A new approach to invisible water marking of color images using alpha blending

Development of computer networking generates many benefits in cyber world. Due to this great advancement, nowadays networking facilities are available at very low cost. But unfortunately this easy access becomes a threat to information security. Watermarking is a technique that is very often used in image processing to trace copyrighted products. It can also be used to trace products which are illegally distributed without permission. In our research work, a new technique for invisible watermarking of images using alpha blending has been proposed. Alpha blending is used to display an alpha bitmap and an alpha bitmap is that one which has transparent and semi-transparent pixels. We have worked on color image and gray scale image. Gray scale image is used as watermark image which is kept hidden in the main scale image by different values of alpha in alpha blending method. This technique is actually done on each plane of the color image. The resulting image contains the information of color image and gray scale images but the main image is unseen to others. PSNR values are also calculated to check the robustness of the reconstructed image. Applying some post-processing work, this can be used in image steganography also.