Using NodeJS in conjunction with ChartJS, I am able to render graphs directly to a file successfully.
This is achieved by installing the npm module ChartjsNodeCanvas.
To display labels on the graph, I utilize the official ChartJS plugin ChartJS-plugin-datalabels
However, it seems like the Canvas module has a different way of activating ChartJS plugins and it is likely that I am not activating the datalabels plugin correctly. As a result, the labels are not being displayed on the graph.
const Chart = require('chart.js');
const datalabels = require('chartjs-plugin-datalabels')
const { CanvasRenderService } = require('chartjs-node-canvas');
const width = 600;
const height = 400;
const chartCallback = (ChartJS) => {
ChartJS.defaults.global.elements.rectangle.borderWidth = 2;
ChartJS.plugins.register({
datalabels
});
};
const canvasRenderService = new CanvasRenderService(width, height, chartCallback);
(async () => {
const configuration = {
type: 'bar',
data: {
datasets: [
{
type: "bar",
barThickness: 24,
label: 'My dataset',
data: ydata['data'],
backgroundColor: 'rgba(75,192, 192, 0.2)',
borderColor: 'rgba(54, 162, 135, 0.2)',
borderWidth: 1,
datalabels: {
align: 'start',
anchor: 'start'
}
},
labels: xdata,
}
options: {
scales: {
yAxes: [
{
id: 'left-y-axis',
position: 'left',
stacked: false,
ticks: {
beginAtZero: true,
callback: (value) => value + "R"
},
},
{
id: 'right-y-axis',
position: 'right'
}
],
xAxes: [{
stacked: true,
}]
},
plugins: {
datalabels: {
backgroundColor: function(context) {
return context.dataset.backgroundColor;
},
borderRadius: 4,
color: 'red',
font: {
weight: 'bold'
},
formatter: Math.round
}
}
}
};
const image = await canvasRenderService.renderToBuffer(configuration);
fs.writeFileSync(tgMsgPath+"test.png", image)
})();
The chart is displayed but unfortunately no labels appear on the graph.