I’ve seen this used before to add a credit that only appears when you save the image. You append the credit to the bottom of the image, then crop the image with

I’ve seen this used before to add a credit that only appears when you save the image. You append the credit to the bottom of the image, then crop the image with CSS using a technique like this to hide the credit. Then when somebody saves the image, they get the whole thing and the credit appears.