Question

I’m working on a drawing application with HTML5 (canvas) which works fine besides that what you draw gets kind of “jagged” and not as smooth as I want it to be. Below is the code; what can be the problem here?

$(function() {
    var letsdraw = false;

    var theCanvas = document.getElementById('paint');
    var ctx = theCanvas.getContext('2d');
    theCanvas.width = 420;
    theCanvas.height = 300;

    var canvasOffset = $('#paint').offset();

    $('#paint').mousemove(function(e) {
        if (letsdraw === true) {
            ctx.lineTo(e.pageX - canvasOffset.left, e.pageY - canvasOffset.top);
            ctx.stroke();
        }
    });

    $('#paint').mousedown(function() {
        letsdraw = true;
        ctx.strokeStyle = 'blue';
        ctx.lineWidth = 10;
        ctx.lineCap = 'round';
        ctx.beginPath();
        ctx.moveTo(e.pageX - canvasOffset.left, e.pageY - canvasOffset.top);
    });

    $(window).mouseup(function() {
        letsdraw = false;
    });
});

Answer 1

Using shadowBlur you can make it look better. See this : http://jsfiddle.net/diode/EsYqm/6/ . You have to adjust the blur settings with lineWidth.

But for a perfect solution, you will have to develop an algorithm for smoothing line, like this http://courses.engr.illinois.edu/ece390/archive/archive-f2000/mp/mp4/anti.html