30-07-2012, 02:51 PM
Implementation of a Visible Watermarking in a Secure Still Digital Camera Using VLSI Design
Implementation of a Visible Watermarking.pdf (Size: 355.16 KB / Downloads: 50)
Abstract.
Watermarking is the process that embeds data called a watermark, a tag, or a label into a
multimedia object, such as images, video, or text, for their copyright protection. According to human
perception, the digital watermarks can either be visible or invisible. A visible watermark is a secondary
translucent image overlaid into the primary image and appears visible to a viewer on a careful inspection.
The invisible watermark is embedded in such a way that the modifications made to the pixel value are
perceptually not noticed, and it can be recovered only with an appropriate decoding mechanism. This paper
presents new very large scale integration (VLSI) architecture for implementing two visible digital imagewatermarking
schemes. The proposed architecture is designed to aim at easy integration into any existing
digital camera framework.
Keywords: Digital watermarking, JPEG encoder, MATLAB, spatial domain watermarking, still digital
camera, visible and invisible watermarking
Introduction
Watermarking is the process that embeds data called a watermark, a tag, or label into a multimedia object
such that the watermark can be detected or extracted later to make an assertion about the object. The object
may be an image, audio, video, or text. Whether the host data is in spatial domain, discrete cosinetransformed,
or wavelet-transformed, watermarks of varying degree of visibility are added to present media
as a guarantee of authenticity, ownership, source, and copyright protection. In general, any watermarking
scheme (algorithm) consists of three parts, such as Watermark, Encoder and Decoder and Comparator.
Watermarks and watermarking techniques can be divided into various categories. The watermarks can be
applied either in spatial domain or in frequency domain. It has been pointed out that the frequency-domain
methods are more robust than the spatial-domain techniques. On the other hand, the spatial domain
watermarking schemes have less computational overhead compared with frequency-domain schemes.
According to human perception, the digital watermarks can be divided into four categories: (1) Visible, (2)
Invisible-robust, (3) Invisible-fragile, (4) Dual
Vlsi Architecture and Implementation of the Chip
In this section, we discuss the VLSI architectures for the watermarking algorithm. We assume that both
the original image and the watermark image are stored in the memory within the digital camera framework
and are available for processing. The images may be in either a compressed format or as raw ASCII data. We
need to have a corresponding decoder to decode the image and get the uncompressed data in case it is in
compressed format.
The insertion operation for the watermarking algorithm is described in [1]. This insertion function is
simplified to using a piecewise linear model such that we have a compact and efficient hardware design. Fig.
4 shows the architecture proposed for the algorithm. The watermarking in this scheme is performed pixel by
pixel as evident from the insertion function. A register file is used to store the constants needed to scale the
image–watermark product and we store the constants.
Conclusion
In this paper, we presented a watermarking chip that can be integrated within a digital camera framework
for watermarking images. The watermarking chip can also be integrated in any existing JPEG encoder. The
chip has two different types of watermarking capabilities, in spatial domain. This algorithm does pixel-bypixel
processing, and comparable in terms of signal-to-noise ratio (SNR) values. The design can be improved
by a data path organization in which the blocks can be pipelined to obtain better throughput.