ELECTRONIC WATERMARKING METHOD, ELECTRONIC WATERMARK DETECTING METHOD, APPARATUS AND PROGRAM

摘要

An electronic image to be electronic watermarked is spatially divided into a plurality of image areas. Pixels having such characteristics that pixel value changes are hard to visually recognize are extracted, as adaptive pixels, from each of the image areas. The pixel values of the adaptive pixels are changed between the image areas and in the time direction in accordance with the electronic watermarking bit values, while they are stepwise changed such that the transitions of the pixel value changes are slow in the borders between the image areas and/or in the time direction, thereby producing an electronic watermarked image.