的輪廓對象OutputArray, hierachy// 圖像的拓撲結構int mode, //輪廓返回的模式(RETR_TREE等)int method,//發現方法(CHAIN_APPROX_SIMPLE等)Point offset=Point()//輪廓像素的位移（默認沒有位移（0, 0））)

【報錯問題】

findContours()有時會報告“已觸發了一個斷點”等錯誤，嘗試過y有效的解決方法有：

1.為vector提前申請一定的空間，如

std::vector<std::vector<Point>> contours(500)

2.Debug版切換為Release版；

drawContours繪制輪廓

drawContours(InputOutputArray binImg, // 輸出圖像 OutputArrayOfArrays contours,//找到的全部輪廓對象Int contourIdx//輪廓索引號const Scalar & color,//繪制顏色int thickness,//繪制線寬int lineType ,//線的類型（默認8）InputArray hierarchy,//拓撲結構圖int maxlevel,//最大層數（0只繪制當前的，1表示繪制繪制當前及其內嵌的輪廓）Point offset=Point()//輪廓位移)

示例：

#include<opencv2/opencv.hpp>using namespace cv;int main(){ Mat src,dst; src = imread("E:/image/image/shape.jpg"); if(src.empty()) { printf("can not load image /n"); return -1; } namedWindow("input", CV_WINDOW_AUTOSIZE); imshow("input", src); dst = Mat::zeros(src.size(), CV_8UC3); blur(src,src,Size(3,3)); cvtColor(src,src,COLOR_BGR2GRAY); Canny(src, src, 20, 80, 3, false); std::vector<std::vector<Point>> contours; std::vector<Vec4i> hierarchy; findContours(src, contours, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0)); RNG rng(0); for(int i = 0; i < contours.size(); i++) { Scalar color = Scalar(rng.uniform(0,255), rng.uniform(0,255), rng.uniform(0,255)); drawContours(dst, contours, i, color, 2, 8, hierarchy, 0, Point(0,0)); } namedWindow("output", CV_WINDOW_AUTOSIZE); imshow("output",dst); waitKey(); return 0;}

使用opencv3時(測試用opencv3.1.0)發現，cv命名空間下沒有了vector，而在opencv2中(測試用opencv2.4.10)還存在。后查看各自的頭文件發現：

opencv.hpp頭文件中包含著core.hpp（#include “opencv2/core.hpp”）;

而在opencv2的core.hpp中包含有

........#include <map>#include <new>#include <string>#include <vector>.......

等頭文件，但在opencv3的core.hpp中刪去這些包含項。

因此在使用opencv3時cv命名空間下沒有了vector。

使用opencv2.4.10時可以寫：

#include<opencv2/opencv.hpp>using namespace cv;int main(){ Mat src,dst; src = imread("E:/image/image/shape.jpg"); if(src.empty()) { printf("can not load image /n"); return -1; } namedWindow("input", CV_WINDOW_AUTOSIZE); imshow("input", src); dst = Mat::zeros(src.size(), CV_8UC3); blur(src,src,Size(5,5)); Canny(src, src, 20, 80, 3, false); vector<vector<Point>>contours; vector<Vec4i> hierarchy; findContours(src, contours, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0)); RNG rng(0); for(int i = 0; i < contours.size(); i++) { Scalar color = Scalar(rng.uniform(0,255), rng.uniform(0,255), rng.uniform(0,255)); drawContours(dst, contours, i, color, 2, 8, hierarchy, 0, Point(0,0)); } namedWindow("output", CV_WINDOW_AUTOSIZE); imshow("output",dst); waitKey(); return 0;}

