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When I write letters that need to be sent via snail mail, I print them out and sign them manually. In the case of letters that can be sent via e-mail, I add an image of my signature using includegraphics.

In such a letter, it’s possible to right-click the image and save it, but I would rather that were not possible. Can it be made impossible or at least difficult?

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  • You can right click and extract an image from a PDF? I'm surprised, which pdf viewer are you using? Mar 5 '20 at 9:19
  • Usually mupdf, but I tried it in evince. It works.
    – Philipp
    Mar 5 '20 at 9:19
  • wow, it is true that now is possible, ... but try with a pdf image (a draw from inkscape with some layers saved as pdf) and you will see ...
    – Fran
    Mar 5 '20 at 9:33
  • @Fran Can you explain what I should do with the existing png image I have? I open it in inkscape, and then? Simply save as pdf? When I use the newly created pdf as image instead of the png, it is as extractable as the png
    – Philipp
    Mar 5 '20 at 9:44
  • Maybe you can prevent this specific way of storing the image (although I doubt it), but you cannot prevent screenshots.
    – Marijn
    Mar 5 '20 at 9:56
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You can add scanned PNG image of the signature to Inkscape, vectorize it, then remove PNG image, save the draw as PDF and use it as image in the LaTeX file. Then the menus to save the image disappear. Using the signature as a layer on top of a PNG image, the option to save the image will available again, but only to save the PNG background, simulating some anti-copy mechanism. A trasparent PNG of top of the vectorized also will work in thi sense.

Moreover, making some small modification of the signature (for instance, a very very tiny text inside some trace, invisible without a huge zoom) the screenshot will not reproduce exactly the signature, so it can be checked easily that is not the original, as it will be pixelated after some zoom. However, it can be extracted unaltered with Inkscape, so there are not secure methods, except use also a digital signature.

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