Embroidering it is no different from any other design.
As for digitising it, it all depends on your software. In Husqvarna 3D PictureStitch for instance you have only little control over the process, the whole picture is digitised at once - of course you set certain variables, but that's it.
In Embird's Sfumato on the other hand the process is a bit like digitising a normal design: you set the points around each area of your picture and have much greater influence on the outcome, which I prefer.