This repo is a simple set of python scripts to convert the Imagenet database to a COCO-style .json database. It was written around the ILSVRC2014 dataset, and may not work exactly for other years of the dataset.
There is also code provided that will split the database by a synset node. For example, you can create two databases, one that has all animal images associated, and one with only non-animal images.
Examples of the resulting files can be seen in the ILSVRC2014 folder