How to parse this json file and write separate sub object as json files?

[panovr]

My json file like:

[
    {
        "annotations": [
            {
                "class": "bbox",
                "height": 457.0,
                "id": "001",
                "type": "rect",
                "width": 336.0,
                "x": 97.0,
                "y": 60.0
            },
            {
                "class": "head",
                "height": 114.0,
                "id": "001",
                "type": "rect",
                "width": 208.0,
                "x": 222.0,
                "y": 65.0
            },
        ],
        "class": "image",
        "filename": "001.jpg"
    },
   {
        "annotations": [
            {
                "class": "bbox",
                "height": 406.0,
                "id": "001",
                "type": "rect",
                "width": 311.0,
                "x": 108.0,
                "y": 147.0
            },
            {
                "class": "head",
                "height": 107.0,
                "id": "001",
                "type": "rect",
                "width": 187.0,
                "x": 113.0,
                "y": 152.0
            },
        ],
        "class": "image",
        "filename": "002.jpg"
    },
]

You can see its document root is an Array object, and there are 2 separate objects in it. Now I want to create separate Document with every object as root, and write these Documents as separate json files. How can I achieve this?
Thanks!

[panovr]

just use the these codes for reading and writing:

// read a JSON file
std::ifstream i("file.json");
json j;
i >> j;

// write prettified JSON to another file
std::ofstream o("pretty.json");
o << std::setw(4) << j << std::endl;

The API is designed well, and easy to use.
Thanks for sharing this project!