How to create custom COCO data set for object detection | DLology blog
Then you can run the voc2coco.py script to generate a COCO data formatted JSON file for you.
python voc2coco.py ./data/VOC/Annotations ./data/coco/output.json
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.