On Sat, 2004-09-18 at 19:24, Tim Hunter wrote:
> Daniel Cremer wrote:
> 
> > Hi,
> > 
> > Are there any libraries for ruby that do invisible watermarking on
> > images ? If not, does anyone know of a good C library that could be
> > ported to ruby.
> > thanks,
> > -Daniel
> 
> RMagick (http://rmagick.rubyforge.org) includes a `stegano' method, which
> can be used to embed a watermark in an image. It's uses are quite limited,
> however. Only lossless RGB format images, such as PNG images, can be
> watermarked. The stegano method does not work with GIF (pseudocolor), or
> JPEG (lossy) images. Once watermarked, the image cannot be edited in any
> way or the watermark will be destroyed.
> 
> AFAIK, "industrial strength" steganography, such as that offered by
> Digimark, is expensive and commonly uses patented techniques.
> 
> 

Thank you. Yes my problem is that I would like to use it on JPEGs. The
most important for me is not to have things encrypted or resist editing
but to just have an ID and a tiny amount of meta-data encoded into the
actual jpeg so that it can identified even if the filename changes.