Any chance you'd consider supporting the Kavrayskiy VII, Eckert IV or Winkel-Tripel projections? It looks like PROJ.4 supports those projections.
Eckert III (Winkel Tripel) and IV are possible, but not Kavrayskiy since proj4 doesn't do the inverse.
However, both look very similar to the Robinson. What's your use case?
The Winkel (and Kavrayskiy 7) seem to be regarded as projections with the least distortion and the Eckert 4 seems to be regarded as the best area-preserving projection, at least by this professor . Though this researcher finds the Robinson to be better. (I'm not a cartographer, so I'm not sure). I'm mainly looking at different ways to visualize global data contours, and examining different map projections.
OK - but unless you have a real pressing need for adding those, I can't justify spending the time on it. Of course, patches are welcome.
Fair enough, I'll send a patch your way if I find time to implement them. Thanks!
It turned out to be very easy to add - the 'eck4' and 'kav7' projections are now in my fork (https://github.com/jswhit/basemap). Please let me know if they work as expected, and then I will merge them into the master.
'kav7' and 'eck4' now added to master