rotate.html

<canvas width=300 height=300 style="display:none"></canvas>

<h4>Original</h4>
<img class="original" src="https://dl.dropboxusercontent.com/u/139992952/stackoverflow/house-icon.png">
    
<h4>90 graus</h4>
<img class="rotate90">
    
<h4>180 graus</h4>
<img class="rotate180">

rotate.js

var imgOriginal = document.querySelector('.original').src;

var canvas=document.querySelector("canvas");
var ctx=canvas.getContext("2d");

var image=document.createElement("img");
image.src=imgOriginal;

function drawRotated(degrees){
    ctx.clearRect(0,0,canvas.width,canvas.height);
    ctx.save();
    ctx.translate(canvas.width/2,canvas.height/2);
    ctx.rotate(degrees*Math.PI/180);
    ctx.drawImage(image,-image.width/2,-image.width/2);
    ctx.restore();
    return canvas.toDataURL("image/png").replace("image/png", "image/octet-stream");
}

document.querySelector('.rotate90').src = drawRotated(90);