Dotted line in pdf file with IE 10

问题:

The graph is the same and correct on browser, Chorme, IE11, IE10, etc....

In IE 11, I press a button to create png file, the result is correct.

In IE 10, I press a button to create png file, the result is incorrect, the dotted line of graph change to solid line.

I have no idea about this problem, can anyone help me?

IE 11:
_{(source: 2.pik.vn)}

IE 10:
_{(source: 2.pik.vn)}

This is the code i use to convert from svg to canvas:

var svg = document.getElementById("graphP").innerHTML;   
var canvas = document.getElementById("canvas");
canvg(canvas, svg);
var imgDataP = canvas.toDataURL();