Specifications

Geometric Transforms
11-11
11
GetRotateShift
Computes shifts for iplRotate, given
the rotation center and angle.
void iplGetRotateShift(double xCenter , double yCenter ,
double
angle , double* xShift , double* yShift );
xCenter , yCenter Coordinates of the rotation center for which you
wish to compute the shifts.
angle The angle (in degrees) to rotate the image around
the point with coordinates (
xCenter , yCenter ).
xShift , yShift Output parameters: the shifts along the x-andy-
axes to be passed to
iplRotate() in order to
achieve rotation around the specified center
(
xCenter , yCenter ) by the specified angle .
Discussion
Use the function iplGetRotateShift() if you wish to rotate an image
around an arbitrary center (
xCenter , yCenter ) rather than the origin (0,0).
Just pass the rotation center (
xCenter , yCenter ) and the angle of rotation
to
iplGetRotateShift(), and the function will recompute the shifts
xShift , yShift .
Calling
iplRotate() with these xShift and yShift is equivalent to
rotating the image around the center ( xCenter , yCenter ).
Example 11-2 Rotating an Image
int example111( void ) {
IplImage *imga, *imgb;
const int width = 5, height = 5;
__try {
int i;
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