Abstract—This paper proposes an imperceptible watermarking scheme for digital fundus images. It is a pooled approach of two schemes proposed in [1] and [2]. Hiding a large amount of data (image, audio, text) file into color BMP images proposed in [1].It could achieve the better capacity in irreversible way which is not suitable for fundus images. The difference expanding method proposed for medical images in [2]. It suffered from imperceptibility. Hence, these two schemes were combined in the proposed scheme by addressing better capacity, imperceptibility, reversibility and robustness. The embedding process in the proposed scheme involves two steps. First step selects the pixel according to the color characteristics of the fundus images. Second step embeds the secret information into selected pixels by using the difference expanding method of the two pixels from different color planes. It is known as intra-plane difference expanding. It embeds more than one bit at each byte in one pixel of the fundus image and give us imperceptible results. This scheme is robust to statistical and visual attacks. The comparison results showed the improvement of imperceptivity to 15% in the proposed scheme with respect to the scheme proposed in [1]. It also identified that that 30000 bits is the optimum size of the watermark with good level of imperceptibility which is above 60 dB at an average.

Index Terms—Fundus image processing; image watermarking; image authentication; integer transforms.

F. S.Poonkuntran is with the Royal College of Engineering and Technology, Akkikavu, Thrissur-680604, Kerala, India. He is working as an assistant professor in the department of computer science and engineering.He is currently doing his research studies in Manonmaniam Sundaranar University, Tirunelveli-627012, Tamilnadu, India. (Corresponding Author,Phone: 91-4885-271175; mobile: 91-9894432890 fax: 04885-289043;).
S. Dr.R.S.Rajesh is with the Manonmaniam Sundaranar University, Tirunelveli-627012, Tamilnadu, India. He is working as reader in the department of computer science and engineering. (Phone: 91-462 – 2330935,Mobile: 91-94438 69904).
T. P. Eswaran is with the Manonmaniam Sundaranar University, Tirunelveli-627012, Tamilnadu, India. He is working as research scholar in the department of computer science and engineering. (Mobile:91-9865022233).

Cite: S.Poonkuntran, R.S.Rajesh and P.Eswaran, "Imperceptible Watermarking Scheme for Fundus Images Using Intra-Plane Difference Expanding," International Journal of Computer and Electrical Engineering vol. 1, no. 4, pp. 426-430, 2009.