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...
Some time back I read about some software in Nasa Tech Briefs that
was
used to fix distorted images. It worked very well. So I bet if you
serached the magazine you could find it. I don't remember if it was
developed by NASA or if it was available to the general public for
free. You should check.
Eric

You would need a reference model to measure the distortion from, like
an image of a grid.

I attended a lecture by the engineer in charge of correcting the
second order spherical aberration in the Hubble's mirror. They knew
exactly what the problem was and could partly correct images based on
the fact that stars are point sources. The final fixes however were
compensating optics on replacement instruments rather than software.

-jsw