While there are many ways to protect your photos from unauthorized use, watermarking still remains the simplest and probably the most effective technique that can help you to identify you as the creator and make it difficult to use your works without permission.
Although digiKam supports watermarking, this feature is hidden so well that you might not even realize that it’s there. This is because the watermarking function in digiKam is tucked under the Batch Queue Manager tool which you can use to watermark multiple photos in one go. Here is how this works in practice. Choose Tools | Batch Queue Manager (or press the B key) to open the Batch Queue Manager tool. Drag the photos you want to watermark from a digiKam album onto the Queues pane to add them to the current queue. Click on the Base Tools tab in the Batch Tools Available pane and double-click on the Add Watermark tool to add it to the Assigned Tools pane.
digiKam can use text or images as watermarks, and you can choose the desired watermark type in the Tools Setting pane. If you want to use the Image type, make sure that you already have a graphics file handy. Specify then the available settings such as Placement, Size, and Margins. Next, select the target folder in the Target section of the Queue Settings pane. In the Behavior section, you can specify what the system should do if it detects a file with the same name as the processed one in the target folder. You can either choose to overwrite the existing file or rename the processed file before saving it. You can also use the options available in the File Renaming section to specify a renaming rule to automatically rename the processed files.
Once you are satisfied with the settings, hit the Run button, and once digiKam’s finished, you’ll find the watermarked photos in the target folder.