Jpeg

thoand

I know this is not a PHP question,
but does anyone know how to calculate the filesize of an JPEG image.

I have this Javascript, where I get the values from two textfields (width and height)

and resize the image on the fly (onKeyPress)

It would be nice to get the filesize before submitting.

acording to JPEG I guess I need to know at least this:

width
height
JPEG quality

but I dont know how to do the math,
please anyone help

thanks in advance,
regards Thomas A.

nightowl

guess it depends on the picture too and that a 'calculation' is not possible. I can imagine a complete white picture to be smaller than a complex one ...

Don't know javascript enough, but can't you count the 'length' of the var you will be submitting ? This may give you the filesize or an approximation...

stolzyboy

found this out there, you may have to rework some of it to suit your needs, but it does the trick...

<HTML>
<HEAD>
<SCRIPT>
function getImageDimension (imgURL, loadHandler) {
  var img = new Image();
  img.onload = loadHandler;
  if (document.layers 
      && location.protocol.toLowerCase() != 'file:' 
      && navigator.javaEnabled())
    netscape.security.PrivilegeManager.enablePrivilege(
      'UniversalFileRead'
    );
  img.src = imgURL;
}
function getFileSize (fileName) {
  if (document.layers) {
    if (navigator.javaEnabled()) {
      var file = new java.io.File(fileName);
      if (location.protocol.toLowerCase() != 'file:')
        netscape.security.PrivilegeManager.enablePrivilege(
        'UniversalFileRead'
        );
      return file.length();
    }
    else return -1;
  }
  else if (document.all) {
    window.oldOnError = window.onerror;
    window.onerror = function (err) {
      if (err.indexOf('utomation') != -1) {
        alert('file access not possible');
        return true;
      }
      else 
        return false;
    };
    var fso = new ActiveXObject('Scripting.FileSystemObject');
    var file = fso.GetFile(fileName);
    window.onerror = window.oldOnError;
    return file.Size;
  }
}
function showImageDimensions () {
  alert(this.width + 'x' + this.height);
}
</SCRIPT>
<SCRIPT>
function checkImageDimensions (fileName) {
  var imgURL = 'file:///' + fileName;
  getImageDimension(imgURL, showImageDimensions);
}
</SCRIPT>
</HEAD>
<BODY>
<FORM NAME="formName">
<INPUT TYPE="file" NAME="fileName">
<BR>
<INPUT TYPE="button" VALUE="check file size"
       ONCLICK="alert(getFileSize(this.form.fileName.value))"

<BR>
<INPUT TYPE="button" VALUE="check image dimensions"
       ONCLICK="checkImageDimensions(this.form.fileName.value)"

</FORM>
</BODY>
</HTML>