Of course, the degree to which such images are re-usable is subject to interpretation, creativity, and hard work. However, the file size needed for reproducing the same image at same scale for offset printing say, for use in a brochure or book would require a resolution of at least 266 dpi, a constraint that would considerably reduce the final size of the printed image. Watermarking Watermarked images offer a higher degree of protection for images that are of sufficient resolution to be potentially abused. They can be applied to static web images as well as material released for review or reproduction. Various commercial systems are available that allow some form of encoded identifier to permanently accompany an image and verify its source.
Watermarks can either be visible or invisible.
These embed a semi-ghosted visual logo across the image, making commercial use impractical. It allows for an image or text to be overlaid onto a main image as a visible watermark at variable levels of transparency and can accommodate batch processing. Invisible watermarks are more common in public information settings such as digital libraries and galleries. The encryption involved in embedding the unique code in the image is robust enough to survive even after resizing, cropping, and other graphic torture. It is important to note that watermarks cannot prevent the theft of an image, but they can be extremely valuable for tracking abuse and proving ownership once it has happened.