Canvas image fade

HTML

<h1>Original</h1>

<canvas id="original"></canvas>

<h1>Partially Transparent</h1>

<canvas id="partial"></canvas>

<h1>Attempted Fade</h1>

<canvas id="fade"></canvas>

CSS

canvas {
    display: block;
}

JavaScript

var sourceImage, ctx, originalCanvas, partialCanvas, fadeCanvas, partialCtx, fadeCtx;

//get the canvases
originalCanvas = document.getElementById('original');
partialCanvas = document.getElementById('partial');
fadeCanvas = document.getElementById('fade');


//get the google logo
sourceImage = new Image();

sourceImage.src =...