jpeg.php

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<?php

/******************************************************************************
*
* Filename:     JPEG.php
*
* Description:  Provides functions for reading and writing information to/from
*               JPEG format files
*
* Author:       Evan Hunter
*
* Date:         23/7/2004
*
* Project:      PHP JPEG Metadata Toolkit
*
* Revision:     1.10
*
* Changes:      1.00 -> 1.10 : changed put_jpeg_header_data to check if the data
*                              being written exists
*
* 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]
*
******************************************************************************/




/******************************************************************************
*
* Function:     get_jpeg_header_data
*
* Description:  Reads all the JPEG header segments from an JPEG image file into an
*               array
*
* Parameters:   filename - the filename of the file to JPEG file to read
*
* Returns:      headerdata - Array of JPEG header segments
*               FALSE - if headers could not be read
*
******************************************************************************/

function get_jpeg_header_data( $filename )
{

        // prevent refresh from aborting file operations and hosing file
        ignore_user_abort(true);


        // Attempt to open the jpeg file - the at symbol supresses the error message about
        // not being able to open files. The file_exists would have been used, but it
        // does not work with files fetched over http or ftp.
        $filehnd = @fopen($filename, 'rb');

        // Check if the file opened successfully
        if ( ! $filehnd  )
        {
                // Could't open the file - exit
                echo "<p>Could not open file $filename</p>\n";
                return FALSE;
        }


        // Read the first two characters
        $data = network_safe_fread( $filehnd, 2 );

        // Check that the first two characters are 0xFF 0xDA  (SOI - Start of image)
        if ( $data != "\xFF\xD8" )
        {
                // No SOI (FF D8) at start of file - This probably isn't a JPEG file - close file and return;
                //echo "<p>This probably is not a JPEG file</p>\n";
                fclose($filehnd);
                return FALSE;
        }


        // Read the third character
        $data = network_safe_fread( $filehnd, 2 );

        // Check that the third character is 0xFF (Start of first segment header)
        if ( $data{0} != "\xFF" )
        {
                // NO FF found - close file and return - JPEG is probably corrupted
                fclose($filehnd);
                return FALSE;
        }

        // Flag that we havent yet hit the compressed image data
        $hit_compressed_image_data = FALSE;


        // Cycle through the file until, one of: 1) an EOI (End of image) marker is hit,
        //                                       2) we have hit the compressed image data (no more headers are allowed after data)
        //                                       3) or end of file is hit

        while ( ( $data{1} != "\xD9" ) && (! $hit_compressed_image_data) && ( ! feof( $filehnd ) ))
        {
                // Found a segment to look at.
                // Check that the segment marker is not a Restart marker - restart markers don't have size or data after them
                if (  ( ord($data{1}) < 0xD0 ) || ( ord($data{1}) > 0xD7 ) )
                {
                        // Segment isn't a Restart marker
                        // Read the next two bytes (size)
                        $sizestr = network_safe_fread( $filehnd, 2 );

                        // convert the size bytes to an integer
                        $decodedsize = unpack ("nsize", $sizestr);

                        // Save the start position of the data
                        $segdatastart = ftell( $filehnd );

                        // Read the segment data with length indicated by the previously read size
                        $segdata = network_safe_fread( $filehnd, $decodedsize['size'] - 2 );


                        // Store the segment information in the output array
                        $headerdata[] = array(  "SegType" => ord($data{1}),
                                                "SegName" => $GLOBALS[ "JPEG_Segment_Names" ][ ord($data{1}) ],
                                                "SegDesc" => $GLOBALS[ "JPEG_Segment_Descriptions" ][ ord($data{1}) ],
                                                "SegDataStart" => $segdatastart,
                                                "SegData" => $segdata );
                }

                // If this is a SOS (Start Of Scan) segment, then there is no more header data - the compressed image data follows
                if ( $data{1} == "\xDA" )
                {
                        // Flag that we have hit the compressed image data - exit loop as no more headers available.
                        $hit_compressed_image_data = TRUE;
                }
                else
                {
                        // Not an SOS - Read the next two bytes - should be the segment marker for the next segment
                        $data = network_safe_fread( $filehnd, 2 );

                        // Check that the first byte of the two is 0xFF as it should be for a marker
                        if ( $data{0} != "\xFF" )
                        {
                                // NO FF found - close file and return - JPEG is probably corrupted
                                fclose($filehnd);
                                return FALSE;
                        }
                }
        }

