Non-linear axes for imshow in matplotlib
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I am generating 2D arrays on log-spaced axes (for instance, the x pixel coordinates are generated using `logspace(log10(0.95), log10(2.08), n)`.

I want to display the image using a plain old imshow, in its native resolution and scaling (I don't need to stretch it; the data itself is already log scaled), but I want to add ticks, labels, lines that are in the correct place on the log axes.  How do I do this?

Ideally I could just use commands line `axvline(1.5)` and the line would be in the correct place (58% from the left), but if the only way is to manually translate between logscale coordinates and image coordinates, that's ok, too.

For linear axes, using `extents=` in the call to imshow does what I want, but I don't see a way to do the same thing with a log axis.