Watermarking of images

摘要

A bit stream is decoded to generate first quantized DCT-coefficients. The first quantized DCT-coefficients are inversely quantized using a first quantization table (106), thereby generating DCT-coefficients. The resulting DCT-coefficients are quantized using a second quantization table (107), thereby generating second quantized DCT-coefficients. Elements in the second quantization table (107) are smaller in value than those in the first quantization table (106). Predetermined additional information is embedded into the second quantized DCT-coefficients. The second quantized DCT-coefficients having the additional information embedded therein are encoded to produce a bit stream having the additional information embedded therein. The second quantization table (107) is set to be smaller in value than the first quantization table (106).