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watermarking with ImageMagick
You can use this
tutorial on watermarking with ImageMagick to write the shell script that does what you want. Then you will want to make a
do shell script ... AppleScript to attach to a folder action.
The thing is that JPEG is lossy so by doing the watermark with the convert (from ImageMagick) you will lose some quality. You may like to look into the droppatch for the Independant JPEG Group codebase. You can read more about droppatch, croppatch, and EXIFpatch here. If I recall correctly the Exifpatch is already included in the croppatch and droppatch candidate. The IJG homepage is here.
So what do I mean by the last paragraph? You might like to use Whew... If by watermarking you meant something like changing DCT coefficients or a spread spectrum approach, there is some nice academic literature on this (the adaptive spread spectrum techniques are neat in particular) but except for some matlab files there really is nothing out there that I know of available. If you know of anything like this, I would love to hear about it though!
Oh, two more points. Do not use Really none of this is going to do anything to seriously protect your copyright though. If you use steg to 'hide' a copyright notice, then almost any trivial image manipulation (such as recompresion) will most likely remove that. The DCT and spread spectrum watermarking techniques could be easily identified with statisical analysis. Then the infringer could use the same tools to insert his own copyright notice. Changing the JPEG comments and EXIF properties is trivial. And of course anyone with PaintShop or GIMP can crop/mask/blur your watermark in the image itself. A very determined infringer could do all this. So if you really care, why not just register all of your images that you care about with the copyright office and skip all of the watermarking that degrades the image itself. Spread spectrum or DCT coef watermarks cannot really be useful unless there is an impartial third party involved and some crypto hashes are used. But then all those watermarks can be replaced, the image can be cut-up into bits and reassembled with HTML to prevent there being enough bits of the watermark in a single part to identify, and placed behind logins so that spiders cannot see the infringing file easily, so what is the point really... |
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