toDataURL() gives checkered background to downloaded chart

Hi im trying to save save image of chart. Im using Angular12, Chart.js for drawing charts. When I download it with toDataUrl() background in image is checkered[ https://i.stack.imgur.com/WYmBf.png ]

here is my code in ts file

public barChartLabels: Label[] = ['Pon', 'Uto', 'Sri', 'Cet', 'Pet', 'Sub', 'Ned'];
  public barChartType: ChartType = 'bar';
  public barChartLegend = true;
  public barChartPlugins = [];
  public colors: Colors[] = [
    {
      backgroundColor:     
        'rgb(0, 102, 255)'
      
    }
  ];

  public barChartData: ChartDataSets[] = [
    { data: [], label: 'Series A' }
  ];
  data1: Array<number> =[0, 0, 0, 0, 0, 0, 0]
  


Skini(){
  //var image = document.getElementById("voznje")!.toBase64Image();
  var canvas : any = document.getElementById("voznje");
  var ctx = canvas.getContext("2d");
  //var image = ctx.toDataURL("image/jpeg");
  var dataURL = canvas.toDataURL("image/png", 1.0);
  console.log(dataURL)
  var link = document.createElement('a');
  link.download = "my-chart.png";
  link.href = dataURL;
  link.click();
  //window.open(dataURL);
    //console.log("Link",dataURL)
  
}

and this is in html

  <canvas id="voznje"
        style="background-color: white"
         baseChart 
          [datasets]="barChartData"
          [labels]="barChartLabels"
          [options]="barChartOptions"
          [plugins]="barChartPlugins"
          [legend]="barChartLegend"
          [chartType]="barChartType"
          [colors]="colors">
        </canvas>

I would like to have normal backgound. Thank you in advance

Solved it. Code now looks like this. Like person in comment said i needed to give color to canvas background.

Skini(){
  //var image = document.getElementById("voznje")!.toBase64Image();
  var canvas : any = document.getElementById("voznje");
  var ctx = canvas.getContext("2d");
  //var image = ctx.toDataURL("image/jpeg");
  ctx.globalCompositeOperation = 'destination-over'
  ctx.fillStyle = "white";
  ctx.fillRect(0, 0, canvas.width, canvas.height);
  var dataURL = canvas.toDataURL("image/png", 1.0);
  //console.log(dataURL)
  var link = document.createElement('a');
  link.download = "my-chart.png";
  link.href = dataURL;
  link.click();
  //window.open(dataURL);
    //console.log("Link",dataURL)
  
}