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### Perspective Transform using Chessboard

Hey,

I need some help with this problem: I have a camera that takes a picture of something on a horizontal plane with a specific angle. That creates a perspective transform of this "something". And I would like to get this picture as if I would look down from top of it.

What I did already and one thing that I don't know how to do:

1. I placed a chessboard there.
2. I find the corners of the chessboard.
3. ???
4. cvGetPerspectiveTransform
5. cvWarpPerspective

My problem is point 3. I have to find out Source and Destination Points which depend on the corners of the chessboard and the width of the picture that was taken, because they show the transformation. Source is easy: (0,0), (Width, 0), (0,Height) and (Width,Height), because I want the whole picture to be transformed. Destination however is difficult for me. I don't know how to find those points. I want that the whole picture (Not just the part with the chessboard inside) is transformed within a single step. Like in the picture below. I would appreciate any help.

Greetings and my thanks in advance, Phanta

### Perspective Transform using Chessboard

Hey,

I need some help with this problem: I have a camera that takes a picture of something on a horizontal plane with a specific angle. That creates a perspective transform of this "something". And I would like to get this picture as if I would look down from top of it.

What I did already and one thing that I don't know how to do:

1. I placed a chessboard there.
2. I find the corners of the chessboard.
3. ???
4. cvGetPerspectiveTransform
5. cvWarpPerspective

My problem is point 3. I have to find out Source and Destination Points which depend on the corners of the chessboard and the width of the picture that was taken, because they show the transformation. Source is easy: (0,0), (Width, 0), (0,Height) and (Width,Height), because I want the whole picture to be transformed. Destination however is difficult for me. I don't know how to find those points. I want that the whole picture (Not just the part with the chessboard inside) is transformed within a single step. Like in the picture below. I would appreciate any help.

Greetings and my thanks in advance, Phanta