问题描述

我有一个精明的边缘图像

I have a canny edge image

我想删除除看起来像半圆/椭圆或C"的线条之外的所有线条.尝试了 Hough Circle 变换，它检测到所有曲线.不需要那个.

I want to remove all line except the lines that look like a semi-circle/ellipse or a 'C'. Tried Hough Circle transforms, it detects all curves.Don't need that.

推荐答案

一个简单的方法是:

1. 查找连接的组件
2. 找到最小的定向边界框
3. 计算框的纵横比，并检查它是否被拉长.

在你的图片上，我用红色几乎直线标记，用绿色标记曲线.你可以玩纵横比的阈值:

On your image, I marked in red almost straight lines, and in green the curved lines. You can play with the threshold on the aspect ratio:

代码:

#include<opencv2/opencv.hpp>
using namespace cv;


int main()
{
    // Load image
    Mat1b img = imread("path_to_img", IMREAD_GRAYSCALE);

    // Create output image
    Mat3b out;
    cvtColor(img, out, COLOR_GRAY2BGR);

    // Find contours
    vector<vector<Point>> contours;
    findContours(img.clone(), contours, RETR_LIST, CHAIN_APPROX_NONE);

    for (const auto& contour : contours)
    {
        // Find minimum area rectangle
        RotatedRect rr = minAreaRect(contour);

        // Compute aspect ratio
        float aspect_ratio = min(rr.size.width, rr.size.height) / max(rr.size.width, rr.size.height);

        // Define a threshold on the aspect ratio in [0, 1]
        float thresh = 0.2f;

        Vec3b color;
        if (aspect_ratio < thresh) { 
            // Almost straight line
            color = Vec3b(0,0,255); // RED
        }
        else {
            // Curved line
            color = Vec3b(0, 255, 0); // GREEN
        }

        // Color output image
        for (const auto& pt : contour) {
            out(pt) = color;
        }
    }

    imshow("Out", out);
    waitKey();

    return 0;
}

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