This work presents a method with a low computational complexity to embed a multi-tone watermark. A halftone image is obtained using regular error diffusion, while the other image is obtained using the proposed Generalized Noise-Balanced Error Diffusion (GNBEDF) when, simultaneously, considering the properties of the watermark and the first halftone image. The proposed method makes the bi-level watermarking becomes a special case to multi-tone watermarking. The bi-level watermark decoding can be achieved via printing the two halftone images onto two transparencies, then superimposing them together to reveal the watermark pattern. However, given that the multi-tone watermark is involved, the proposed Gaussian Difference (GD) approach is required to perform the decoding to produce a decoded multi-tone watermark. Moreover, the Single Image Decodable GNBEDF (SID-GNBEDF) is also proposed for the case where only one embedded image is available in the decoder. A lowpass filter obtained by Least-Mean-Square is employed throughout this study to assess the image quality. As demonstrated in experimental results, the proposed approach can guard again reasonable attacks (cropping and print-and-scan).