warpPerspective 和perspectiveTransform 有什么区别？

Question

I have used four sets of points to get a perspective transform matrix. Then using warpPerspective to transform the matrix A to matrix B . Point a from Mat A. I want to get the new point a position in mat B. But warpPerspective cannot do that, while perspectiveTransform can.

Here I want to know if the position that perspectiveTransform gets is the same as the position in matrix B by using warpPerspective .

So, what is the difference between warpPerspective and perspectiveTransform ?

Mat trans = getPerspectiveTransform(dst, gpsPoints);
warpPerspective(A, B, trans, image.size());
Point2f a = Point2f(..., ...);         //were known
vector<Point2f> obj(1);
obj[0] = a;
vector<Point2f> b; 
perspectiveTransform(obj, b, trans);//if the new point in B is c, is c equals to b?

Answer 1

warpPerspective works for images. In other words, warpPerspective can warp image A and put the result in B using the H (Homography or warpMatrix) so it has the following struct:

void warpPerspective(InputArray src, OutputArray dst, InputArray M, Size dsize, int flags=INTER_LINEAR, int borderMode=BORDER_CONSTANT, const Scalar& borderValue=Scalar())

src is the Mat you want to warp, dst where the result will be stored.

perspectiveTransform works for set of points. It applies the H (Homography or warpMatrix) on set of points (which are in vector for example) and put the results in another vector . The results are the points in the first vector after applying the warping. it has the following struct:

void perspectiveTransform(InputArray src, OutputArray dst, InputArray m)

where src is the input points, dst is the results of warping the input points.

Conclusion :

Mathematically , they both do the same thing which is warping a set of point using H.

Technically , warpPerspective do this on the coordinates of the Mat and move the pixel value(color) to a new pixel. perspectiveTransform , it just compute the new coordinate of the point and store it in the new vector .