Chartjs convert toBase64 not working in an iframe - image

Question

I have a problem when i am trying to generate the Base64 of my chartjs line.
The console.log of my base64 string is : "data:," (attachment)
i am launching this code in an iframe, not in the parent page. On this chart, there are 30000 lines of data.
**When i directly launched the page, i have no problem, everything is OK.
**
Here is my code :
`
function generateTrend2(data){
var line = document.getElementById('chartContainer').getContext('2d')
var dataY = []
var dataX = []
data.forEach(function (item) {
dataY.push(item.y)
dataX.push(item.x)
})
var lineChart = new Chart(line, {
type: 'line',
data: {
labels: dataX,
datasets: [{
data: dataY,
label: "Sample Coverage",
borderColor: "#3e95cd",
fill: false,
borderWidth: 1
}]
},
options: {
animation: {
duration: 0,
},
hover: {
animationDuration: 0,
},
responsiveAnimationDuration: 0,
onAnimationComplete: done(),
elements: {
point:{
radius: 0
}
}
}
});
function done(){
setTimeout(function(){
var image = lineChart.toBase64Image();
console.log(image)
$("body").append("<input type='hidden' value='" + image + "' id='img-chart' >")
},1000)
}
}
`
I tried to put a delay of 200,500,1000,5000,10000, but the result is the same in my var image...
I have generated an other base64 with an other chart with similar code, the same system, in an iframe and i have no problem.