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Watermark robustness against both geometric and signal processing attacks is still challenging in the watermarking community. In this work, we propose an approach to increase the watermark detection rate. The novel feature of the method resides in pre-processing the image before the embedding process, and involves no interaction with other improvements. It is based on the following idea: given the same watermarking scheme, some images are naturally more appropriate for the embedding process as they obtain better detection rates than others. In the Fourier scheme for example, it was observed that lower amplitude variations at Fourier coefficients correspond to a better detection rate. We theoretically justify these findings and demonstrate that by applying a dedicated low-pass filtering on the magnitude of the frequency bands the watermark detection rate is significantly improved.

Digital image watermarking is an active research field since it provides protection, security, and authenticity of data. This paper presents development and implementation of a blind and robust watermarking application for ID images under a print-cam system. In the present case, the images are watermarked and printed on ID cards and then detected freehandedly with a smartphone camera. In order to design an efficient and robust image watermarking application, the attacks produced in print-cam processes, such as geometric distortions, must be resolved. Accordingly, the proposed watermarking approach is applied in the Fourier domain. Then, a frame-based projective rectification is integrated to deal with geometric distortions by using detection of Hough lines. Moreover, better robustness against print-cam watermarking attacks was achieved compared with the existing methods, and an Android application was designed and implemented based on the proposed scheme.