前言
最近在51Halcon答疑区有找到一个检测实例:在低对比度图像中检测圆形轮廓,这里分享给大家。
问题链接:
https://www.51halcon.com/thread-4876-1-1.html
1. 问题描述
问题提出者想要在如下图片中找到圆形轮廓:
2. OpenCV 实现步骤
主要步骤如下:
- 读取原图并转换为灰度图;
- 提取ROI区域;
- 阈值分割
- 查找轮廓并根据圆形轮廓特征(半径大小,外界矩形长宽比)过滤轮廓
- 绘制圆形轮廓;
3. 源码实现
#include <iostream>
#include <opencv2\imgcodecs.hpp>
#include <opencv2\core.hpp>
#include <opencv2\imgproc.hpp>
#include <opencv2\highgui.hpp>
#include <vector>
using namespace cv;
int main()
{
std::string strImgFile = "C:\\Temp\\common\\Workspace\\Opencv\\images\\BlueROI.jpg";
Mat mSrc = imread(strImgFile);
CV_Assert(!mSrc.empty());
//resize(mSrc, mSrc, Size(mSrc.cols / 2, mSrc.rows / 2));
Mat mGray;
cvtColor(mSrc, mGray, COLOR_BGR2GRAY);
CV_Assert(!mGray.empty());
imshow("gray", mGray);
Mat mRoi;
mGray(Rect(Point(160, 70), Point(160 + 210, 70 + 220))).copyTo(mRoi);
CV_Assert(!mRoi.empty());
imshow("roi", mRoi);
Mat mThresh;
double thresh = threshold(mRoi, mThresh, 30, 255, THRESH_BINARY_INV);
std::cout << "Threshold value:" << thresh << std::endl;
CV_Assert(!mThresh.empty());
imshow("threshold", mThresh);
/*Mat mCircleKernel = getStructuringElement(MORPH_ELLIPSE, Size(3, 3));
Mat mMorph;
morphologyEx(mThresh, mMorph, MORPH_DILATE, mCircleKernel);
CV_Assert(!mMorph.empty());
imshow("morph", mMorph);*/
Mat mSrcCopy = mSrc.clone();
std::vector<std::vector<Point>> contours;
findContours(mThresh, contours, RETR_EXTERNAL, CHAIN_APPROX_NONE);
for (int i = 0; i < contours.size(); i++)
{
Point2f center;
float radius;
minEnclosingCircle(contours[i], center, radius);
RotatedRect rr = minAreaRect(contours[i]);
int max = rr.size.width > rr.size.height ? rr.size.width : rr.size.height;
int min = rr.size.height > rr.size.width ? rr.size.width : rr.size.height;
if (radius > 10 && radius < 50 && max / min < 1.5)
{
//drawContours(mSrcCopy, contours, i, Scalar(0, 0, 255), 1, 8, noArray(), 2000, Point(160, 70));
circle(mSrcCopy, Point(int(center.x + 160), int(center.y + 70)), int(radius-5), Scalar(0, 0, 255));
}
}
imshow("result", mSrcCopy);
waitKey();
destroyAllWindows();
return 0;
}
4. 结果展示
总结
这里的实现比较粗糙,没有准确定位要检测的圆形轮廓,目前没有想到比较好的方法,如果有大神有好的方法,希望不吝赐教,谢谢!