An image containing text (e.g., a surveillance camera photo that includes a vehicle license plate) is analyzed to determine the text (e.g., by an OCR technique). The recognized text is then stored in a database. The image is digitally watermarked with an identifier that associates the image with the database location where the text is stored. In addition to surveillance contexts, this technology can be employed in indexing the World Wide Web. Images used in web pages can be watermarked to link to associated text or other data. When the web page is crawled by an indexer, the watermark can be decoded and the associated data repository accessed to obtain information that can augment the web index for that page.