xmp.php

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<?php

/******************************************************************************
*
* Filename:     XMP.php
*
* Description:  Provides functions for reading and writing information to/from
*               the 'App 1' Extensible Metadata Platform (XMP) segment of JPEG
*               format files. This XMP segment is XML based and contains the
*               Resource Description Framework (RDF) data, which itself can
*               contain the Dublin Core Metadata Initiative (DCMI) information.
*
* Author:       Evan Hunter
*
* Date:         27/7/2004
*
* Project:      JPEG Metadata
*
* Revision:     1.10
*
* Changes:      1.00 -> 1.04 : changed put_IPTC to fix a bug preventing the correct
*               insertion of a XMP block where none existed previously
*
*               1.04 -> 1.10 : changed put_XMP_text to fix some array indexes which were missing qoutes
*
* URL:          http://electronics.ozhiker.com
*
* Copyright:    Copyright Evan Hunter 2004
*
* License:      This file is part of the PHP JPEG Metadata Toolkit.
*
*               The PHP JPEG Metadata Toolkit is free software; you can
*               redistribute it and/or modify it under the terms of the
*               GNU General Public License as published by the Free Software
*               Foundation; either version 2 of the License, or (at your
*               option) any later version.
*
*               The PHP JPEG Metadata Toolkit is distributed in the hope
*               that it will be useful, but WITHOUT ANY WARRANTY; without
*               even the implied warranty of MERCHANTABILITY or FITNESS
*               FOR A PARTICULAR PURPOSE.  See the GNU General Public License
*               for more details.
*
*               You should have received a copy of the GNU General Public
*               License along with the PHP JPEG Metadata Toolkit; if not,
*               write to the Free Software Foundation, Inc., 59 Temple
*               Place, Suite 330, Boston, MA  02111-1307  USA
*
*               If you require a different license for commercial or other
*               purposes, please contact the author: [e-mail]
*
******************************************************************************/

include_once 'XML.php';





/******************************************************************************
*
* Function:     get_XMP_text
*
* Description:  Retrieves the Extensible Metadata Platform (XMP) information
*               from an App1 JPEG segment and returns the raw XML text as a
*               string. This includes the Resource Description Framework (RDF)
*               information and may include Dublin Core Metadata Initiative (DCMI)
*               information. Uses information supplied by the get_jpeg_header_data
*               function
*
* Parameters:   jpeg_header_data - a JPEG header data array in the same format
*                                  as from get_jpeg_header_data
*
* Returns:      xmp_data - the string of raw XML text
*               FALSE - if an APP 1 XMP segment could not be found,
*                       or if an error occured
*
******************************************************************************/

function get_XMP_text( $jpeg_header_data )
{
        //Cycle through the header segments
        for( $i = 0; $i < count( $jpeg_header_data ); $i++ )
        {
                // If we find an APP1 header,
                if ( strcmp ( $jpeg_header_data[$i]['SegName'], "APP1" ) == 0 )
                {
                        // And if it has the Adobe XMP/RDF label (http://ns.adobe.com/xap/1.0/\x00) ,
                        if( strncmp ( $jpeg_header_data[$i]['SegData'], "http://ns.adobe.com/xap/1.0/\x00", 29) == 0 )
                        {
                                // Found a XMP/RDF block
                                // Return the XMP text
                                $xmp_data = substr ( $jpeg_header_data[$i]['SegData'], 29 );

                                return $xmp_data;
                        }
                }
        }
        return FALSE;
}

/******************************************************************************
* End of Function:     get_XMP_text
******************************************************************************/






