I think what the Anonymous Monk is asking here is not to prevent the image from being saved, but to prevent the underlying drawing file from being saved. CAD files are very complex beasts (object databases really) and for many reasons one may want to allow others to view or print them without getting at the underlying structure, and without being able to alter it.

There is a simple solution for what you want, and it comes from no stranger a source than Autodesk. For some years now there has been a special format for AutoCAD drawings called Drawing Web Format (DWF) which was designed especially for what you're talking about. On the downside it requires the viewer to have the (free) WHIP! plugin, but that provides a huge range of viewing features that could be helpful to your application.

On the cheaper end of things, I know of companies that only send JPGs of their drawings over the web. This works fairly well when the images are simple and don't change often, but you can imagine that the applications are limited. Municipalities like this approach to serving things like property maps which are very simple and rarely change.

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I'd like to be able to assign to an luser