Copyright symbol


Biological immune function provides powerful paradigms for computation which go largely untapped. This article explores one application of histocompatibility to strengthening image copyrights.

Histocompatibility Antigens

Histocompatibility is the term for antigenic differences between members of a species. It triggers transplant rejection and drives the need for blood typing in transfusions.

Although there are histocompatibility antigens encoded throughout the genome, the Major Histocompatibility Gene Complex is the source of the antigen sets prominently presented on the surface of virtually all an individual's cells.

In On the Function of MHC-Antigen Specificity Reinhold suggests that, while histocompatibility may not benefit individuals, it protects a species from extinction when a virus's proteins all mimic the hosts'.

Although cells could produce an infinite variety of MHC antigens, it would not work as well as a finite number. Detecting the absence of an antigen is not as robust as detecting all antigens in a chemically similar group except for the individual's personal set.

Copyright Transplants

Philip Greenspun's Internet Hall of Shame catalogs cases of image theft from, a corpus of photographic work. These violations amount to unauthorized tissue transplants; transplants we would like to see rejected.


Steganography, the art of hiding one piece of information within another, is sometimes proposed as a mechanism for watermarking images.

But keeping the copyright a secret does not promote compliance or enforcement. The last person to handle the image can plead ignorance of the copyright when it is invisible. If steganographic decoding software is publicly available, then it is no more protected than the plain text representation for comments currently supported by PNG, JPEG, GIF, and other image formats.

Another problem is that image compression, the art of removing all information content not visible to human viewers, is in direct conflict with the goal of steganography. Steganographic encodings must always keep pace with improvements to compressed image formats.

Presenting Histocompatibility Antigens

Like the MHC antigens, a copyright notice has a standard form containing bounded variability: the years and holder's name.

This notice should be presented in such a way that it cannot be easily removed or replaced. The copyright! program masks a portion of the image with a rectangle containing the copyright text. The mask is opaque with only the pixels underneath the letters showing through.

The mask colors are chosen to provide contrast with the pixels showing through the type. A random (Gaussian) texture is applied to the mask to foil automated recognition.

Carp image sporting a gaudy copyright!


An unmasked image is the copyright holder's certificate showing primacy. Although such an image can be forged, it will require effort by the forger; and that person cannot avoid knowing that he is tampering with a copyright in so doing.

Cropping a copyrighted image is another method of removing its notice. Although the image is not then obviously pirated, the holder's original becomes even stronger evidence of authorship. And the violator will be hard-pressed to explain how his modifications were not criminal.

Some images can be protected from cropping if the notice is pitched at 45 degrees across a corner such that cropping to eliminate it will remove significant parts of the image.

As an image is shrunk, the copyright notice will eventually be rendered unreadable, but the box containing it can remain visible to smaller scales. The copyright box should be sized so that, at the scale it disappears, so little of the original image remains that it is not worth protecting.

Biological Analogies

The whole, original image is a stem cell; many copyrighted images can be derived from it, but the derived images do not allow easy duplication under another copyright.

The copyright-branded images are like differentiated cells. They contain most, but not all of the original image information.

Steganography resembles nothing so much as a retrovirus.

The copyright box exports a small set of somewhat dispersed pixels as its histocompatibility signature. Although the pixel values can only be verified when compared with the original image, anyone viewing this copyright can compare its statement with the context where it appears.

Like MHC antigens on cell membranes, nearly every public image has a copyright, though the copyright may not appear in the image. If copyright! use becomes common, then images bearing no copyright will be suspect or rejected.


Like histocompatibility, copyright! does not provide unassailable security for any single image. But its widespread use would promote compliance and facilitate better enforcement of image copyrights.

Copyright 2002, 2003 Aubrey Jaffer

I am a guest and not a member of the MIT Computer Science and Artificial Intelligence Laboratory.  My actions and comments do not reflect in any way on MIT.
Aubrey Jaffer
Go Figure!