Embedding Binary Watermarks in Dual-Tree Complex Wavelets Domain for Access Control of Digital Images

This paper investigates embedding binary watermarks in digital images in dual-tree complex wavelet transform domain due to its rich direction selection, shift invariance and higher robustness. However, embedding binary watermarks directly into the wavelet coefficients does not work well. Two watermarking schemes are proposed, coefficients swapping is to embed the watermark in the low-frequency coefficients by selecting those 2×2 blocks with high-energy and swapping the two coefficients in the median range. Whereas a group of high-pass complex frequency coefficients are quantized so that the quantized coefficients lie in the middle of the quantization range and the changes are distributed among the coefficients. Experimental results conducted on 100 images achieve about 96% and 92% detection rate for the low-pass and high-pass frequency coefficients-based schemes. Robustness tests against several common signal processing attacks such as additive noise, median filtering and lossy JPEG compression confirm the superior performance of the proposed schemes.