ORB is very fast, but it always too few points,which make me awkward. So I have made a such mask
I want to find 10 keypoints in every white rectangle by ORB. But as the documentation here. The first argument just mean:
The maximum number of features to retain.
This is my current method
//OpenCV 3.3.1 project
#include<opencv.hpp>
using namespace std;
using namespace cv;
Mat highlight(Mat, Mat);
int main() {
Mat emptyImg = imread("test.jpg", 0);
Mat test = emptyImg.clone();
Mat mask(5, 5, CV_8UC1, Scalar(0));
for (int i = 0; i < mask.rows; i++) {
uchar* data = mask.ptr<uchar>(i);
for (int j = 0; j < mask.cols; j++)
if ((i + j) % 2 == 0)
data[j] = 255;
}
resize(mask, mask, emptyImg.size(), 0, 0, INTER_NEAREST);
Mat labels, stats, centroids;
int nmask = connectedComponentsWithStats(mask, labels, stats, centroids, 4, CV_16U);
stats.convertTo(stats, CV_8U);
vector<Mat> rects;
for (int i = 1; i < nmask; i++) {
uchar* data = stats.ptr<uchar>(i);
Mat temImg = Mat(mask.size(), CV_8UC1, Scalar(0));
rectangle(temImg, Rect(data[0], data[1], data[2], data[3]), Scalar(255), FILLED);
rects.push_back(temImg);
}
Ptr<ORB> detector = ORB::create(10);
vector<KeyPoint> keypoints_empty;
for (int i = 0; i < nmask - 1; i++) {
vector<KeyPoint> tem_keypoints_empty;
detector->detect(emptyImg, tem_keypoints_empty,rects[i]);
//string name="rects";
//imshow((name + to_string(i)).c_str(), rects[i]);
//waitKey(1);
keypoints_empty.insert(keypoints_empty.end(), tem_keypoints_empty.begin(), tem_keypoints_empty.end());
}
Mat showImg=highlight(emptyImg,mask),resultImg;
drawKeypoints(showImg, keypoints_empty, resultImg,Scalar(0,255,255));
imshow("keyImg", resultImg);
waitKey();
return 0;
}
Mat highlight(Mat srcImg, Mat mask) {
if (srcImg.size != mask.size) {
cout << "Your two images tried to highlight have different SIZE.\n";
exit(1);
}
if (mask.channels() != 1)
cvtColor(mask, mask, COLOR_BGR2GRAY);
if (mask.type() != CV_8UC1)
mask.convertTo(mask, CV_8UC1);
threshold(mask, mask, 0, 255, THRESH_BINARY_INV + THRESH_OTSU);
cvtColor(mask, mask, COLOR_GRAY2BGR);
if (srcImg.channels() != 3)
cvtColor(srcImg, srcImg, COLOR_GRAY2BGR);
if (srcImg.type() != CV_8UC3)
srcImg.convertTo(srcImg, CV_8UC3);
dilate(mask - Scalar(0, 0, 255), mask, Mat(), Point(-1, -1), 2);
return srcImg - mask;
}
I don't think any problem in my code, but the resultImg make me confused very much..
As we see, there are two problem in my method.
- There are some keypoints out of the white rectange
- Some rectangle have a few keypoints even have none
Can anybody can help me out?
