OpenCV 3.3中給出了支持向量機(Support Vector Machines)的實現(xiàn)，即cv::ml::SVM類，此類的聲明在include/opencv2/ml.hpp文件中，實現(xiàn)在modules/ml/src/svm.cpp文件中，它既支持兩分類，也支持多分類，還支持回歸等，OpenCV中SVM的實現(xiàn)源自libsvm庫。其中：

(1)、cv::ml::SVM類：繼承自cv::ml::StateModel，而cv::ml::StateModel又繼承自cv::Algorithm;

(2)、create函數(shù)：為static，new一個SVMImpl用來創(chuàng)建一個SVM對象；

(3)、setType/getType函數(shù)：設(shè)置/獲取SVM公式類型，包括C_SVC、NU_SVC、ONE_CLASS、EPS_SVR、NU_SVR，用于指定分類、回歸等，默認為C_SVC；

(4)、setGamma/getGamma函數(shù)：設(shè)置/獲取核函數(shù)的γ參數(shù)，默認值為1；

(5)、setCoef0/getCoef0函數(shù)：設(shè)置/獲取核函數(shù)的coef0參數(shù)，默認值為0；

(6)、setDegree/getDegree函數(shù)：設(shè)置/獲取核函數(shù)的degreee參數(shù)，默認值為0；

(7)、setC/getC函數(shù)：設(shè)置/獲取SVM優(yōu)化問題的C參數(shù)，默認值為0；

(8)、setNu/getNu函數(shù)：設(shè)置/獲取SVM優(yōu)化問題的υ參數(shù)，默認值為0；

(9)、setP/getP函數(shù)：設(shè)置/獲取SVM優(yōu)化問題的ε參數(shù)，默認值為0；

(10)、setClassWeights/getClassWeights函數(shù)：應(yīng)用在SVM::C_SVC,設(shè)置/獲取weights，默認值是空cv::Mat；

(11)、setTermCriteria/getTermCriteria函數(shù)：設(shè)置/獲取SVM訓(xùn)練時迭代終止條件，默認值是cv::TermCriteria(cv::TermCriteria::MAX_ITER + TermCriteria::EPS,1000, FLT_EPSILON)；

(12)、setKernel/getKernelType函數(shù)：設(shè)置/獲取SVM核函數(shù)類型，包括CUSTOM、LINEAR、POLY、RBF、SIGMOID、CHI2、INTER，默認值為RBF；

(13)、setCustomKernel函數(shù)：初始化CUSTOM核函數(shù)；

(14)、trainAuto函數(shù)：用最優(yōu)參數(shù)訓(xùn)練SVM；

(15)、getSupportVectors/getUncompressedSupportVectors函數(shù)：獲取所有的支持向量；

(16)、getDecisionFunction函數(shù)：決策函數(shù)；

(17)、getDefaultGrid/getDefaultGridPtr函數(shù)：生成SVM參數(shù)網(wǎng)格；

(18)、save/load函數(shù)：保存/載入已訓(xùn)練好的model，支持xml,yaml,json格式；

(19)、train/predict函數(shù)：用于訓(xùn)練/預(yù)測，均使用基類StatModel中的。

關(guān)于支持向量機的基礎(chǔ)介紹可以參考： ?http://blog.csdn.net/fengbingchun/article/details/78326704?

