[Solved]-Blank PNG image using Chart JS . toBase64Image() function-Chart.js

you have to call save64img(mychart.tobase64image()) over an additional callback. you can add this callback to the options

lineoptions = {
    onanimationcomplete: function () {
       save64img(mychart.tobase64image());
    }
}

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();
}