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.
digiKam supports watermarking. The watermarking function in digiKam is available under the Batch Queue Manager tool which you can use to watermark multiple photos in one go. 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 Control Panel pane and double-click on the Decorate/Add Watermark tool to add it to the Assigned Tools pane.
digiKam can use Text or Image as watermarks, and you can choose the desired watermark type at the top of the Tool Settings pane with the Watermark type option. Check Use Absolute Size option if you want the watermark to use the given size of the font or the image without any adjustment to the actual image.
If you want to use the Image watermark type, make sure that you already have a graphics file handy, and select it from the file system. Check Ignore Watermark aspect Ratio option if you want the watermark to ignore its own aspect ratio and use the image's aspect ratio instead. Check Add transparency to watermark image if you want watermark to be transparent and tune the Opacity value in percentages with the option just below.
The Text watermark is more simple to use as it does not require an external source of contents to generate the mark over the images. In Watermark text field, enter the desired string to use superimposed contents. Below, you can tune the Font properties to write text on images, as the name, the style, and the color (the size is auto-calculated). With Text opacity you can adjust the transparency of the watermark text, where 100 is fully opaque and 0 is fully transparent. Finally, the Use background allows to draw the text over a colored background where you can choose the color and the transparency level.
Specify in this view the watermark geometry settings such as Placement Position, Rotation, Size, and Margins.
Placement Type is the lead geometry setting which will enable or disable other options from this view. Specific Location allows to set a static position of the watermark. Systematic Repetition will place the watermark in loop to cover the images. Random Repetition will place the watermark randomly over the images.
Density of watermark repetition is Disabled in Specific Location mode. When you choose to have the watermark repeated many times in the Placement Type, you can specify here whether the repetition.
Randomize watermark orientation is enabled in Random Repetition mode only. When you choose to have the watermark repeated randomly in the Placement Type, you can specify here to randomly rotate the watermark (0, 90, 180, 270 degrees).
Use Sparsity Factor option to get more control over the sparsity of watermark repetition. The higher the value the sparser the watermarks get. Use floating point values, typically between 1.0 and 3.0. It can also be less than 1.0.
Placement Position allows to specify the area on the image to write the watermark. Available values are Top left, Top right, Bottom left, Bottom right, Center, Top center, and Bottom center.
Rotation allows to specify the amount of degrees to rotate the watermark. Available values are 0 degrees, 90 degrees CW, 180 degrees, and 270 degrees CW.
Size setting allows to specify the size of watermark, as a percentage of the marked image.
X margin and Y margin allow to specify the margin from the edge in X and Y directions, as a percentage of the marked image.
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. See below the samples of text and image watermarks applied to the same image using transparency.