Toward Achieving a Trade-Off for SVD-Based Image Watermarking Using Mojette Transform

Imperceptibility and robustness are a part of trade-off components in image watermarking schemes and become one of the most studied in this field. Increasing imperceptibility usually will reduce the robustness, conversely, increasing the robustness may reduce the imperceptibility. This study is intended to overcome this challenge by proposing an image watermarking scheme using the Mojette transform to increase both imperceptibility and robustness. This transform is derived from the Radon transform which has some advantages in geometrical representations that have benefits for imperceptibility and robustness analyses. For evaluation purposes, the performance of the Mojette transform is evaluated on an image watermarking scheme in the singular value decomposition as this domain is stable in response to various image processing operations and also has a simple computation. The use of the Mojette transform in the proposed method involves both main image watermarking processes, which are watermark embedding and extraction. Towards achieving the trade-off of the watermarking requirement, the embedding watermark is designed at the maximum capacity. This means that the watermark is designed at the same size as the host image although it is embedded in various levels of scale factor. The watermarked image is then evaluated in the imperceptibility aspect, and the extracted watermark is evaluated in the robustness aspect after some attacks are applied to the watermarked images. Experimental results on some test images show that embedding the watermark at the maximum size using the proposed method kept producing a good perceptible watermarked image without reducing imperceptibility and robustness. For example, the imperceptibility of the watermarked image at 1% of the embedded scale factor could produce the visual quality at 45.2373 dB and the watermark could be extracted well although some attacks have occurred on the watermarked image. Almost all of the extracted watermarks after being distorted by nosing, filtering, compression, rotation, cropping, and flipping attacks have normalized correlation coefficients above 95%. Although the payload capacity of the watermark still needs further analysis, however, this study shows that the Mojette transform can contribute toward achieving the trade-off in the image watermarking requirements.