Changing metadata in an photo.

In a previous post I explained a problem I was having extracting metadata from a photo and then adding it back after resizing the photo.

I managed to solve that problem but have since discovered another issue.

When I resize the image the exif data written back to it contains the original size and what I need to store is the new size - but I am now completely lost as to how to go about doing this.

The command to extract the data from the image before resizing is

$exif_data = get_EXIF_JPEG( $filename );

The function 'get_EXIF_JPEG' is not a standard PHP function, but one contained in a separate file (EXIF.php) called as an 'include' in the resizing script.

However I assume that the information is called into an array because a later instruction

put_EXIF_JPEG( $exif_data, $jpeg_header_data );

writes it 'as is' back to the new image.

How can I :

- determine the structure/content of the array

- alter some of the content (ie the size information)

before writing it back to the new image.

Any and all assistance appreciated.

This is the function 'get_EXIF_JPEG' from the included script:

function get_EXIF_JPEG( $filename )
{
        // Change: Added as of version 1.11
        // Check if a wrapper is being used - these are not currently supported (see notes at top of file)
        if ( ( stristr ( $filename, "http://" ) != FALSE ) || ( stristr ( $filename, "ftp://" ) != FALSE ) )
        {
                // A HTTP or FTP wrapper is being used - show a warning and abort
                echo "HTTP and FTP wrappers are currently not supported with EXIF - See EXIF functionality documentation - a local file must be specified<br>";
                echo "To work on an internet file, copy it locally to start with:<br><br>\n";
                echo "\$newfilename = tempnam ( \$dir, \"tmpexif\" );<br>\n";
                echo "copy ( \"http://whatever.com\", \$newfilename );<br><br>\n";
                return FALSE;
        }

        // get the JPEG headers
        $jpeg_header_data = get_jpeg_header_data( $filename );


        // Flag that an EXIF segment has not been found yet
        $EXIF_Location = -1;

        //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 EXIF label,
                        if ( ( strncmp ( $jpeg_header_data[$i]['SegData'], "Exif\x00\x00", 6) == 0 ) ||
                             ( strncmp ( $jpeg_header_data[$i]['SegData'], "Exif\x00\xFF", 6) == 0 ) )          // For some reason, some files have a faulty EXIF name which has a 0xFF in it
                        {
                                // Save the location of the EXIF segment
                                $EXIF_Location = $i;
                        }
                }

        }

        // Check if an EXIF segment was found
        if ( $EXIF_Location == -1 )
        {
                // Couldn't find any EXIF block to decode
                return FALSE;
        }

        $filehnd = @fopen($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;
        }

        fseek( $filehnd, $jpeg_header_data[$EXIF_Location]['SegDataStart'] + 6  );

        // Decode the Exif segment into an array and return it
        $exif_data = process_TIFF_Header( $filehnd, "TIFF" );



        // Close File
        fclose($filehnd);
        return $exif_data;
}