HTML5 canvas background image repeat

Question

I have a html5 canvas that draws a sound wave. I have set the background as an background image, however, I want this background image to repeat. Can anyone tell me how I would do this and what I need to add into my code:

var backgroundImage = new Image(); 
backgroundImage.src = 'http://www.samskirrow.com/client-kyra/images/main-bg.jpg'; 
var canvas;
var context;

function init(c) {
    canvas = document.getElementById(c);
    context = canvas.getContext("2d");
    soundManager.onready(function() {
        initSound(clientID, playlistUrl);
    });
    aniloop();
}

function aniloop() {
    requestAnimFrame(aniloop);
    drawWave();
}

function drawWave() {

    var step = 10;
    var scale = 60;

    // clear
    context.drawImage(backgroundImage, 0, 0);

    // left wave
    context.beginPath();
    context.moveTo(0, 256);
    for ( var i = 0; i < 256; i++) {
        context.lineTo(6 * i, 257 + waveLeft[i] * 80.);
    }
    context.lineWidth = 1;
    context.strokeStyle = "#000";
    context.stroke();

    // right wave
    context.beginPath();
    context.moveTo(0, 256);
    for ( var i = 0; i < 256; i++) {
        context.lineTo(6 * i, 256 + waveRight[i] * 80.);
    }
    context.lineWidth = 1;
    context.strokeStyle = "#000";
    context.stroke();
}

function updateWave(sound) {
    waveLeft = sound.waveformData.left;
}

return {
    init : init
};
})();

You can see this code in action here: http://www.samskirrow.com/client-kyra

Answer 1

Use the canvas' createPattern function

var canvas = document.getElementById("canvas"),
    context = canvas.getContext("2d"),
    img = new Image();

img.src = 'https://www.google.nl/images/srpr/logo3w.png';

img.onload = function(){
    // create pattern
    var ptrn = context.createPattern(img, 'repeat'); // Create a pattern with this image, and set it to "repeat".
    context.fillStyle = ptrn;
    context.fillRect(0, 0, canvas.width, canvas.height); // context.fillRect(x, y, width, height);
}

<canvas id="canvas" width="600px" height="600px"></canvas>

(This is the fastest of the 2 samples).

Or, try a manual implementation:

var canvas = document.getElementById("canvas"),
    context = canvas.getContext("2d"),
    img = new Image();

img.src = 'https://www.google.nl/images/srpr/logo3w.png';

img.onload = function(){
    for (var w = 0; w < canvas.width; w += img.width) {
        for (var h = 0; h < canvas.height; h  += img.height) {
            context.drawImage(img, w, h);
        }
    }
}

<canvas id="canvas" width="600px" height="600px"></canvas>