Watermark is a mark or lettering over the photo showing its owner: a photographer or a website. Here are a couple of watermark samples:
Visual Watermark Blog (English) - page 16
Aperture is photo management software for Mac that allows you to store and refine high volumes of photos. All images are stored in a special folder called library. This means when importing photos from a camera memory card Aperture copies them into an internal storage (“library”). You can easily erase your memory card while Aperture will store original photos for you on your hard disc.
However, this makes photo watermarking a bit inconvenient since Visual Watermark cannot retrieve images from the library, only Aperture can. You should export your photos from the library first. This tutorial shows how this can be done.
78% percents of US photographers say their photos were being used illegally. Most likely your photos were stolen too. Can it be possible to find who is using your images? Now there is an answer. Google started an image reverse search service that uses image identification technology to find exact matches of the photo you ask it to search for. It’s as easy as dragging and dropping your photo into the search box.
Visual Watermark is a image watermarking tool for Mac and Windows. Since Mac-version is a much newer program, it lacks some features existing in the Window-version. One of them is the capability to add your own logotype stored as an image file.
These are standard methods to add a trademark symbol to any program on your computer. They are built-in into your operating system and available in every program you have: Word, Picasa, Visual Watermark and all others.