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Haven't tried it out but from a quick inspection, this looks like it might be suitable: https://github.com/NaturalIntelligence/imglab

VGG Image Annotator

https://gitlab.com/vgg/via/

Its not open source but this tool helps in managing labeling by your in-house team or contractual workers. It also provides you annotation software for most of image and text usecases. Here is link to the same.

http://dataturks.com

thanks ! but we would prefer something that had open source availability (the gitlab model) as a fallback measure.

im seeing labelbox and i think they follow that - https://www.labelbox.com/

Check out https://pybossa.com/