object detection: get Border of rotating Objects

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Hello, I'm searchig for a tool which helps me indemnify objects (cars motorhomes etc).
We have thousend of pictures of cars and motorhomes, all centered in the pictures, all above the same background (white walls), each object rotates in fixed steps per picture. I have to erase the background on every picture to transparency.
Do You think OpenCv can help me - I think Cascade Classifier or Shape Contexts are not the correct way.
Thank You for Your Advice.