Hello to all!

I know, this question was asked before, but as Mars opposition
approaches, there might be a solution on that already.

Today I got a BIG mail from a fellow which contained a truly gigantic
zylindrical projection of the Mars surface, about 21000 x 11000 pixel
in dimension - which is exactly 1km per pixel in resolution. He could
not tell where this was from, perhaps JPL.

I would like to convert this image into something useful for Guide.

What I really want to avoid is resending the monster per mail, since
this image is just over 100MB. The file format is lossless(!) JPEG
which reproduces every pixel like the original and does not introduce
compression artifacts.

Best Regards