在不使用HTML表单元素的情况下将图像文件上载到服务器

我需要在服务器上上传一张图片，而不使用html表单标记。有简单的方法吗。事实上，我一直在构建一个应用程序，用户可以上传自己的照片，也可以从网络摄像头上拍摄一张新照片，如果用户点击上传按钮，照片就会移动到服务器上。当用户上传图片并按下上传按钮时，它工作得很好，因为我一直在使用类型为"文件"的HTML输入标签，但当我从网络摄像头拍摄图片并在HTML5画布标签上渲染时，我单击上传按钮，没有图片移到服务器，因为输入标签中没有文件。在这两种情况下，我都使用相同的画布元素和img标记来向用户显示它。

有没有一种方法可以在不使用表单元素的情况下上传，或者有没有一个方法可以将我从Canavas元素获得的图像对象分配到相同的表单输入元素中？？

所有答案都欢迎

提前感谢

服务器端代码

    function bytesToSize1024($bytes, $precision = 2) {
    $unit = array('B','KB','MB');
    return @round($bytes / pow(1024, ($i = floor(log($bytes, 1024)))), $precision).' '.$unit[$i];
}
$sFileName = $_FILES['image_file']['name'];
$sFileType = $_FILES['image_file']['type'];
$sFileSize = bytesToSize1024($_FILES['image_file']['size'], 1);
 $target = "upload/"; 
 $target = $target . basename( $_FILES['uploaded']['name']) ; 
 $ok=1;
$error=$_FILES["image_file"]["error"];

$uploaddir = '/var/www/example119/upload/';
$uploadfile = $uploaddir . basename($_FILES['image_file']['name']);
  if(!empty($_FILES))
  {
     if(move_uploaded_file($_FILES['image_file']['tmp_name'], "$target$sFileName")) 
     {
     echo "The file ". basename( $_FILES['image_file']['name']). " has been uploaded...";
     } 
     else {
     echo "Sorry, there was a problem uploading your file. {$error}";
     }
  }
  else
    {
    echo "_files is empty";
    }

Javascipt代码以进行HTTPrequest

function startUploading() {
    // cleanup all temp states
    iPreviousBytesLoaded = 0;
    var oProgress = document.getElementById('progress');
    oProgress.style.display = 'block';
    oProgress.style.width = '0px';
    // get form data for POSTing
    //var vFD = document.getElementById('upload_form').getFormData(); // for FF3
    var vFD = new FormData(document.getElementById('upload_form')); // this is for when user upload from browser box
    var vvFD=document.getElementById('preview1'); //added by TODO to test
    // create XMLHttpRequest object, adding few event listeners, and POSTing our data
    var oXHR = new XMLHttpRequest();        
    oXHR.upload.addEventListener('progress', uploadProgress, false);
    oXHR.addEventListener('load', uploadFinish, false);
    oXHR.addEventListener('error', uploadError, false);
    oXHR.addEventListener('abort', uploadAbort, false);
    oXHR.open('POST', 'example_upload/upload.php');
    //oXHR.send(vFD);
    oXHR.send(vvFD);
    // set inner timer
    oTimer = setInterval(doInnerUpdates, 300);
}