/******************************************************************************
*
* Function:     put_XMP_text
*
* Description:  Adds or modifies the Extensible Metadata Platform (XMP) information
*               in an App1 JPEG segment. If a XMP segment already exists, it is
*               replaced, otherwise a new one is inserted, using the supplied data.
*               Uses information supplied by the get_jpeg_header_data function
*
* Parameters:   jpeg_header_data - a JPEG header data array in the same format
*                                  as from get_jpeg_header_data
*               newXMP - a string containing the XMP text to be stored in the XMP
*                        segment. Should be constructed using the write_XMP_array_to_text
*                        function
*
* Returns:      jpeg_header_data - the JPEG header data array with the
*                                  XMP segment added.
*               FALSE - if an error occured
*
******************************************************************************/

function put_XMP_text( $jpeg_header_data, $newXMP )
{
        //Cycle through the header segments
        for( $i = 0; $i < count( $jpeg_header_data ); $i++ )
        {
                // If we find an APP1 header,
                if ( strcmp ( $jpeg_header_data[$i]['SegName'], "APP1" ) == 0 )
                {
                        // And if it has the Adobe XMP/RDF label (http://ns.adobe.com/xap/1.0/\x00) ,
                        if( strncmp ( $jpeg_header_data[$i]['SegData'], "http://ns.adobe.com/xap/1.0/\x00", 29) == 0 )
                        {
                                // Found a preexisting XMP/RDF block - Replace it with the new one and return.
                                $jpeg_header_data[$i]['SegData'] = "http://ns.adobe.com/xap/1.0/\x00" . $newXMP;
                                return $jpeg_header_data;
                        }
                }
        }

        // No pre-existing XMP/RDF found - insert a new one after any pre-existing APP0 or APP1 blocks
        // Change: changed to initialise $i properly as of revision 1.04
        $i = 0;
        // Loop until a block is found that isn't an APP0 or APP1
        while ( ( $jpeg_header_data[$i]['SegName'] == "APP0" ) || ( $jpeg_header_data[$i]['SegName'] == "APP1" ) )
        {
                $i++;
        }



        // Insert a new XMP/RDF APP1 segment at the specified point.
        // Change: changed to properly construct array element as of revision 1.04 - requires two array statements not one, requires insertion at $i, not $i - 1
        array_splice($jpeg_header_data, $i, 0, array( array(       "SegType" => 0xE1,
                                                                        "SegName" => "APP1",
                                                                        "SegDesc" => $GLOBALS[ "JPEG_Segment_Descriptions" ][ 0xE1 ],
                                                                        "SegData" => "http://ns.adobe.com/xap/1.0/\x00" . $newXMP ) ) );

        // Return the headers with the new segment inserted
        return $jpeg_header_data;
}

/******************************************************************************
* End of Function:     put_XMP_text
******************************************************************************/






/******************************************************************************
*
* Function:     read_XMP_array_from_text
*
* Description:  An alias for read_xml_array_from_text.
*               Parses a string containing XMP data (XML), and returns the resulting
*               tree structure array, which contains all the XMP (XML) information.
*               Note: White space and comments in the XMP data (XML) are ignored
*               Note: All text information contained in the tree structure
*                     is encoded as Unicode UTF-8. Hence text will appear as
*                     normal ASCII except where there is an extended character.
*
* Parameters:   xmptext - a string containing the XMP data (XML) to be parsed
*
* Returns:      output - the tree structure array containing the XMP (XML) information
*               FALSE - if an error occured
*
******************************************************************************/

function read_XMP_array_from_text( $xmptext )
{
        return read_xml_array_from_text( $xmptext );
}

/******************************************************************************
* End of Function:     read_XMP_array_from_text
******************************************************************************/





/******************************************************************************
*
* Function:     write_XMP_array_to_text
*
* Description:  Takes a tree structure array containing XMP (in the same format
*               as returned by read_XMP_array_from_text, and constructs a string
*               containing the equivalent XMP, including the XMP Packet header
*               and trailer. Produces XMP text which has correct indents, encoded
*               using UTF-8.
*               Note: All text information contained in the tree structure
*                     can be either 7-bit ASCII or encoded as Unicode UTF-8,
*                     since UTF-8 passes 7-bit ASCII text unchanged.
*
* Parameters:   xmparray - the tree structure array containing the information to
*                          be converted to XMP text
*
* Returns:      output_XMP_text - the string containing the equivalent XMP text
*
******************************************************************************/

function write_XMP_array_to_text( $xmparray )
{
        // Add the XMP packet header
        // The sequence 0xEFBBBF is the UTF-8 encoded version of the Unicode 搝ero
        // width non-breaking space character