A copyright protection scheme based on chaos and secret sharing techniques is proposed. Instead of modifying the original image to embed a watermark in it, the proposed scheme extracts a feature from the image first. Then, the extracted feature and the watermark are scrambled by a chaos technique. Finally, the secret sharing technique is used to construct a shadow image. The watermark can be retrieved by performing an XOR operation between the shadow images. The proposed scheme has the following advantages. Firstly, the watermark retrieval does not need the original image. Secondly, the scheme does not need to modify the original image for embedding the watermark. Thirdly, compared with several schemes, the scheme is secure and robust in resisting various attacks.