In space domain, The digital watermark of space domain superposes the watermark information on the signal space directly, Change vision alike plain values, generally in adding the watermark signal modulated in being vision the luminance or typewriter ribbons of element. 空域数字水印是直接在信号空间上叠加水印信息,从而改变图象象素的值,一般在是图象元素的亮度或色带中加入调制的水印信号。