Blank PNG image using Chart JS . toBase64Image() function

Question

I am attempting to save a copy of my chart created using Chart.JS graphing libraries. When I am using the .toBase64Image() function to display or save the .png image I am getting a blank image. I have tried displaying in an img tag and saving the image with PHP. save64Img is my function to display/save the image. Has anyone had any luck using this feature?

lineOptions = {
        scaleShowGridLines : true,
        scaleGridLineColor : "rgba(0,0,0,.05)",
        scaleGridLineWidth : 1,
        bezierCurve : false,
        pointDot : true,
        pointDotRadius : 4,
        pointDotStrokeWidth : 1,
        pointHitDetectionRadius : 20,
        datasetStroke : true,
        datasetStrokeWidth : 1,
        datasetFill : true,
        responsive: true,      
        scaleOverride : true,
        scaleSteps : 5,
        scaleStepWidth : 20,
        scaleStartValue : 0

    }

    lineChart = {
            labels : label,
            datasets : [
                {
                    label: "stat1",
                    fillColor : "rgba(128,0,0,0.2)",
                    strokeColor : "rgba(128,0,0,1)",
                    pointColor : "rgba(128,0,0,1)",
                    pointStrokeColor : "#fff",
                    pointHighlightFill : "#fff",
                    pointHighlightStroke : "rgba(128,0,0,1)",
                    data : stat1
                },
                {
                    label: "stat2",
                    fillColor : "rgba(151,187,205,0.2)",
                    strokeColor : "rgba(151,187,205,1)",
                    pointColor : "rgba(151,187,205,1)",
                    pointStrokeColor : "#fff",
                    pointHighlightFill : "#fff",
                    pointHighlightStroke : "rgba(151,187,205,1)",
                    data : stat2
                }
            ]

    };

var myChart = new Chart(ctx).Line(lineChart, lineOptions);

save64Img(myChart.toBase64Image());

----------

<?php 
$data = base64_decode(preg_replace('#^data:image/\w+;base64,#i', '', $img));

file_put_contents('/tmp/image.png', $data);

?>

Answer 1

I know that it's been awhile since you have asked the question, but in the Chart.js v2 you have to use onComplete method within the animation option.

animation: {
    duration: 1500,
    onComplete: function (animation) { 
        this.toBase64Image();
}