A Self-Adaptive Spatial-Frequency Domain Conjoint Watermarking Algorithm for Binary Images

The problem of watermarking for binary images in the framework of wavelet transform is addressed. At first, wavelet transform is implemented to the original binary image, and then those areas that have more rich veins were selected to be inserted watermark by analyzing the wavelet coefficients. The selection of the areas and the locations to insert watermark is controlled by a secret key. Watermark is inserted by changing pixel intensities in spatial domain and the length of watermark is adaptive to the veins richness of images. The proposed algorithm is simple and feasible. And simulations show that it is invisible and robust. It is an effective watermarking algorithm for binary images.