Calculate contour area of the object on image plane when the tilt angle of a camera have changed

[necator]

The camera is always oriented in a way that lower border of HFOV (horizontal field of view) is aligned with bottom side of the object.
Dimension of the object for reference camera tilt angle are given as well as contour area of this object on image plane. Parameters of camera (fields of view, focal length) are also known.

Is it possible to calculate new changed contour area on image plane when camera tilt angle is changed (due to changing object distance or/and camera height)?

I would be grateful if someone could point me to methods of calculations applicable here.

I have found such method as camera transform using pinhole camera model to represent object in 3d space on 2d plane, but seems that it is not what I am looking for.