以下是測試代碼，包括train和predict：

#include "opencv.hpp"
#include <string>
#include <vector>
#include <memory>
#include <opencv2/opencv.hpp>
#include <opencv2/ml.hpp>
#include "common.hpp"/// Support Vector Machines ///
int test_opencv_svm_train()
{// two class classifcationconst std::vector<int> labels { 1, -1, -1, -1 };const std::vector<std::vector<float>> trainingData{ { 501, 10 }, { 255, 10 }, { 501, 255 }, { 10, 501 } };const int feature_length{ 2 };const int samples_count{ (int)trainingData.size()};CHECK(labels.size() == trainingData.size());std::vector<float> data(samples_count * feature_length, 0.f);for (int i = 0; i < samples_count; ++i) {for (int j = 0; j < feature_length; ++j) {data[i*feature_length + j] = trainingData[i][j];}}cv::Mat trainingDataMat(samples_count, feature_length, CV_32FC1, data.data());cv::Mat labelsMat((int)samples_count, 1, CV_32SC1, (int*)labels.data());cv::Ptr<cv::ml::SVM> svm = cv::ml::SVM::create();svm->setType(cv::ml::SVM::C_SVC);svm->setKernel(cv::ml::SVM::LINEAR);svm->setTermCriteria(cv::TermCriteria(cv::TermCriteria::MAX_ITER, 100, 1e-6));CHECK(svm->train(trainingDataMat, cv::ml::ROW_SAMPLE, labelsMat));const std::string save_file{ "E:/GitCode/NN_Test/data/svm_model.xml" }; // .xml, .yaml, .jsonssvm->save(save_file);return 0;
}int test_opencv_svm_predict()
{const std::string model_file { "E:/GitCode/NN_Test/data/svm_model.xml" };const std::vector<int> labels{ 1, 1, 1, 1, -1, -1, -1, -1 };const std::vector<std::vector<float>> predictData{ { 490.f, 15.f }, { 480.f, 30.f }, { 511.f, 40.f }, { 473.f, 50.f },{ 2.f, 490.f }, { 100.f, 200.f }, { 247.f, 223.f }, {510.f, 400.f} };const int feature_length{ 2 };const int predict_count{ (int)predictData.size() };CHECK(labels.size() == predictData.size());cv::Ptr<cv::ml::SVM> svm = cv::ml::SVM::load(model_file);for (int i = 0; i < predict_count; ++i) {cv::Mat prdictMat = (cv::Mat_<float>(1, 2) << predictData[i][0], predictData[i][1]);float response = svm->predict(prdictMat);fprintf(stdout, "actual class: %d, target calss: %f\n", labels[i], response);}return 0;
}int test_opencv_svm_simple()
{// two class classifcation// reference: opencv-3.3.0/samples/cpp/tutorial_code/ml/introduction_to_svm/introduction_to_svm.cppconst int width{ 512 }, height{ 512 };cv::Mat image = cv::Mat::zeros(height, width, CV_8UC3);const int labels[] { 1, -1, -1, -1 };const float trainingData[][2] {{ 501, 10 }, { 255, 10 }, { 501, 255 }, { 10, 501 } };cv::Mat trainingDataMat(4, 2, CV_32FC1, (float*)trainingData);cv::Mat labelsMat(4, 1, CV_32SC1, (int*)labels);cv::Ptr<cv::ml::SVM> svm = cv::ml::SVM::create();svm->setType(cv::ml::SVM::C_SVC);svm->setKernel(cv::ml::SVM::LINEAR);svm->setTermCriteria(cv::TermCriteria(cv::TermCriteria::MAX_ITER, 100, 1e-6));svm->train(trainingDataMat, cv::ml::ROW_SAMPLE, labelsMat);// Show the decision regions given by the SVMcv::Vec3b green(0, 255, 0), blue(255, 0, 0);for (int i = 0; i < image.rows; ++i) {for (int j = 0; j < image.cols; ++j) {cv::Mat sampleMat = (cv::Mat_<float>(1, 2) << j, i);float response = svm->predict(sampleMat);if (response == 1)image.at<cv::Vec3b>(i, j) = green;else if (response == -1)image.at<cv::Vec3b>(i, j) = blue;}}// Show the training dataint thickness{ -1 };int lineType{ 8 };cv::circle(image, cv::Point(501, 10), 5, cv::Scalar(0, 0, 0), thickness, lineType);cv::circle(image, cv::Point(255, 10), 5, cv::Scalar(255, 255, 255), thickness, lineType);cv::circle(image, cv::Point(501, 255), 5, cv::Scalar(255, 255, 255), thickness, lineType);cv::circle(image, cv::Point(10, 501), 5, cv::Scalar(255, 255, 255), thickness, lineType);// Show support vectorsthickness = 2;lineType = 8;cv::Mat sv = svm->getUncompressedSupportVectors();for (int i = 0; i < sv.rows; ++i) {const float* v = sv.ptr<float>(i);cv::circle(image, cv::Point((int)v[0], (int)v[1]), 6, cv::Scalar(128, 128, 128), thickness, lineType);}cv::imwrite("E:/GitCode/NN_Test/data/result_svm_simple.png", image);imshow("SVM Simple Example", image);cv::waitKey(0);return 0;
