[chestervonwinch]

> isn't the majority of modern object recognition, segmentation, etc. done with convnets?

Not at all. Big networks might be popular within particular groups, and they have certainly achieved impressive results on a number of tasks recently, but it's not the solution to every problem. There are a number of other approaches - just browse over the number of subsections on image segmentation on wiki, for example:

https://en.wikipedia.org/wiki/Image_segmentation

or, perhaps more appropriately, take a look at the methods used in recent papers on image segementation:

https://scholar.google.com/scholar?as_ylo=2016&q=%22image+se...