Commons:Blur

Usually we want images on Commons to be clear (sharply focused, little or no motion blur). However, there are times when we have good reason to blur part of an image, usually with a Gaussian blur, which does a very good job of preserving the look of the scene when rendered at lower resolution, while effectively presenting "zooming in" on certain elements.

Why we would want to blur an image

Each of the paintings on the wall in the background of this image was "covered" with a Gaussian blur. At low resolutions, the picture "reads" almost exactly as it would without the blur, but if you zoom in the pictures are sufficiently indistinct that we believe their inclusion in the picture qualifies as de minimis.

Typically, we would want to blur part of an image to make that portion of the image less distinct. Reasons for this would include:

• Obscure a copyrighted object within the image.
• Hide identifying information (e.g. a face, a license plate, etc.).
• Remove distracting background artifacts. E.g. we might have a good picture of a notable person, but someone else in the background is sufficiently in focus to be distracting. We might want to blur the latter person.

A very weak Gaussian blur can also be a useful technique to "smooth" an image that has a significant number of pixel-level artifacts.

Process

A blur is typically applied outside of Commons, using an image processing tool such as GIMP or Adobe Photoshop. While it is possible (and can be desirable) for an uploader to selectively blur an image before uploading, another common sequence is:

• Uploader uploads an image that (for example) has an element in it that is copyrighted and above the de minimis threshold, or shows identifying information that, for one or another reason, either the uploader or community consensus considers inappropriate for Commons.
• Someone notices the problem, often via a DR.
• Someone (often a third party) downloads the full-resolution version of the image, blurs the offending portion with an image processing tool, and overwrites the original image.
  • When doing this upload, you should typically add Category:Gaussian blurs as concealment or other similar category to the file page of the image.
• An administrator hides the original upload. Ideally, this last is done by changing the visibility only of the actual file content, while keeping the Edit summary and the Editor's username/IP address for the prior upload. (That is, it is less desirable to delete the earlier version outright.)

Other techniques of concealment

The Seattle underground paper Helix never gave a copyright notice as was required to obtain copyright in the U.S. in its era, but occasionally reprinted a particular cartoon, advertisement, etc. that had its own valid copyright notice. Rather than just blur such an element here, we have replaced it entirely, substituting text that explains why it was removed and when it will pass into the public domain and the original scan can be restored.

Sometimes we wish to more completely remove a copyrighted element from an image. This is particularly applicable to copies of printed documents, such as a newspaper that may be in the public domain but contains an advertisement or cartoon that is still copyrighted. In that case, the procedure is similar, but rather than a blur, we typically substitute a solid-color area, often adding text to the image itself to explain the substitution (example at right). Again, this should be placed in some subcategory of Category:Censored images, typically Category:Images with blanked out components.