I think there are several tutorials out there on drawing cabriole legs but they aren't terribly difficult to do. Basically you draw the front elevation and the side elevation and extrude them through each other. Then intersect the extrusions and delete the waste. The rounding of the front corner is a little more involved but you could create a path for Follow Me from the corner resulting from the intersection or you could create horizontal sections, round the corners of those sections and then use the Skin plugin to make the faces.
I would be inclined to draw these legs from scratch because I expect you'd work harder modifying a typical cab leg to make it look like the ones on the chair.
Have you already had an opportunity to take measurements? Do you have ready access to the chair?
It looks like a very nice piece.
Dave