"Copyright" isn’t a concept that means much online, and we’re not just talking about the latest movies: put your own photos on the web and people will be reusing them in no time at all.
GFXMark Free is a versatile Windows application which can protect your copyright with a range of image watermarking tricks.
There’s support for a good set of watermark types, including text and images, single and tiled, or just plain diagonal lines.
Each of these is very customizable. You’re able to choose your preferred font, color, opacity, watermark position, rotation, number and style of diagonal lines, and more.
GFXMark Free’s most unusual feature is its "brightness-aware" technology, where in theory the program automatically adjusts the watermark color and opacity for maximum visibility (text will be dark on a light background, or light when it’s dark).
This isn’t quite as simple as it sounds -- you may need to adjust brightness thresholds, perhaps set new light/ dark colors, and even then the results aren’t guaranteed for every image -- but even accepting the default settings will usually improve your results.
Bonus features include options to draw a border around your image, and add custom EXIF copyright tags, as well as uploading the images to Facebook when you’re done.
The Free build of GFXMark does have significant restrictions. It only accepts 10 images per operation; there’s a maximum export resolution of 1200 x 800; it’s for personal use only.
If you can live with that, GFXMark Free’s configurability and brightness-aware watermarking makes it worth a try.
Alternatively, the excellent ImBatch provides capable and unrestricted image watermarking -- along with about 100 other picture processing tasks -- for no charge at all.
GFXMark Free is a free-for-personal-use application for Windows XP and later.