[Chartjs]-Extension for chart.js 2.X

With 2.1.x, you can write a plugin to do this

Preview

Script

Chart.pluginService.register({
    afterDraw: function (chart) {
        if (chart.config.options.elements.center) {
            var helpers = Chart.helpers;
            var centerX = (chart.chartArea.left + chart.chartArea.right) / 2;
            var centerY = (chart.chartArea.top + chart.chartArea.bottom) / 2;

            var ctx = chart.chart.ctx;
            ctx.save();
            var fontSize = helpers.getValueOrDefault(chart.config.options.elements.center.fontSize, Chart.defaults.global.defaultFontSize);
            var fontStyle = helpers.getValueOrDefault(chart.config.options.elements.center.fontStyle, Chart.defaults.global.defaultFontStyle);
            var fontFamily = helpers.getValueOrDefault(chart.config.options.elements.center.fontFamily, Chart.defaults.global.defaultFontFamily);
            var font = helpers.fontString(fontSize, fontStyle, fontFamily);
            ctx.font = font;
            ctx.fillStyle = helpers.getValueOrDefault(chart.config.options.elements.center.fontColor, Chart.defaults.global.defaultFontColor);
            ctx.textAlign = 'center';
            ctx.textBaseline = 'middle';
            ctx.fillText(chart.config.options.elements.center.text, centerX, centerY);
            ctx.restore();
        }
    },
})

and then

    ...
    options: {
        elements: {
            center: {
                text: 'Hello',
                fontColor: '#000',
                fontFamily: "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif",
                fontSize: 24,
                fontStyle: 'normal'
            }
        }
    }
};

Fiddle – http://jsfiddle.net/a1r1kszb/