Barcode is widely used to enter information from paper, screen, and others with a mobile phone or smartphone. This means that information on photos can be considered even after its printing. There are many programs for mobile phones or smart phones to read 2D barcodes. If the barcode will contain a link to your site, then it is possible to increase traffic to your site.
Because the barcode can be used as a watermark, your copyright will be protected regardless of where your photo is placed: in the Internet or on paper.
Example of barcode is shown in the following figure.