In this paper, a robust and high capacity digital image watermarking scheme using discrete cosine transform is proposed. The original image is first segmented into mxn image blocks and each image block is decomposed by discrete cosine transform. Then, the twelve representative DCT coefficients are selected for watermark embedding by adaptive quantization of the selected coefficients. Experimental results show the proposed method is capable of embedding 4096 bits of information in images with dimensions 512 x 512 pixels and is robust to various attacks such as JPEG compression, Gaussian lowpass filter, which outperforms the existing watermarking algorithm. © 2009 IEEE.