html - Convert from img URL to file to send via ajax to server -

i want take image url entered text box user , save file server.

so far i've saved files users this...

var myformdata; document.getelementbyid("fileinput").onchange = function () {        myformdata = new formdata();       myformdata.append('uploadfile', $("#fileinput").prop('files')[0]);        $.ajax({           url: '/php/uploadfile.php',            type: 'post',           processdata: false,            contenttype: false,            datatype : 'text',           data: myformdata,            success: function(response){           },           error: function(response){           }         });     } }; 

but of course works when user chooses via input of type="file", , i've learned other posts security reasons it's impossible programatically set value of $("#fileinput").prop('files')[0].

so seems achieve need way convert img have (e.g. http://www.imageexamples.com/image1.jpg) file can append form , upload via ajax. sound correct way go? if so, i've been struggling find examples of others doing it, appreciate pointers @ all!

sop prevent downloading images arbitrary websites ajax.
should send url server , let server download , store image.