Render a retrieved image using a blob: URL

HTML

<img id="photo"/>

CSS

body {
    /* Add a background so white image will show up. */
    background: gray;
}

JavaScript

// Simulate a call to Dropbox or other service that can
// return an image as an ArrayBuffer.
var xhr = new XMLHttpRequest();

// Use JSFiddle logo as a sample image to avoid complicating
// this example with cross-domain issues.
xhr.open( "GET", "https://fiddle.jshell.net/img/logo.png", true );

// Ask for the result as an ArrayBuffer.
xhr.responseType = "blob";

xhr.onload = function( e ) {
    var blob = this.response;
    var reader = new FileReader();
    reader.onload = function() {
    	var dataURL = reader.result;
      document.querySelector('#photo').src = dataURL;
    }
    reader.readAsDataURL(blob);
};

xhr.send();