OpenCV 无法设置 SVM 参数

Question

我刚刚开始使用 C++ OpenCV 学习 SVM，并参考了 SVM 文档 here。我想尝试 link 中的示例源代码以先熟悉它，但我无法运行示例源代码。它 returns 错误：

Error 1 error C2065: 'CvSVMParams' : undeclared identifier

我正在使用 Visual Studio 2012 和 OpenCV 3.0.0。设置过程应该是正确的，因为除此之外所有其他代码都运行良好。

Answer 1

很多事情都变了from OpenCV 2.4 to OpenCV 3.0。其中，机器学习模块不向后兼容。

这是 OpenCV tutorial code for the SVM，OpenCV 3.0 更新：

#include <opencv2/core.hpp>
#include <opencv2/imgproc.hpp>
#include "opencv2/imgcodecs.hpp"
#include <opencv2/highgui.hpp>
#include <opencv2/ml.hpp>

using namespace cv;
using namespace cv::ml;

int main(int, char**)
{
    // Data for visual representation
    int width = 512, height = 512;
    Mat image = Mat::zeros(height, width, CV_8UC3);

    // Set up training data
    int labels[4] = { 1, -1, -1, -1 };
    Mat labelsMat(4, 1, CV_32SC1, labels);

    float trainingData[4][2] = { { 501, 10 }, { 255, 10 }, { 501, 255 }, { 10, 501 } };
    Mat trainingDataMat(4, 2, CV_32FC1, trainingData);

    // Set up SVM's parameters
    Ptr<SVM> svm = SVM::create();
    svm->setType(SVM::C_SVC);
    svm->setKernel(SVM::LINEAR);
    svm->setTermCriteria(TermCriteria(TermCriteria::MAX_ITER, 100, 1e-6));

    // Train the SVM with given parameters
    Ptr<TrainData> td = TrainData::create(trainingDataMat, ROW_SAMPLE, labelsMat);
    svm->train(td);

    // Or train the SVM with optimal parameters
    //svm->trainAuto(td);

    Vec3b green(0, 255, 0), blue(255, 0, 0);
    // Show the decision regions given by the SVM
    for (int i = 0; i < image.rows; ++i)
        for (int j = 0; j < image.cols; ++j)
        {
            Mat sampleMat = (Mat_<float>(1, 2) << j, i);
            float response = svm->predict(sampleMat);

            if (response == 1)
                image.at<Vec3b>(i, j) = green;
            else if (response == -1)
                image.at<Vec3b>(i, j) = blue;
        }

    // Show the training data
    int thickness = -1;
    int lineType = 8;
    circle(image, Point(501, 10), 5, Scalar(0, 0, 0), thickness, lineType);
    circle(image, Point(255, 10), 5, Scalar(255, 255, 255), thickness, lineType);
    circle(image, Point(501, 255), 5, Scalar(255, 255, 255), thickness, lineType);
    circle(image, Point(10, 501), 5, Scalar(255, 255, 255), thickness, lineType);

    // Show support vectors
    thickness = 2;
    lineType = 8;
    Mat sv = svm->getSupportVectors();

    for (int i = 0; i < sv.rows; ++i)
    {
        const float* v = sv.ptr<float>(i);
        circle(image, Point((int)v[0], (int)v[1]), 6, Scalar(128, 128, 128), thickness, lineType);
    }

    imwrite("result.png", image);        // save the image

    imshow("SVM Simple Example", image); // show it to the user
    waitKey(0);

}

输出应如下所示：

Answer 2

我发现上面的代码有效，但我需要做一点小修改以将标签转换为整数。修改以粗体显示：

// Set up training data **Original**:

int labels[4] = { 1, -1, -1, -1 };

Mat labelsMat(4, 1, **CV_32SC1**, labels);

// Set up training data **Modified**:

int labels[4] = { 1, -1, -1, -1 };

Mat labelsMat(4, 1, **CV_32S**, labels);

OpenCV 无法设置 SVM 参数

OpenCV unable to set up SVM Parameters

c++

opencv

svm

visual-studio-2012

opencv3.0