We used Sloth for segmentation labelling (polygons instead of pixels). Direct pixel labelling is very expensive, so usually you can save lots of time by simplif

We used Sloth for segmentation labelling (polygons instead of pixels). Direct pixel labelling is very expensive, so usually you can save lots of time by simplifying the problem - one of them being polygon labelling. Although Sloth is a gtk app it was the best option available year ago - much better than free web based options available back then. We packaged it into single windows exe that we were distributing to labellers in a zip alongside data to label. Labellers would send back zip + annotated data in json format custom to Sloth. Zips landed in s3 folder and we had some scripts doing analytics on that (e.g. Labellers reliability). It was very easy to extend and add new functions to sloth. Although it seems low tech comparing to web labelling it took us surprisingly lots of work to beat this workflow with web based purpose-built workflow.