The present invention relates to an image processing apparatus and device intended to temporally modulate a sequence of source images with a modulation image comprising at least one anti-copy pattern. According to the invention, it is proposed that the modulation image be generated on the basis of the source image to be modulated in such a way as to place the patterns at locations of the image that may hinder the person watching an illicit copy of the video sequence (filmed for example by a camcorder). The modulation image is for example an image of the secondary contours of the image. The patterns are therefore placed in the low-gradient zones of the source image.