JPEG compression stable digital watermarking method and system based on picture content

The invention discloses a JPEG compression stable digital watermarking method and system based on picture content. The method is brought forward based on some constant properties in a sub process of discrete cosine transform in picture JPEG compression, for instance, high orders of DC components are constant and embedded water marks can maintain absolute stability under certain pure color conditions, the property that the high orders of the DC components are constant can help to ensure that extracted original picture features after a watermark is embedded can maintain constant, the property that embedded watermark information maintains stable under the certain pure color conditions can help to ensure that information of the watermark itself is absolutely stable. The method comprises two portions, i.e., a watermark information embedding portion, and a portion of extracting the watermark information and detecting whether a picture is modified. According to the method and system, all detail information of an ori