Learning OpenCV, 2nd Edition

transform the individual pixels, but rather to move them from one place in the image to

another. This is the job of cv::warpPerspective().

If you want to solve the inverse problem to find the most probable perspective

transformation given many pairs of corresponding points, use

cv::getPerspectiveTransform() or cv::findHomography().

cv::phase()

void cv::phase(

cv::InputArray x, // Input array of x-components

cv::InputArray y, // Input array of y-components

cv::OutputArray dst, // Output array of angles (radians)

);

dst

i

= atan2 y

i

,†x

i

( )

†

cv::phase() computes the azimuthal (angle) part of a Cartesian-to-polar conversion on a two-

dimensional vector field. This vector field is expected to be in the form of two separate single--channel

arrays. These two input arrays should, of course, be of the same size. (If you happen to have a single two--

channel array, a quick call to cv::split() will do just what you need.) Each element in dst is then

computed from the corresponding elements of x and y as the arctangent of the ratio of the two.

cv::polarToCart()

void cv::polarToCart(

cv::InputArray magnitude, // Input array of magnitudes

cv::InputArray angle, // Input array of angles

cv::OutputArray x, // Output array of x-components

cv::OutputArray y, // Output array of y-components

bool angleInDegrees = false // degrees (if true) ...