How to create custom COCO data set for instance segmentation | DLology blog
Then you can run the labelme2coco.py script to generate a COCO data formatted JSON file for you.
python labelme2coco.py images
Then you can run the following Jupyter notebook to visualize the coco annotations. COCO_Image_Viewer.ipynb
Further instruction on how to create your own datasets, read the tutorial.