Reading Embedded XMP Packets using ColdFusion

Fri, 20 Feb 2009 12:29:00 -0500

In working more and more on our Digital Asset Management initiatives, I've become more involved in working with XMP. Mostly as an experiment, I wanted to see if I could read and write this embedded metadata from and to a file. The Adobe XMP Toolkit indicates how this can be done based on the structure of specific types of files. It also indicates that packet scanning techniques can be used when file structure is unknown, however, is not encouraged.

I recognize it might not be the BEST way to read the XMP packet, however, all is fair in love and ColdFusion experimentation :) It's important to note that this code looks only for the FIRST instance of the string <x:xmpmeta and if there are multiple instances of XMP packets, subsequent instances are ignored. Adobe also indicates that if there are multiple packets, there is no way to know which packet is the correct one.

Needless to say, using the code below, I was able to read and parse XMP packets from all the Adobe sample files included in their toolkit. It may not be the end-all solution, and may not work for writing back to the file, but it's a start!

<cfparam name="URL.source" default="xmp-asset.jpg">
<cffile action="readbinary" file="#ExpandPath(URL.source)#" variable="data">

<cfset hex_data = BinaryEncode(data,"hex") />

<cfset xmp_string_begin = "3C783A786D706D657461" />

<cfset xmp_string_end = "3C2F783A786D706D6574613E" />

<cfset idx_start = FindNoCase(xmp_string_begin,hex_data) />

<cfset idx_end = FindNoCase(xmp_string_end,hex_data,idx_start) + Len(xmp_string_end) />

<cfset xmp_hex = Mid(hex_data,idx_start,Evaluate(idx_end-idx_start)) />

<cfset xmp_string = ToString(BinaryDecode(xmp_hex,"hex")) />

<cfset xmp_xml = XmlParse(xmp_string) />
<cfcontent type="text/xml">
<cfoutput>#xmp_string#</cfoutput>

Be sure to check out the Adobe XMP Developer Center for more information.

GenuineJD - XMP

Reading Embedded XMP Packets using ColdFusion