Modulo arithmetic-based image watermarking and its theoretical analysis of image-quality

This paper proposes a watermarking method that hides an integer in an image by modifying the sum of the quantized discrete cosine transformed coefficients. Because modulo arithmetic-based modulation is applied to an integer to be embedded, less image distortion is achieved. Moreover, coefficients not being chosen to embed an integer are restored to their pre-quantized form, even though they are once quantized. The image-quality of a watermarked image is theoretically analyzed and is found to be superior to those of image-quality guaranteed watermarking methods.