affine transform coordinate

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Hi,

how can I transform a Coordinate (X/Y) with a 3x2 Transform Matrix?

For example, I have an image (img1) of 2048x2048 px, transform it (apply some rotation and translation) and then get img2. Now I want to know, where the pixel, which was at the point P(100/150) in img1, is in img2?

It does not have to be totally accurate, some pixels off is no problem. Is there any method to achieve this in OpenCV ?