OpenCV C++ to C conversion -

if in opencv c++ api while creating rotation matrix if write

       mat rot_matrix = getrotationmatrix2d(src_center, angle, 1.0); 

then how should write in opencv c? should write instead of mat? this:-

         cvmat* rot_mat =cv2drotationmatrix( center, angle, scale, rot ); 

is above declaration correct? if yes, how can represent in wrap affine function? this:-

         cvwarpaffine( src, dst, rot_mat); 

i think bit confused according our little chat @ comments sector, decided write answer try make bit clearer.

first original question wrote mat indeed c++ form.

in c use cvmat function cv2drotationmatrix() takes cvmat * part of parameters therefore can used that:

 cv2drotationmatrix(center,angle,scale,rot_mat); 

where:

• center cvpoint2d32f, center of rotation in source image (width/2,height/2).
• angle – desired rotation angle(in degrees).
• scale – isotropic scale factor (1 means picture kept @ same size)
• mapmatrix – pointer destination matrix (your 2x3 matrix used rotation matrix)

now rot_mat hold rotation matrix:

where:

now calculate position of each pixel after rotating whole picture in x degrees (an affine transformation on pixels/pciture/image).

at stage have rotation matrix being used in affine transformation , want affine transformation (rotating image) can use function cvwarpaffine()

in our case:

cvwarpaffine( src, dst, rot_mat ); 

where:

• src – source image
• dst – destination image
• rot_mat our mapmatrix(transformation matrix)

*there fourth parameter flag default o.k our case.

what does?

transforms source image using specified matrix:

*or in simpler words described before "just" calculates new position each pixel after rotation (using rotation matrix - input affine function).

rot_mat should 2x3 mat - can create calling cvcreatemat().

src,dst iplimage * (because said it's c code).

*the technical aspect of function from: http://opencv.willowgarage.com/documentation/geometric_image_transformations.html