Digital image watermark is an invisible mark embedded in an image that can be used for copyright protection. The current paper proposes a new watermarking scheme by improving image normalization based watermarking (INW). Image normalization is based on the moments of the image, however, in general, RST attacks bring the image boundary cropping and the moments are not preserved original ones. Thereafter the normalized images of before and after are not same form. To solve the cropping problem of INW, Invariant Centroid (IC) is proposed and the only central region(R), which has less cropping possibility by RST, is used for normalization. In addition, the watermark is embedded and detected in the normalized form of the image. Experimental results demonstrated that the proposed watermarking scheme is robust to RST attacks with cropping.