Clipping path?

Here's a bit of the gm manpage (this option would apply to the mogrify
and convert subcommands, at least).

 -clip  apply the clipping path, if one is present

        If a clipping path is present, it will be applied to subsequent operations.

        For example, if you type the following command:

             gm convert -clip -negate cockatoo.tif negated.tif

        only the pixels within the clipping path are negated.

        The  -clip  feature  requires the XML library.  If the XML library is not present, the
        option is ignored.

But but but ...

First, what is the "XML library", how do I know if it is present and
where do I get it if not present?

Second, what kind of thing is the clipping path?  A file - what file?
Environment variable?  Or what?  What information should be inside the
thing and in what format?

I suspect this bit has been mindlessly (or automatically) copy-pasted
from the API docs without considering the specific situation of the
command-line tool user.

-- 
Ian Zimmerman
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fingerprint: 66DC D68F 5C1B 4D71 2EE5  BD03 8A00 786C C6FF 61AD
Rule 420: All persons more than eight miles high to leave the court.

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