One of the greatest advantages of the World Wide Web is the ability to quickly and easily share information, including text, images, audio and video. This advantage can also be a tremendous disadvantage for those who wish to maintain their rights under copyright law; the ease of copying and transmitting data applies to both copyrighted and non-copyrighted materials. For digital photographs, one of the best ways to identify or protect copyrighted or original material is watermarking.
In the real world, watermarks are a method used for authenticating documents such as paper money, checks, identification cards and other important forms or papers. In the digital world, watermarking serves a similar purpose. Digital watermarks can either be visible or invisible, and can hold a virtually limitless range of different types of information, from copyright or author information to logos or information about the content of the image.
Visible watermarks are the most obvious and recognizable form of this method of protecting photos published on the Web. A visible watermark covers some portion of the image with an identifying or authenticating symbol or text, thus making the image almost impossible to copy without the origin being known. Although some software packages or algorithms are able to remove digital watermarks in images, there is almost invariably some level of distortion, since the original image information “under” the watermark is lost or changed. Although visible watermarking is, therefore, not a foolproof method of image copy protection, it does provide some level of protection. Also, the ease of adding a visible watermark to an image often makes it a palatable option.
Original image
Image with visible watermark
Invisible watermarks serve a similar function as their visible counterparts, but do not yield any noticeable distortion of the image. Invisible watermarks involve information that is incorporated into the image without producing any fundamental changes in the scene. Adding an invisible watermark to an image is often much more complicated than adding a visible watermark, although a number of available software packages perform the necessary operations automatically. If the watermarking procedure is done with sufficient care, the image can withstand significant modification, while still preserving the watermark. These watermarks can be for author identification or copyright protection, or they can be placed in the image for the purpose of preventing any doctoring of the image. In the latter case, the destruction of the watermark provides indication that the image has been altered from its original form. Such a watermarking procedure is of great interest to the news media and other institutions, where the authenticity of images is critical to maintaining integrity. In many cases, programs are available for revealing the watermarks contained in images. This can provide users with information or advertisements, as well as help to protect the image from copyright violations.
Original image
Image with invisible watermark
Author: Jeffrey Clark