asked 2012-08-28 10:04:42 -0500
This post is a wiki. Anyone with karma >50 is welcome to improve it.
sorry probably it's a stupid question :) it's possible to apply a homography to the coordinates of a point?
for example in his code:
double X;
double Y;
std::vector<KeyPoint> key_filtered;
for( int i=0; i<(int)keypoints.size(); i++)
{
double x = keypoints[i].pt.x, y = keypoints[i].pt.y;
if((X >= corner[0].x && X <= corner[1].x) && (Y >= corner[0].y && Y <= corner[2].y)){
key_filtered[j]=keypoints[i];
j++;
}
}
i want apply the homography "inv" to "x" and "y"....
answered 2012-08-28 10:38:12 -0500
This post is a wiki. Anyone with karma >50 is welcome to improve it.
I guess you're looking for
void perspectiveTransform(vector<Point> origPoints, vector<Point> transformedPoints, Mat h)
where h is your (inverted) homography matrix.
Here's a little code example on how to use it:
void perspectiveTransformTest()
{
// source quadrangle
vector<Point2f> src;
src.push_back(Point(0,0));
src.push_back(Point(2,0));
src.push_back(Point(2,2));
src.push_back(Point(0,2));
// transformed quadrangle
vector<Point2f> dst;
dst.push_back(Point(1,0));
dst.push_back(Point(2,1));
dst.push_back(Point(1,2));
dst.push_back(Point(0,1));
// compute transformation matrix
Mat H = getPerspectiveTransform(src, dst);
// apply transformation matrix to source quadrangle
vector<Point2f> dst2;
perspectiveTransform(src, dst2, H);
// display results
for (int i=0; i<4; ++i)
{
cout << "dst: p" << i << "(" << dst[i].x << "," << dst[i].y << ")\t dst2: p" << i << "(" << dst2[i].x << "," << dst2[i].y << ")" << endl;
}
}
and that's the output:
dst: p0(1,0) dst2: p0(1,3.33067e-016)
dst: p1(2,1) dst2: p1(2,1)
dst: p2(1,2) dst2: p2(1,2)
dst: p3(0,1) dst2: p3(1.11022e-016,1)
Note: perspectiveTransform() doesn't accept KeyPoints. Use The Points stored in KeyPoint instead:
vector<KeyPoint> keypoints;
// ....
vector<Point2f> points;
for(vector<KeyPoint>::iterator it=keypoints.begin(); it!=keypoints.end(); ++it)
{
points.push_back(it->pt);
}
answered 2012-08-30 03:48:19 -0500
This post is a wiki. Anyone with karma >50 is welcome to improve it.
i already try
i write: perspectiveTransform(keypoints[i],temp,inv)
but he give me an error : invalid initialization of reference of type 'const cv::_InputArray&' from expression of type 'cv::KeyPoint'
Asked: 2012-08-28 10:04:42 -0500
Seen: 439 times
Last updated: Aug 30 '12