OpenCV之图像处理case(二) 直线检测

代码

#include "../common/common.hpp"

static int max_count = 255;
static int threshold_value = 100;
static const char* title = "Hough Lines";
static Mat src, roiImage, dst;

static void detectLines(int, void*);
static void morphologyLines(int, void*);

void main(int argc, char ** argv)
{
    src = imread(getCVImagesPath("images/case3-2.png"), IMREAD_GRAYSCALE);
    imshow("src3-2", src);
    Rect roi = Rect(10, 10, src.cols - 20, src.rows - 20);
    roiImage = src(roi); // 周边白线裁剪掉

    //namedWindow(title, CV_WINDOW_AUTOSIZE);
    //createTrackbar("Threshold:", title, &threshold_value, max_count, detectLines);
    //detectLines(0, 0);

    morphologyLines(0, 0);

    waitKey(0);
}

void detectLines(int, void*) // 单纯的使用霍夫直线检测，得不到想要的结果
{
    Canny(roiImage, dst, threshold_value, threshold_value * 2, 3, false);
    //threshold(roiImage, dst, 0, 255, THRESH_BINARY | THRESH_OTSU); // 二值化
    vector<Vec4i> lines; // 保存检测到的直线，Vec4i 保存线段两个点的四个坐标值
    HoughLinesP(dst, lines, 1, CV_PI / 180.0, 30, 30.0, 0);
    cout << "lines.size=" << lines.size() << endl;
    cvtColor(dst, dst, COLOR_GRAY2BGR);
    for (size_t t = 0; t < lines.size(); t++) {
        Vec4i ln = lines[t];
        line(dst, Point(ln[0], ln[1]), Point(ln[2], ln[3]), Scalar(0, 0, 255), 2, 8, 0);
    }
    imshow(title, dst);
}

void morphologyLines(int, void*) // 通过图像形态学操作来寻找直线，霍夫获取位置信息与显示
{
    // binary image
    Mat binaryImage, morhpImage;
    threshold(roiImage, binaryImage, 0, 255, THRESH_BINARY_INV | THRESH_OTSU); // 二值化
    imshow("binary", binaryImage);

    // morphology operation
    Mat kernel = getStructuringElement(MORPH_RECT, Size(30, 1), Point(-1, -1)); // 结构元素的选取非常重要
    morphologyEx(binaryImage, morhpImage, MORPH_OPEN, kernel, Point(-1, -1)); // 开操作
    imshow("morphology result", morhpImage); // 如果觉得此图的效果不够明显，可以膨胀一下此图，不膨胀对最终结果无影响

    // dilate image
    kernel = getStructuringElement(MORPH_RECT, Size(3, 3), Point(-1, -1));
    dilate(morhpImage, morhpImage, kernel); // 膨胀，让二值图的直线更明显
    imshow("morphology lines", morhpImage);

    // hough lines
    vector<Vec4i> lines; // 保存检测到的直线，Vec4i 保存线段两个点的四个坐标值
    HoughLinesP(morhpImage, lines, 1, CV_PI / 180.0, 30, 20.0, 0);
    cout << "mor lines.size=" << lines.size() << endl; // mor lines.size=32
    Mat resultImage = roiImage.clone();
    cvtColor(resultImage, resultImage, COLOR_GRAY2BGR);
    for (size_t t = 0; t < lines.size(); t++) {
        Vec4i ln = lines[t];
        line(resultImage, Point(ln[0], ln[1]), Point(ln[2], ln[3]), Scalar(0, 0, 255), 2, 8, 0);
    }
    imshow("final img", resultImage);
}

效果图