During the Wiki Loves Monuments 2012 photgraphy contest we received quite a few of photos containing watermarks or signatures, which is pretty dumb considering the images are licensed freely (Creative Commons Attribution Share Alike) and they are intended for Wikipedia use, such a watermark will make them less usefull and the free license will allow editors do clean them. Let me quote from Wikimedia Commons why is a bad idea to watermark your uploads:
- Watermarks can be unfree, if they feature a logo or any copyrighted image.
- They may contain copyright statements, which affect the reuseability of the image.
- They detract from the quality of images
- They can negatively influence the neutrality of images, or be considered advertising, and cannot be used on certain projects
- Images with watermarks are far less likely to be used
- Watermarks will be, in most cases, removed anyway by image editors - uploading a watermarked version only creates a lot of extra work for other volunteers
But Wikipedia is an inclusive project, your contributions are accepted, even if defective, with watermarks making them less useful. Of course, you do it on your own risk, they won't be nominated as quality images and won't receive any prize. You may get contacted by an editor, asking for a clean verion, you can help or not.
If you are an editor wanting to clean such pictures, Wikipedia also has some help for you, but this help is geared more to Photoshop users, with the GIMP part focusing more on loseless JPEG editing than watermark cleaning. If the cleaning is bad, the loseless part is less important, methinks, so this is why I will show here a few GIMP techniques. I am using for demonstration real files, submitted by a participant, Antonius Plaian in the Romanian Wiki Loves Monuments 2012 contest.Crop
The easiest way to remove an unwanted part of the image is by cropping it, of course, this will work only if the watermark/signature does not cover an important part of the image, like this Raibow over Timișoara:
There are downsizes to cropping, some (hopefully unimportant) data is lost and the composition is afected, the image won't look as intended any more. Is simple and sometime may work.
However, if cropping does not work, we can use more advanced techniques.