Blind and invisible watermarking techniquies for color images 227 Blind and invisible watermarking techniquies for color images Soni Atmik M. 1 . Metkar Shilpa P. 1 . Lande Pankaj U. 2 1 College of Engineering, Pune, India 2 University of Pune, Pune, India 1. Introduction With the recent proliferation and success of the internet, to- gether with the availability of relatively inexpensive digital recording and storage devices has created an environment in which it becomes very easy to obtain, replicate and dis- tribute digital content without any loss in quality. This has become a great concern to the multimedia content (music, video and image) publishing industries, because technolo- gies or techniques to protect intellectual property rights for digital media and to prevent unauthorized copying did not exist. Exactly identical copies of digital information, be it images, text or audio, can be produced and distributed easily. In such a scenario, who is the artist and who the plagiarist? It’s impossible to tell or was, until now. Encryption technologies can be used to prevent unauthor- ized access to digital content. However, encryption has its limitations in protecting intellectual property rights because once digital content gets decrypted; there is nothing to prevent an authorized user from illegally replicating it. Another technology is obviously needed to help establish and prove ownership rights, then track content usage, ensure authorized access, facilitate content authentication and prevent illegal replication. This need attracted attention from the research community and industry leading to creation of new information hiding form, called Digital Watermarking. The basic idea of digital watermarking is to create a metadata containing informa- tion about the digital content to be protected, and then hide the metadata within that content. The information stored as metadata can have different formats, such as character string or binary image pattern. The watermarking technique is one of the solutions to different issues of copyright protection, image authenti- cation, proof of ownership, etc. This technique embeds information so that it is not easily perceptible, that is, the viewer cannot see any information embedded in the con- tents. There are still several important issues existing in the watermarking system. • First, the embedded watermark should not degrade the quality of the image and should be perceptually invisible to maintain its protective secrecy. • Second, the watermark must be robust enough to resist common image processing attacks and not be easily removable, only the owner of the image is able to extract the watermark. • Third, the blind Watermarking technique is necessary since sometimes it is not easy to obtain the original image or original watermark during Extraction, furthermore, a lot of space is needed for storing the original image and original watermark. Watermarking techniques are mainly classified into 1) spa- tial domain [1] watermarking techniques, where watermark is embedded directly by changing pixels value, and 2) frequency domain [2] the pixel values are transformed into another domain by applying appropriate transform. N. Nikolaidis and I. Pitas give an overview of Digital Image Watermarking [1]. They described the watermarking schemes and data hiding techniques for copyright protection of still images. They also described some recent research results on that field and a number of distinct application areas, each with different requirements and limitation. The Spread -spectrum communication is robust against many types of interference and jamming [3]. Cox et al. [4] pro- posed a watermarking method to embed a watermark by the spread-spectrum technique. The watermark is inserted in the perceptually significant portion of an image where in a predetermined range of low frequency components exclude the dc component. The watermark is spread over many frequency coefficients, so that the number of coefficients which are modified is very small and difficult to detect. Podilchuk and Zeng [5] improved Cox’s method and added the model of the just noticeable difference (JND) to select the maximum length and maximum power water- mark sequence. Their method can be used for both the DCT and the discrete wavelet transform (DWT) domains [5]. In [6], the watermark was embedded by quantizing the S.J. Pise (ed.), ThinkQuest 2010, DOI 10.1007/978-81-8489-989-4_42, © Springer India Pvt. Ltd. 2011