canvas 이미지를 서버에 저장하는 방법

function posting() {

  const canvas = document.getElementById('canvas');
  const imgBase64 = canvas.toDataURL('image/jpeg', 'image/octet-stream');
  const decodImg = atob(imgBase64.split(',')[1]);

  let array = [];
  for (let i = 0; i < decodImg .length; i++) {
    array.push(decodImg .charCodeAt(i));
  }

  const file = new Blob([new Uint8Array(array)], {type: 'image/jpeg'});
  const fileName = 'canvas_img_' + new Date().getMilliseconds() + '.jpg';
  let formData = new FormData();
  formData.append('file_give', file, fileName);

    $.ajax({
      type: "POST",
      url: "/fileupload",
      data: formData,
      cache: false,
      contentType: false,
      processData: false,
      success: function (response) {
        alert(response["result"])
        window.location.href = '/result'
      }
    });
  }