繪制輪廓外矩形框

常用繪制輪廓外形狀的函數：

cv::boundingRect(InputArray points)繪制一個矩形（輪廓周圍最小矩形左上角點和右下角點）

cv::minAreaRect(InputArray points)繪制輪廓周圍最小旋轉矩形

cv::minEnclosingCircle(InputArray points, Point2f& center, float& radius)//繪制輪廓周圍最小圓形

cv::fitEllipse(InputArray points)繪制輪廓周圍最小橢圓

繪制輪廓外矩形框：

#include<opencv2/opencv.hpp>using namespace cv;int main(){ Mat src,dst; src = imread("E:/image/shape.jpg"); if(src.empty()) { printf("can not load image /n"); return -1; } namedWindow("input", CV_WINDOW_AUTOSIZE); imshow("input", src); dst = Mat::zeros(src.size(), CV_8UC3); std::vector<std::vector<Point>>contours; std::vector<Vec4i> hierarchy; blur(src,src,Size(3,3)); cvtColor(src,src,COLOR_BGR2GRAY); Canny(src, src, 20, 80, 3, false); findContours(src, contours, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0)); RNG rng(0); std::vector<std::vector<Point>> contoursPloy(contours.size()); std::vector<RotatedRect> minRects(contours.size()); for(int i = 0; i < contours.size(); i++) { minRects[i] = minAreaRect(Mat(contours[i])); Scalar color = Scalar(rng.uniform(0,255), rng.uniform(0,255), rng.uniform(0,255)); drawContours(dst, contoursPloy, i, color, 1,8,std::vector<Vec4i>(), 0, Point(0, 0)); Point2f rectPoints[4]; minRects[i].points(rectPoints); for (int j = 0; j < 4; j++) {  line(dst, rectPoints[j], rectPoints[(j+1)%4], color, 1, 8, 0); } } namedWindow("output", CV_WINDOW_AUTOSIZE); imshow("output",dst); waitKey(); return 0;}

輪廓篩選

moments(InputArray array,//輸入數據bool  binaryImage=false //是否為二值圖像)contourArea(InputArray contour,//輸入輪廓數據bool  oriented//返回絕對值（默認false）)arcLength(InputArray curve,//輸入輪廓bool  closed// 輪廓否是封閉曲線)

輪廓篩選示例：

使用輪廓的面積和長度特征對輪廓進行篩選后用外接矩形將篩選后的輪廓框選出來。

#include<opencv2/opencv.hpp>using namespace cv;void trackBar(int,void*);Mat src,dst;std::vector<std::vector<Point>>contours;int area = 0, length = 0;int main(){ src = imread("E:/image/shape.jpg"); if(src.empty()) { printf("can not load image /n"); return -1; } namedWindow("input", CV_WINDOW_AUTOSIZE); imshow("input", src); dst = Mat::zeros(src.size(), CV_8UC3); std::vector<Vec4i> hierarchy; blur(src,dst,Size(3,3)); cvtColor(dst,dst,COLOR_BGR2GRAY); Canny(dst, dst, 20, 80, 3, false); findContours(dst, contours, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0)); namedWindow("output", CV_WINDOW_AUTOSIZE); createTrackbar("area:", "output", &area,150,trackBar); createTrackbar("length:", "output", &length,150,trackBar); waitKey(); return 0;}void trackBar(int,void*){ Mat src1 = src.clone(); RNG rng(0); std::vector<std::vector<Point>> contoursPloy(contours.size()); std::vector<RotatedRect> minRects(contours.size()); for(int i = 0; i < contours.size(); i++) { if(contourArea(contours[i]) > area && arcLength(contours[i], false) > length) {  minRects[i] = minAreaRect(Mat(contours[i]));  Scalar color = Scalar(rng.uniform(0,255), rng.uniform(0,255), rng.uniform(0,255));  //drawContours(dst, contoursPloy, i, color, 1,8,vector<Vec4i>(), 0, Point(0, 0));  Point2f rectPoints[4];  minRects[i].points(rectPoints);  for (int j = 0; j < 4; j++)  {  line(src1, rectPoints[j], rectPoints[(j+1)%4], color, 2, 8, 0);  } } } imshow("output",src1); src1 = src;}