Capture Maps Backend API

This API captures detailed images of an area using Google Maps Static API

This API is intended to be consumed by Capture Maps UI. However, it is may be consumed by other systems as is.

Setup

1. Create configs/config.toml in the project root and store Google Maps Static API

   cd configs/; cp config.toml.template config.toml

2. Run project

   go run src/main.go

Docker Dev

Set GOOGLE_MAPS_API_KEY in deploy/docker-compose.yml

cd deploy
docker compose up --build -d

Docker Dev

Set GOOGLE_MAPS_API_KEY in deploy/docker-compose.prod.yml

cd deploy
docker compose -f docker-compose.prod.yml up -d

Sample request

POST /print
Content-Type: application/json

{
    "lat": 30.316963, 
    "lng": 78.032560,
    "zoom": 15,
    "radius": 5
}

Sample Response

Access-Control-Allow-Origin: *
Content-Type: image/png
Transfer-Encoding: chunked

What about the watermark? According to Google Maps Platform Terms of Service, the branding, logos, and copyright and trademark notices can not be removed. :'(

How does it work?

1. Latitude and longitudes are converted to Google maps tile coordinates (the first tile is the centre)
2. The specification (the level of details and area it covers) is defined by the combination of zoom, scale , and pixels (scale and pixels are internally configured)
3. The tiles coordinate around the center tile is calculated using the radius. The radius is number of tiles from the center tile (inclusive)
4. The tiles are then joined together and to construct a single detailed image
5. Then do the same north and south to the center row

For example, the centre row of the complete grid consists individual tiles collected from west to east with length 2 * radius - 1

c1	c2	c3	c4	c5	c6	c7	c8	c9

After stitching the tiles we get the centre row