You specify some movement in the x-direction, from 640.5 to 639.5. But most of the movement in that direction comes from the expansion in the y-direction.
Perhaps you don't understand perspective distortions. Imagine this wasn't an invented image, but a photo of a fence, with vertical posts and horizontal bars. But the camera is at an angle so the horizontal bars converge towards the right. A perspective correction would have the same effect as straightening the camera angle, making the sensor parallel to the fence. This will make the bars horizontal, but will also move the vertical posts. This is because the posts on the right side were more distant from the camera so were closer together in the photo, and straightening the photo will move those posts apart.
Perhaps you don't understand perspective distortions. Imagine this wasn't an invented image, but a photo of a fence, with vertical posts and horizontal bars. But the camera is at an angle so the horizontal bars converge towards the right. A perspective correction would have the same effect as straightening the camera angle, making the sensor parallel to the fence. This will make the bars horizontal, but will also move the vertical posts. This is because the posts on the right side were more distant from the camera so were closer together in the photo, and straightening the photo will move those posts apart.
Statistics: Posted by snibgo — 2019-12-10T10:08:30-07:00