matplotlib/matplotlib — pull request #1090 by pelson (2012-08-15 12:19:52+00:00)
Title: External transform api

This PR adds an easy interface for matplotlib transform creation based on a custom object.

The syntax looks like:

```
class MyObject(object):
_as_mpl_transform(self, axes):
return ... # a matplotlib transform instance
```

This interface is comprable to the ```_as_mpl_axes``` method to easily create axes from custom classes.

My primary usecase for both of these cases is to provide an interface which could do something like:

```
plate_carree = MyProjectionLibrary.PlateCarree()
robinson = MyProjectionLibrary.Robinson()

ax = plt.axes(projection=robinson)
plt.plot(lons, lats, transform=plate_carree)
```