Reading image properties in an Adobe LiveCycle Designer Form

A LiveCycle Designer form allows a user to insert a picture using an ImageField.  However, there is nothing built-in to allow access the properties of an image.  This set of script fragments makes the Exif, GPS and XMP properties of a JPEG image available.

You can also use these code fragments to determine if the image is a JPEG, GIF, PNG or TIFF.

If you just want to check the size of an image then you can use the rawValue property but as the value is base 64 encoded you will need to allow for an overhead of 33%, so ImageField1.rawValue.length * 3 / 4 will give a rough image size in bytes.

LiveCycle Designer forms allow for JPG, GIF, TIF, and PNG formats.  An ImageField allows the user to select one of these images but only if the file extension matches one of those four.  If the file extension is JPEG, JPE, or TIFF then the image will not show up in the "Select Image File" dialog.  If this is a problem for your users then you can use the importDataObject, something like;

if (event.target.importDataObject("name")) // user did not cancel the "select a data file to import" dialog
{
 var attachmentObject = event.target.getDataObject("name");
 var filetype = attachmentObject.path.substring(attachmentObject.path.lastIndexOf(".") + 1);
 if (filetype === "jpg")
 {
  var imageStream = event.target.getDataObjectContents("name");
  var imageStreamEncoded = Net.streamEncode(imageStream, "base64");
  ImageField1.rawValue = util.stringFromStream(imageStreamEncoded);
 }
}

Back to this sample, to find the date a picture was taken we can now use;

var stream = ByteStream.newByteStream(Base64.decode(ImageField1.rawValue));
var image = JPEG.newJPEG(stream);
if (image.isJPEG)
{
 app.alert(image.getDateTime());
}
else
{
 image = GIF.newGIF(stream);
 if (image.isGIF)
 {
 }
 else
 {
  image = TIFF.newTIFF(stream);
  if (image.isTIFF)
  {
  }
  else
  {
   image = PNG.newPNG(stream);
   if (image.isPNG)
   {
   }
  }
 }
}

There is a bug in the base 64 decode routines built into Adobe Reader but this has not yet proved to be a problem as it only seems to occur towards the end of the file were typically the image data is stored.  However, included in this sample is a JavaScript based base 64 decoded.  This does execute slower so I would only use it if this proves to be a problem, just change the first line to;

var stream = ByteStream.newByteStream(Base64.decode(this.rawValue));

In the sample form there are four options;

• Turn on JavaScript decoding
• Display a message if a decode error occurs
• Stop decoding when the SOF jpeg tag is found.  The only thing that may be missed is the JPEG comment tag, but this seems to be rarely used or superseded by the Exif properties.  This option should speed up the decode.
• Turn on and off displaying of the decode time.

The code in the sample form starts in the change event of the image field in the top right hand corner (with the "Click here to add photo" caption).  This loads the image and then executes the initialize event of the main ImageField to display all the image properties.  I did it this way because I am using the dataWindow object to allowing scrolling though pictures, without the dataWindow you could perform all processing in the ImageField's change event.

 The form template (without pictures of my cat) can also be downloaded, ImageViewer.xdp