javascript - save image with ajax in ruby on rails -

i dont know how save image in ajax ruby on rails, repo in github, github.com/luis77/editor22 please chek out, have been trying 2 days, dont know wrong. example, check view attachment/new here code in javascript ajax code:

 <script>     var canvas = document.createelement('canvas');     var context = canvas.getcontext('2d');     var centerx = canvas.width / 2;     var centery = canvas.height / 2;     var radius = 70;      context.beginpath();     context.arc(centerx, centery, radius, 0, 2 * math.pi, false);     context.fillstyle = 'green';     context.fill();     context.linewidth = 5;     context.strokestyle = '#003300';     context.stroke();      document.body.appendchild(canvas)       var dataurl =  canvas.todataurl('image/png');        // convert dataurl blob object       function dataurltoblob(dataurl) {     // decode dataurl         var binary = atob(dataurl.split(',')[1]);     // create 8-bit unsigned array     var array = [];     for(var = 0; < binary.length; i++) {         array.push(binary.charcodeat(i));        }     // return our blob object     return new blob([new uint8array(array)], {type: 'image/png'});       }            // our file       var file= dataurltoblob(dataurl);       // create new form data       var fd = new formdata();      // append our canvas image file form data       fd.append("image", file);       // , send       $.ajax({          url: "/attachments/change2",          type: "post",          data: fd,          processdata: false,          contenttype: false,       });         </script> 

it's specified in routes:

  post "attachments/change2" 

and method in controller,

but won't save, need code, please help.

assuming javascript code correct, , post data making server correctly, use carrierwave or paperclip handle file uploads.