For copyright protection, the robustness of a watermarking scheme against various attacks is an essential requirement. Many proposed robust watermarking schemes may achieve good robustness but at the expense of sacrificing the good quality of the watermarked image. This work, therefore, proposes a transparent robust watermarking scheme, which embeds the watermark (or the secret information) adaptively in the discrete cosine transform (DCT) domain. The proposed scheme is blind as the original image is not needed, and only an image-dependent dual key containing the watermark locations and the scaling factors is required for watermark extraction. This content adaptive replacement embedding technique can guarantee preservation of good visual quality of a watermarked image. The watermarking scheme is shown to be highly robust for a wide range of attacks, including JPEG compression, quantization, additive noise, rotation, cropping, scaling, and filtering. Compared with other existing DCT-domain watermarking methods, the proposed watermarking method can achieve higher robustness performance, while retaining better quality of the watermarked image.