A Morning Glory 'Kniola's Black' that is. The flower is actually a lot DARKER than the image shows. The camera just doesn't do purple very well. It's a very dark purple and you can barely see those darker lines. Ipomoea purpurea 'Kniola's Black' ( photo / image / picture from FlowerFreak22's Garden )
I have some that were grown from seed. I'm hardening them off now ready for planting into the garden. Mine are sky blue though not the rich colour yours are.