Canvas element with blurred lines

Question

I wonder why the edges/lines of my canvas element are blurred (Chrome, IE, FF) and have a so-called "sawtooth-effect" (does this expression exist in english? :-)) as you can see here:

It is just a quick first try - maybe I did something wrong? Here is the code:

c2 = document.getElementById('test').getContext('2d');
c2.fillStyle = '#f00';
c2.beginPath();
c2.moveTo(0, 0);
c2.lineTo(100, 0);
c2.lineTo(80, 50);
c2.lineTo(0, 50);
c2.closePath();
c2.fill();

c2.fillStyle = "#000";
c2.beginPath();
c2.moveTo(0, 50);
c2.lineTo(80, 50);
c2.lineTo(60, 100);
c2.lineTo(0, 100);
c2.closePath();
c2.fill();

I also added it to this JS Fiddle

Answer 1

You can oversample the canvas (fake double resolution):

Here's an illustration with standard resolution on top and "double" resolution on bottom:

A Demo: http://jsfiddle.net/m1erickson/M5NHN/

Html:

<canvas id="canvas1" width=300 height=150></canvas>
<canvas id="canvas2" width=600 height=300></canvas>

CSS:

#canvas1 {
    border:1px solid red;
    width:300px;
    height:150px;
}
#canvas2 {
    border:1px solid green;
    width:300px;
    height:150px;
}

JS:

var canvas = document.getElementById("canvas1");
var context1 = canvas.getContext("2d");
var canvas = document.getElementById("canvas2");
var context2 = canvas.getContext("2d");

draw(context1);

context2.scale(2, 2);
draw(context2);

function draw(c2){

c2.fillStyle = '#f00';
c2.beginPath();
c2.moveTo(0, 0);
c2.lineTo(100, 0);
c2.lineTo(80, 50);
c2.lineTo(0, 50);
c2.closePath();
c2.fill();

c2.fillStyle = "#000";
c2.beginPath();
c2.moveTo(0, 50);
c2.lineTo(80, 50);
c2.lineTo(60, 100);
c2.lineTo(0, 100);
c2.closePath();
c2.fill();
}