Converting Chart.js canvas chart to image using .toDataUrl() results in blank image

Question

I am using Chart.js. I am trying to convert the chart to an image by getting a base 64 string. The tutorial (http://www.chartjs.org/docs/) devotes an entire 1 line on the to

Answer 1

You should use the Chartjs API function toBase64Image() instead and call it after the animation is complete. Therefore:

var pieChart, URI;

var options = {
    animation : {
        onComplete : function(){    
            URI = pieChart.toBase64Image();
        }
    }
};

var content = {
    type: 'pie', //whatever, not relevant for this example
    data: {
        datasets: dataset //whatever, not relevant for this example
    },
    options: options        
};    

pieChart = new Chart(pieChart, content);

Example

You can check this example and run it

var chart = new Chart(ctx, {
   type: 'bar',
   data: {
      labels: ['Standing costs', 'Running costs'], // responsible for how many bars are gonna show on the chart
      // create 12 datasets, since we have 12 items
      // data[0] = labels[0] (data for first bar - 'Standing costs') | data[1] = labels[1] (data for second bar - 'Running costs')
      // put 0, if there is no data for the particular bar
      datasets: [{
         label: 'Washing and cleaning',
         data: [0, 8],
         backgroundColor: '#22aa99'
      }, {
         label: 'Traffic tickets',
         data: [0, 2],
         backgroundColor: '#994499'
      }, {
         label: 'Tolls',
         data: [0, 1],
         backgroundColor: '#316395'
      }, {
         label: 'Parking',
         data: [5, 2],
         backgroundColor: '#b82e2e'
      }, {
         label: 'Car tax',
         data: [0, 1],
         backgroundColor: '#66aa00'
      }, {
         label: 'Repairs and improvements',
         data: [0, 2],
         backgroundColor: '#dd4477'
      }, {
         label: 'Maintenance',
         data: [6, 1],
         backgroundColor: '#0099c6'
      }, {
         label: 'Inspection',
         data: [0, 2],
         backgroundColor: '#990099'
      }, {
         label: 'Loan interest',
         data: [0, 3],
         backgroundColor: '#109618'
      }, {
         label: 'Depreciation of the vehicle',
         data: [0, 2],
         backgroundColor: '#109618'
      }, {
         label: 'Fuel',
         data: [0, 1],
         backgroundColor: '#dc3912'
      }, {
         label: 'Insurance and Breakdown cover',
         data: [4, 0],
         backgroundColor: '#3366cc'
      }]
   },
   options: {
      responsive: false,
      legend: {
         position: 'right' // place legend on the right side of chart
      },
      scales: {
         xAxes: [{
            stacked: true // this should be set to make the bars stacked
         }],
         yAxes: [{
            stacked: true // this also..
         }]
      },
      animation : {
         onComplete : done
      }      
   }
});

function done(){
    alert(chart.toBase64Image());
}