需要用到两个函数:
findHomography 发现两个平面的透视变换,生成变换矩阵
perspectiveTransform 透视变换
还用到一个对象,DMatch 对象参数:
distance:每一个mathes 的距离;
trainIdx: 这个属性为我们提供了样本图像描述符列表中的描述符索引就是obj in scene图片的可以points。drawMatches()函数中的img2。
queryIdx: keypoints 是哪个的,这个属性为我们提供测试图像描述符列表中的描述符索引。就是obj 的图片的keypoints。drawMatches()函数中的img1。
imgIdx: 当样本是多张图像的话有用。
#include
#include
using namespace cv;
using namespace std;
using namespace cv::xfeatures2d;
int main()
{
Mat srcImage = imread("curry_dlt.jpg");
Mat dstImage = imread("curry1.jpg");
// surf 特征提取
int minHessian = 450;
Ptr detector = SURF::create(minHessian);
vector keypoints_src;
vector keypoints_dst;
Mat descriptor_src, descriptor_dst;
detector->detectAndCompute(srcImage, Mat(), keypoints_src, descriptor_src);
detector->detectAndCompute(dstImage, Mat(), keypoints_dst, descriptor_dst);
// matching
FlannBasedMatcher matcher;
vector matches;
matcher.match(descriptor_dst, descriptor_src, matches);
// find good matched points
double minDist = 0, maxDist = 0;
for (size_t i = 0; i < matches.size(); i++)
{
double dist = matches[i].distance;
if (dist > maxDist)
maxDist = dist;
if (dist < minDist)
minDist = dist;
}
vector goodMatches;
for (size_t i = 0; i < matches.size(); i++)
{
double dist = matches[i].distance;
if (dist < max(3 * minDist, 0.02))
{
goodMatches.push_back(matches[i]);
}
}
Mat matchesImage;
drawMatches(dstImage, keypoints_dst, srcImage, keypoints_src, goodMatches, matchesImage, Scalar::all(-1), \
Scalar::all(-1), vector(), DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS);
//imshow("matchesImage", matchesImage);
vector obj;
vector objInScene;
for (size_t t = 0; t < goodMatches.size(); t++)
{
obj.push_back(keypoints_dst[goodMatches[t].queryIdx].pt);
objInScene.push_back(keypoints_src[goodMatches[t].trainIdx].pt);
}
Mat H = findHomography(obj, objInScene, RANSAC);
vector obj_corners(4);
vector scene_corners(4);
// img1 图像的四角坐标
obj_corners[0] = Point(0, 0);
obj_corners[1] = Point(dstImage.cols, 0);
obj_corners[2] = Point(dstImage.cols, dstImage.rows);
obj_corners[3] = Point(0, dstImage.rows);
perspectiveTransform(obj_corners, scene_corners, H);
// draw line
line(matchesImage, scene_corners[0] + Point2f(dstImage.cols, 0), \
scene_corners[1] + Point2f(dstImage.cols, 0), Scalar(0, 0, 255), 2, 8, 0);
line(matchesImage, scene_corners[1] + Point2f(dstImage.cols, 0), \
scene_corners[2] + Point2f(dstImage.cols, 0), Scalar(0, 0, 255), 2, 8, 0);
line(matchesImage, scene_corners[2] + Point2f(dstImage.cols, 0), \
scene_corners[3] + Point2f(dstImage.cols, 0), Scalar(0, 0, 255), 2, 8, 0);
line(matchesImage, scene_corners[3] + Point2f(dstImage.cols, 0), \
scene_corners[0] + Point2f(dstImage.cols, 0), Scalar(0, 0, 255), 2, 8, 0);
imshow("平面对象识别", matchesImage);
waitKey(0);
return 0;
}