}int test_opencv_svm_non_linear()
{// two class classifcation// reference: opencv-3.3.0/samples/cpp/tutorial_code/ml/non_linear_svms/non_linear_svms.cppconst int NTRAINING_SAMPLES{ 100 }; // Number of training samples per classconst float FRAC_LINEAR_SEP{ 0.9f }; // Fraction of samples which compose the linear separable part// Data for visual representationconst int WIDTH{ 512 }, HEIGHT{ 512 };cv::Mat I = cv::Mat::zeros(HEIGHT, WIDTH, CV_8UC3);// Set up training data randomlycv::Mat trainData(2 * NTRAINING_SAMPLES, 2, CV_32FC1);cv::Mat labels(2 * NTRAINING_SAMPLES, 1, CV_32SC1);cv::RNG rng(100); // Random value generation class// Set up the linearly separable part of the training dataint nLinearSamples = (int)(FRAC_LINEAR_SEP * NTRAINING_SAMPLES);// Generate random points for the class 1cv::Mat trainClass = trainData.rowRange(0, nLinearSamples);// The x coordinate of the points is in [0, 0.4)cv::Mat c = trainClass.colRange(0, 1);rng.fill(c, cv::RNG::UNIFORM, cv::Scalar(1), cv::Scalar(0.4 * WIDTH));// The y coordinate of the points is in [0, 1)c = trainClass.colRange(1, 2);rng.fill(c, cv::RNG::UNIFORM, cv::Scalar(1), cv::Scalar(HEIGHT));// Generate random points for the class 2trainClass = trainData.rowRange(2 * NTRAINING_SAMPLES - nLinearSamples, 2 * NTRAINING_SAMPLES);// The x coordinate of the points is in [0.6, 1]c = trainClass.colRange(0, 1);rng.fill(c, cv::RNG::UNIFORM, cv::Scalar(0.6*WIDTH), cv::Scalar(WIDTH));// The y coordinate of the points is in [0, 1)c = trainClass.colRange(1, 2);rng.fill(c, cv::RNG::UNIFORM, cv::Scalar(1), cv::Scalar(HEIGHT));// Set up the labels for the classeslabels.rowRange(0, NTRAINING_SAMPLES).setTo(1); // Class 1labels.rowRange(NTRAINING_SAMPLES, 2 * NTRAINING_SAMPLES).setTo(2); // Class 2// Train the svmstd::cout << "Starting training process" << std::endl;// init, Set up the support vector machines parameterscv::Ptr<cv::ml::SVM> svm = cv::ml::SVM::create();svm->setType(cv::ml::SVM::C_SVC);svm->setC(0.1);svm->setKernel(cv::ml::SVM::LINEAR);svm->setTermCriteria(cv::TermCriteria(cv::TermCriteria::MAX_ITER, (int)1e7, 1e-6));svm->train(trainData, cv::ml::ROW_SAMPLE, labels);std::cout << "Finished training process" << std::endl;// Show the decision regionscv::Vec3b green(0, 100, 0), blue(100, 0, 0);for (int i = 0; i < I.rows; ++i) {for (int j = 0; j < I.cols; ++j) {cv::Mat sampleMat = (cv::Mat_<float>(1, 2) << i, j);float response = svm->predict(sampleMat);if (response == 1) I.at<cv::Vec3b>(j, i) = green;else if (response == 2) I.at<cv::Vec3b>(j, i) = blue;}}// Show the training dataint thick = -1;int lineType = 8;float px, py;// Class 1for (int i = 0; i < NTRAINING_SAMPLES; ++i) {px = trainData.at<float>(i, 0);py = trainData.at<float>(i, 1);circle(I, cv::Point((int)px, (int)py), 3, cv::Scalar(0, 255, 0), thick, lineType);}// Class 2for (int i = NTRAINING_SAMPLES; i <2 * NTRAINING_SAMPLES; ++i) {px = trainData.at<float>(i, 0);py = trainData.at<float>(i, 1);circle(I, cv::Point((int)px, (int)py), 3, cv::Scalar(255, 0, 0), thick, lineType);}// Show support vectorsthick = 2;lineType = 8;cv::Mat sv = svm->getUncompressedSupportVectors();for (int i = 0; i < sv.rows; ++i) {const float* v = sv.ptr<float>(i);circle(I, cv::Point((int)v[0], (int)v[1]), 6, cv::Scalar(128, 128, 128), thick, lineType);}imwrite("E:/GitCode/NN_Test/data/result_svm_non_linear.png", I);imshow("SVM for Non-Linear Training Data", I);cv::waitKey(0);return 0;
}

預(yù)測執(zhí)行結(jié)果如下：

GitHub： https://github.com/fengbingchun/NN_Test?

總結(jié)

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