This repository contains a Node.js application that starts a server which can render ECharts graphs to PNG images.
This application needs two prerequisites:
- Node.js (preferably the latest LTS version)
- PhantomJS (installed via NPM)
The installation of Node.js is covered in a separate document.
(If you prefer a setup within a Docker container over a native installation, then please take a look at Setup with Docker.)
The application requires a package for PhantomJS. To install that, type
npm install
in the directory export-server/. You only need to do this once. The packages
are then cached in the node_modules/ directory for future use.
However, PhantomJS does not offer a prebuilt package for some platforms, namely ARM which is used by Raspberry Pi (among others). In such case you can install the PhantomJS package provided by your package manager via
apt-get install phantomjs
on Raspbian, or via
yum install phantomjs
on RedHat-based distributions.
You can simply start the application via
npm start
which fires up the Node.js application. The server will then listen on http://localhost:3000/ for incoming connections.
To generate a PNG file of an ECharts plot, just send an HTTP POST request to the running Node.js server on http://localhost:3000/ containing the data for the plot as JSON in its body.
For example, POSTing the following JSON code to the server
{
"imageHeight":400,
"imageWidth":1000,
"title": {
"text": "ECharts entry example"
},
"tooltip": {},
"legend": {
"data": ["Sales"]
},
"xAxis": {
"data": ["shirt","cardigan","chiffon shirt","pants","heels","socks"]
},
"yAxis": {},
"series": [{
"name": "Sales",
"type": "bar",
"data": [5,20,36,10,10,20]
}]
}
will generate a JSON response like e.g.:
{
"success": true,
"filename": "graph-1520685763528.png"
}
The field filename in the response indicates the location of the generated image file on the server. In the example above you could then get the image from http://localhost:3000/graph-1520685763528.png. Given the data above the image would look like this:
If you encounter problems while trying to generate a chart image, then please take a look at the FAQ. Some common errors and possible solutions are listed there.
Copyright 2018, 2020 Dirk Stolle
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.