Project a disk to a plane...

[jumpjack]

I have this image:
http://photojournal.jpl.nasa.gov/jpeg/PIA19932.jpg

I want to convert it into mercator projection; of course it will be just half the width of a full mercator projection, as it's just one emisphere, but it's ok for me.

How do I do that?

[snibgo]

IM doesn't have built-in operations for map projections.

You need to know the input projection. It might be rectlinear (like a photograph taken from an infinite distance).

Then you need a bit of maths to convert from rectilinear to mercator. Fortunately, many people have done this. A quick Google turns up this one: http://www.users.globalnet.co.uk/~arcus/mmps/

[fmw42]

Imagemagick does not have a distort method to deal directly with Mercator (or any other such cartographic projections) Projections. You could implement the mathematics of the Mercator projection with the IM -fx function, but it would be extremely slow.

The closest thing in IM is a depolar transform. See http://www.imagemagick.org/Usage/distorts/#polar