用VLFeat库进行SIFT特征提取（C++ 实现）

说明：

具体改动：用Mat类型替代原始代码中的IPlImage

#include <iostream>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <stdio.h>//标准输入输出头文件，编写C语言中，常用到printf()和scanf()函数.
#include <string.h>//是C版本的头文件，包含比如strcpy、strcat之类的字符串处理函数。

#define TRUE 1//define 用于简单的字符替换

extern "C"{
#include <vl/generic.h>
#include <vl/sift.h>
}

using namespace cv;
using namespace std;

int main(int argc, char* argv[])
{

cout << "SIFT特征提取演示程序" << endl;
VL_PRINT("Hello world!\n");

Mat img_1 = imread("1.jpg", 0);
int noctaves = 4, nlevels = 2, o_min = 0;

// noctaves=(int)(log(min)/log(2));
//在sift.h头文件中有 typedef float vl_sift_pix 声明

vl_sift_pix *ImageData = new vl_sift_pix[img_1.cols*img_1.rows];
for (int i = 0; i < img_1.rows; i++)
{
uchar *Pixel = img_1.ptr<uchar>(i);
for (int j = 0; j < img_1.cols; j++)
{
ImageData[i*img_1.cols + j] = Pixel[j];
}
}
// 定义VlSiftFilt结构体指针
VlSiftFilt *SiftFilt = NULL;
// 创建一个新的sift滤波器
SiftFilt = vl_sift_new(img_1.cols, img_1.rows, noctaves, nlevels, o_min);

int KeyPoint = 0;
int idx = 0;
if (vl_sift_process_first_octave(SiftFilt, ImageData) != VL_ERR_EOF)
{
while (TRUE)
{
//计算每组中的关键点
vl_sift_detect(SiftFilt);
//遍历并绘制每个点
KeyPoint += SiftFilt->nkeys;//检测到的关键点的数目
cout << "关键点数目：" << endl << KeyPoint << endl;
VlSiftKeypoint *pKeyPoint = SiftFilt->keys;//检测到的关键点
for (int i = 0; i<SiftFilt->nkeys; i++)
{
VlSiftKeypoint TemptKeyPoint = *pKeyPoint;
pKeyPoint++;
circle(img_1, cvPoint(TemptKeyPoint.x, TemptKeyPoint.y), TemptKeyPoint.sigma / 2, CV_RGB(255, 0, 0));

idx++;
//计算并遍历每个点的方向
double angles[4];
int angleCount = vl_sift_calc_keypoint_orientations(SiftFilt, angles, &TemptKeyPoint);//计算关键点的方向
for (int j = 0; j<angleCount; j++)
{
double TemptAngle = angles[j];
printf("%d: %f\n", j, TemptAngle);
//计算每个方向的描述
float *Descriptors = new float[128];
vl_sift_calc_keypoint_descriptor(SiftFilt, Descriptors, &TemptKeyPoint, TemptAngle);
int k = 0;
while (k<128)
{
printf("%d: %f", k, Descriptors[k]);
printf("; ");
k++;
}

printf("\n");
delete[]Descriptors;
Descriptors = NULL;
}
}
//下一阶
if (vl_sift_process_next_octave(SiftFilt) == VL_ERR_EOF)
{
break;
}
//free(pKeyPoint);
KeyPoint = NULL;
}
}
vl_sift_delete(SiftFilt);
delete[]ImageData;
ImageData = NULL;
namedWindow("Source Image", 1);
imshow("Source Image", img_1);

waitKey(0);

return 0;
}

运行效果：

运行报错：提示缺少vl.dll[b]？

将安装vlfeat\bin\win32路径下的vl.dll拷贝到项目生成的debug文件夹再编译就OK了.