Invisible Image Watermarking Using Z Transforms (IIWZT).

This paper presents an invisible image watermarking technique in frequency domain through Z transform, with a hiding capacity of 1.5 bpB (1.5 bits per byte). Z(re(i omega)) is a complex variable comes from Laplace transformation has two parameters, r denotes radius of Region of convergence and omega denotes angle respectively. In this technique (2 *2) sub matrix is taken from source image and converted into 1-diamensional (1*4) array which undergoes Z-transform with a is set of angular frequency(omega). 2 bits of secret message is embedded including the complex conjugate pair where multiple embedding is done. First co efficient is used for tuning purpose and not embedding for information. This process is repeated until exhaustion of secret image. Inverse Z transform is done at end to convert the image from frequency domain to spatial domain. Experimental result shows good PSNR and image fidelity which analytically suggest that the proposed scheme obtains better secrecy with improved fidelity.