Avoid zooming in HTML5 canvas

[Nitin Daphale]

When I draw on my HTML5 canvas, it is zoomed already? Hence drawn arrow below is blurred! (snap attched).
What is the Reason?
Any help to avoid this?

var ctx = document.getElementById("canvasWhiteboard").getContext("2d");
ctx.beginPath();
ctx.moveTo(touchX, touchY);
ctx.lineTo(moveX, moveY);
ctx.lineWidth = 4;
ctx.strokeStyle = "black";
ctx.stroke();