jQuery plugin to transform every <img> source to a fpoimg url with original natural image dimensions

jquery.fpoimg.js

/*
* jQuery plugin to transform every <img> source to a fpoimg url with original
* natural image dimensions, this won't work with SVG images nor background
* images.
*
* You should instanciate this plugin before everything else that manipulate
* images.
*
* Usage exemple:
*
*     $('body').fpoimg();
*
* You may use another selector to apply this plugin on more precise container.
*
*/
(function ( $ ) {

// adds .naturalWidth() and .naturalHeight() methods to jQuery
// for retreaving a normalized naturalWidth and naturalHeight.
// Stealed from :
// http://www.jacklmoore.com/notes/naturalwidth-and-naturalheight-in-ie/
var props = ['Width', 'Height'],
    prop;
while (prop = props.pop()) {
    (function (natural, prop) {
        $.fn[natural] = (natural in new Image()) ?
        function () {
            return this[0][natural];
        } :
        function () {
            var
            node = this[0],
            img,
            value;

            if (node.tagName.toLowerCase() === 'img') {
                img = new Image();
                img.src = node.src,
                value = img[prop];
            }
            return value;
        };
    }('natural' + prop, prop.toLowerCase()));
};

// Shortcut for String.endswith behavior
function endsWith(str, suffix) {
    return str.indexOf(suffix, str.length - suffix.length) !== -1;
}

/*
* Plugin extensions calling logic
*/
$.fn.fpoimg = function(method) {
    // Specific public method called
    if ( extensions[method] ) {
        return extensions[method].apply( this, Array.prototype.slice.call( arguments, 1 ));
    // Default public method to init the plugin
    } else if ( typeof method === 'object' || ! method ) {
        return extensions.init.apply( this, arguments );
    // Unknow called method
    } else {
        $.error( 'Method ' +  method + ' does not exist on jQuery.fpoimg' );
    }
};

/*
* Plugin extension methods
*/
var extensions = {
    /*
    * Initialize plugin, default public method, must be called first
    */
    init : function(options) {
        return this.each(function() {
            var $this = $(this);
            //
            // Attempt to fpoimg'ize every image
            $('img').each(function() {
                var $image = $(this),
                    width = $image.naturalWidth(),
                    height = $image.naturalHeight(),
                    url = $image.attr('src'),
                    newurl;

                // Dont proceed on SVG images since their original cant be
                // easily retrieved
                if(url && !endsWith(url, '.svg')){
                    //console.log("%s: %s x %s", url, width, height);
                    // Build fpoimg url
                    newurl = "http://fpoimg.com/" + width + "x" + height;
                    //console.log("To: %s", newurl);
                    $image.attr('src', newurl);
                    $image.attr('data-fpoimg-original', url);
                }
            });
        });
    }
};

}( jQuery ));