import org.opencv.core.Core;

import org.opencv.core.Mat;

import org.opencv.core.MatOfKeyPoint;

import org.opencv.highgui.Highgui;

import org.opencv.features2d.*;

public class ExtractSIFT{

　　public static void main( String[] args ){

       System.loadLibrary( Core.NATIVE_LIBRARY_NAME );

    　　Mat test_mat = Highgui.imread("/home/Tian/software/meng.jpg");

    　　Mat desc = new Mat();

       FeatureDetector fd = FeatureDetector.create(FeatureDetector.SIFT);

       MatOfKeyPoint mkp =new MatOfKeyPoint();

       fd.detect(test_mat, mkp);

       DescriptorExtractor de = DescriptorExtractor.create(DescriptorExtractor.SIFT);

       de.compute(test_mat,mkp,desc );//提取sift特征

       System.out.println(desc.cols());

       System.out.println(desc.rows());

   }

   //以下代码实现了对主函数中代码的封装

    /**

     * 传入一张图片得到sift特征点

     * @param mat

     * @return

     */

    public MatOfKeyPoint getFeaturePoints(Mat mat){

        FeatureDetector fd = FeatureDetector.create(FeatureDetector.SIFT);

        MatOfKeyPoint mkp =new MatOfKeyPoint();

        fd.detect(mat, mkp);

        return mkp;

    }  

    /**

     * 获取sift特征

     * @param mat

     * @return

     */

    public Mat getFeature(Mat mat){

        Mat desc = new Mat();

        MatOfKeyPoint mkp = getFeaturePoints(mat);

        DescriptorExtractor de = DescriptorExtractor.create(DescriptorExtractor.SIFT);

        de.compute(mat,mkp,desc );//提取sift特征

        return desc;

    }

}