The present invention provides an image watermarking technique whereby a watermark is inserted into an adjusted digital source image that is bounded by a specific bounding rectangle. If the source image is larger than the rectangle, its dimensions are reduced by a common factor until it is the largest adjusted image that lies totally within the rectangle. A watermark is inserted into the adjusted image and at least one derived image of larger or smaller size is produced. Then, regardless of the size of an image derived from the watermarked adjusted image, enlarging or reducing that image to again lie within the rectangle greatly facilitates detection of the imbedded watermark. The size of the bounding rectangle may be specific to each source image, or, conversely, a common bounding rectangle may be used for a group of source images.