Map Legend Image Generator

Generate a legend image for a map from a json configuration.

This was developed to generate static legend images for some layers on EAHW as an alternative to generating directly with HTML.

Sample Output

Sample output

Dependencies

The Legend Image Generator service is built using Go and can be executed either natively or using Docker, each of which has its own set of requirements.

Native execution requires:

• Go

Execution using Docker requires:

• Docker
• Docker Compose

Getting started

Start by cloning the repository from github to your execution environment

git clone https://github.com/icpac-igad/legend-image-generator.git && cd legend-image-generator

After that, follow one of the instructions below:

Using native execution

1 - Install go dependencies using go:

go get

2 - Start the application server:

go run main.go

The endpoints provided by this microservice should now be available on http:localhost:9000

Only the root endpoint is currently exposed i.e /

Using Docker

1 - Create and complete your .env. You can find an example .env.sample file in the project root.

2 - Build the the image

docker-compose build

3 - Run the container

docker-compose up

Environment variables

• PORT => Target TCP port in which the service will run
• RESTART_POLICY => Docker container restart policy. You will want this set to always in production

usage

The / endpoint only accepts POST requests with a json payload that should look like below:

{
    "legend_type": "discrete",
    "width": 600,
    "item_height": 30,
    "label_size": 20,
    "label_space": 26,
    "transparent": true,
    "items": [
        {
            "color": "#b4b4b4",
            "value": "10%"
        },
        {
            "color": "#BB3426",
            "value": "20%"
        },
        {
            "color": "#D44F24",
            "value": "30%"
        },
        {
            "color": "#EF7424",
            "value": "40%"
        },
        {
            "color": "#FFA229",
            "value": "50%"
        },
        {
            "color": "#FFBD2D",
            "value": "60%"
        },
        {
            "color": "#FFD931",
            "value": "70%"
        },
        {
            "color": "#FFF636",
            "value": "80%"
        },
        {
            "color": "#C6FF35",
            "value": "90%"
        },
        {
            "color": "#75FF32",
            "value": "100%"
        }
    ]
}

• legend_type - string - The type of legend you wish to generate. Currently not implemented. We have it here for future addition of other legends types.
• items - list - a list of key value pairs of the legend items. The required keys are :
  • color - string - the hex color
  • value - string - the legend item label
• transparent - boolean - Set true to generate the image with a transparent background. White background by default
• width - int - width of the legend. If not provided, 500 is used by default
• item_height - int - height of the color bar. 20 by default
• label_size -int - font size of the labes. 12 by default
• label_space - int - space between color bars and labels. 5 by default.

This sample configuration will give you an output similar to the example shown above.

Adjust the configuration as necessary to achieve the desired legend images.