Question

I have an input text field where the user provides the source url of the image ,
for example http://mysite/images/STARTPAGE_LOGO.gif is a valid value.

I dont have any img tag or something else in my html document. How can i determine the dimensions of the image which is present at the URL the user has entered .

Answer 1

There is no method to find out the width and height of the image without loading it so you will have to dynamically load it , and to do so you can use

function getDimensions(_src,_callback){
     /* create a new image , not linked anywhere in document */
     var img = document.createElement('img');
     /* set the source of the image to what u want */
     img.src=_src;
     /* Wait the image to load and when its so call the callback function */
     /* If you want the actual natural dimensions of the image use naturalWidth and natural height instead */
     img.onload = function () { _callback(img.width,img.height) };
}

After declaring the above function in pure javascript spirit you can do something like

getDimensions('http://mysite/images/STARTPAGE_LOGO.gif',function(w,h){
 console.log( "Height : ",h,"Width:",w);
});