Image watermarking using wavelets

This paper proposes a novel image watermarking scheme. This technique uses a 2-D discrete wavelet transform to decompose an image into various frequency channels. A scaled image is used as the watermark and inserted into a mid-frequency wavelet channel. The watermark embedded image is produced by taking the inverse 2-D discrete wavelet transform of the altered wavelet decomposition. The image size, the non-zero scaling factor, the channel in which the watermark is inserted, and the wavelet transform filters can be used as security keys for the extraction of the inserted watermark. The propose watermark extraction technique is independent of the original image. A compromise between visually perceptible artifacts and resiliency in preserving the watermark from attacks by JPEG compression, median filtering, and image cropping can be achieved by adjusting the scaling factor.