Can't reduce margin during image print

[riadapsis]

Thanks for the great plugin. Now I am facing the following problem while printing image-

• Want to use full width of paper (58mm). But there is a margin at both side and can't remove it.
  
  Please help. I am stuck for last couple of days. Sample code:

var c = document.getElementById("canvas");
var ctx = c.getContext("2d");
ctx.clearRect(0, 0, c.width, c.height);
ctx.fillText("প্রতি প্যাকেটের মূল্য:",0,25);
ctx.fillText('BKH:20s-২০১.৯০,12s-১২১;',0,50);
ctx.fillText('LPGL/PM/CAP:20s-১৩৯.৯০',0,75);
ctx.fillText("KPML:12s-৮৩.৯৪;SRR:20s৮৯.৯০;",0,100);
ctx.fillText("DBBL/BBL:20s-৫৩.৯০, 10s ২৬.৯৫",0,125);
var imageData = canvas.toDataURL('image/png');
BTPrinter.printImage(function (data3) {
	}, function (err) {
		alert("ERRO IMAGEM"+ JSON.stringify(err));
	}, imageData);