A Fragile Watermarking Based on Legendre Transform for Color Images (Fwltci)
Ghosal S.K, Mandal J.K · Signal & Image Processing An International Journal · 2013
In this paper, a Legendre transformation (LT) based fragile watermarking technique has been proposed for color image authentication.The authentication is done by inserting the watermark into the carrier images in transform domain.An initial pixel adjustment has been applied on each pixel component to keep the pixel value positive and less than or equal to the maximum.The Legendre transformation (LT) is applied on each pair of pixel components of the carrier image in row major order.The first transformed component can fabricate two bits whereas the second component fabricates three bits of authenticating watermark starting from the least significant bit position (LSB-0).A post adjustment is also applied to keep the embedded components closer to the original without affecting the least three significant bits.The inverse Legendre transform (ILT) is applied on each adjusted pair to re-generate the watermarked image.During inverse transform, at if the second pixel component of the adjusted pair become fractional, then the LSB-2 of the first component is set to one; otherwise is set to zero.The reverse procedure is applied at the destination to retrieve back the watermark which in turn is verified for authentication through a message digest.Experimental results conform that the proposed algorithm has improvised the payload and PSNR over Varsaki et.al's Method [6] and LTCIA technique [7].