Adobe 13102498 User Guide - Page 477

PHOTOSHOP CS3 470 User Guide Adding digital copyright information You can add copyright information to Photoshop images and notify users that an image is copyright protected via a digital watermark that uses Digimarc ImageBridge technology. The watermark-a digital code added as noise to the image-is virtually imperceptible to the human eye. The Digimarc watermark is durable in both digital and printed forms, surviving typical image edits and file format conversions. Embedding a digital watermark in an image lets viewers obtain information about the creator of the image. This feature is particularly valuable to image creators who license their work to others. Copying an image with an embedded watermark also copies the watermark and any information associated with it. For more detailed information on embedding Digimarc digital watermarks, refer to the Digimarc website at www.digimarc.com. Before adding a digital watermark Keep in mind the following considerations before embedding a digital watermark in your image. Color variation The image must contain some degree of variation or randomness in color to embed the digital watermark effectively and imperceptibly. The image cannot consist mostly or entirely of a single flat color. Pixel dimensions The Digimarc technology requires a minimum number of pixels to work. Digimarc recommends the following minimum pixel dimensions for the image to be watermarked: • 100 pixels by 100 pixels if you don't expect the image to be modified or compressed prior to its actual use. • 256 pixels by 256 pixels if you expect the image to be cropped, rotated, compressed, or otherwise modified after watermarking. • 750 pixels by 750 pixels if you expect the image to appear ultimately in printed form at 300 dpi or greater. There is no upper limit on pixel dimensions for watermarking. File compression In general, a Digimarc watermark will survive lossy compression methods, such as JPEG, though it is advisable to favor image quality over file size (a JPEG compression setting of 4 or higher works best). In addition, the higher the Watermark Durability setting you choose when embedding the watermark, the better the chances that the digital watermark will survive compression. Workflow Digital watermarking should be one of the very last tasks you perform on an image, except for file compression. Use the following recommended workflow: • Make all necessary modifications to your image until you are satisfied with its final appearance (this includes resizing and color correction). • Embed the Digimarc watermark. • If needed, compress the image by saving it in JPEG or GIF format. • If the image is intended for printed output, perform the color separation. • Read the watermark and use the signal strength meter to verify that the image contains a watermark of sufficient strength for your purposes. • Publish the digital watermarked image. See also "Using the Watermark Durability setting" on page 471