Get actual dimension of image. Using jQuery.

gistfile1.js

/**
 * 画像の実際のサイズを取得する
 *
 * @param  string  image  img要素
 */
function getActualDimension(image) {
     var run, mem, w, h, key = "actual";
     // for Firefox, Safari, Google Chrome
     if ("naturalWidth" in image) {
          return {width: image.naturalWidth, height: image.naturalHeight};
     }
     if ("src" in image) { // HTMLImageElement
          if (image[key] && image[key].src === image.src) {return  image[key];}

          if (document.uniqueID) { // for IE
               w = $(image).css("width");
               h = $(image).css("height");
          } else { // for Opera and Other
               mem = {w: image.width, h: image.height}; // keep current style
               $(this).removeAttr("width").removeAttr("height").css({width:"",  height:""});    // Remove attributes in case img-element has set width  and height (for webkit browsers)
               w = image.width;
               h = image.height;
               image.width  = mem.w; // restore
               image.height = mem.h;
          }
          return image[key] = {width: w, height: h, src: image.src}; // bond
     }

     // HTMLCanvasElement
     return {width: image.width, height: image.height};
}