Salt-and-pepper image watermarking system for IHC evaluation criteria

This paper presents an image watermarking system for the IHC evaluation criteria (ver.3) which require tolerance against both compression and cropping. To meet the requirement, our system repeatedly embeds watermark information into the DCT domain with significantly high watermark strength. On the other hand, to keep high image quality, only one DCT coefficient is used for each watermark bit. Thus, the system adds spike noise (or salt-and-pepper noise) to the DCT domain at embedding. The experimental results show that the watermarking system satisfies the IHC criteria ver.3 and achieves high performance in the contest categories called highest tolerance and highest image quality. Specifically, in the highest tolerance category, the embedded watermark information is detected without error even against compression reducing the file size by 0.5 of its original size. On the other hand, in the highest image quality, PSNR is not lower than 41 dB without error against the specified compression ratio, namely, 4%.