        // Close File
        fclose($filehnd);
        // Alow the user to abort from now on
        ignore_user_abort(false);

        // Return the header data retrieved
        return $headerdata;
}


/******************************************************************************
* End of Function:     get_jpeg_header_data
******************************************************************************/




/******************************************************************************
*
* Function:     put_jpeg_header_data
*
* Description:  Writes JPEG header data into a JPEG file. Takes an array in the
*               same format as from get_jpeg_header_data, and combines it with
*               the image data of an existing JPEG file, to create a new JPEG file
*               WARNING: As this function will replace all JPEG headers,
*                        including SOF etc, it is best to read the jpeg headers
*                        from a file, alter them, then put them back on the same
*                        file. If a SOF segment wer to be transfered from one
*                        file to another, the image could become unreadable unless
*                        the images were idenical size and configuration
*
*
* Parameters:   old_filename - the JPEG file from which the image data will be retrieved
*               new_filename - the name of the new JPEG to create (can be same as old_filename)
*               jpeg_header_data - a JPEG header data array in the same format
*                                  as from get_jpeg_header_data
*
* Returns:      TRUE - on Success
*               FALSE - on Failure
*
******************************************************************************/

function put_jpeg_header_data( $old_filename, $new_filename, $jpeg_header_data )
{

        // Change: added check to ensure data exists, as of revision 1.10
        // Check if the data to be written exists
        if ( $jpeg_header_data == FALSE )
        {
                // Data to be written not valid - abort
                return FALSE;
        }

        // extract the compressed image data from the old file
        $compressed_image_data = get_jpeg_image_data( $old_filename );

        // Check if the extraction worked
        if ( ( $compressed_image_data === FALSE ) || ( $compressed_image_data === NULL ) )
        {
                // Couldn't get image data from old file
                return FALSE;
        }


        // Cycle through new headers
        foreach ($jpeg_header_data as $segno => $segment)
        {
                // Check that this header is smaller than the maximum size
                if ( strlen($segment['SegData']) > 0xfffd )
                {
                        // Could't open the file - exit
                        echo "<p>A Header is too large to fit in JPEG segment</p>\n";
                        return FALSE;
                }
        }

        ignore_user_abort(true);    ## prevent refresh from aborting file operations and hosing file


        // Attempt to open the new jpeg file
        $newfilehnd = @fopen($new_filename, 'wb');
        // Check if the file opened successfully
        if ( ! $newfilehnd  )
        {
                // Could't open the file - exit
                echo "<p>Could not open file $new_filename</p>\n";
                return FALSE;
        }

        // Write SOI
        fwrite( $newfilehnd, "\xFF\xD8" );

        // Cycle through new headers, writing them to the new file
        foreach ($jpeg_header_data as $segno => $segment)
        {

                // Write segment marker
                fwrite( $newfilehnd, sprintf( "\xFF%c", $segment['SegType'] ) );

                // Write segment size
                fwrite( $newfilehnd, pack( "n", strlen($segment['SegData']) + 2 ) );

                // Write segment data
                fwrite( $newfilehnd, $segment['SegData'] );
        }

        // Write the compressed image data
        fwrite( $newfilehnd, $compressed_image_data );

        // Write EOI
        fwrite( $newfilehnd, "\xFF\xD9" );

        // Close File
        fclose($newfilehnd);

        // Alow the user to abort from now on
        ignore_user_abort(false);


        return TRUE;

}

/******************************************************************************
* End of Function:     put_jpeg_header_data
******************************************************************************/



/******************************************************************************
*
* Function:     get_jpeg_Comment
*
* Description:  Retreives the contents of the JPEG Comment (COM = 0xFFFE) segment if one
*               exists
*
* Parameters:   jpeg_header_data - the JPEG header data, as retrieved
*                                  from the get_jpeg_header_data function
*
* Returns:      string - Contents of the Comment segement
*               FALSE - if the comment segment couldnt be found
*
******************************************************************************/

function get_jpeg_Comment( $jpeg_header_data )
{
        //Cycle through the header segments until COM is found or we run out of segments
        $i = 0;
        while ( ( $i < count( $jpeg_header_data) )  && ( $jpeg_header_data[$i]['SegName'] != "COM" ) )
        {
                $i++;
        }

        // Check if a COM segment has been found
        if (  $i < count( $jpeg_header_data) )
        {
                // A COM segment was found, return it's contents
                return $jpeg_header_data[$i]['SegData'];