<?php
/**
 * Exifer
 * Extracts EXIF information from digital photos.
 *
 * Copyright © 2003 Jake Olefsky
 * http://www.offsky.com/software/exif/index.php
 * jake@olefsky.com
 *
 * Please see exif.php for the complete information about this software.
 *
 * This program 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.
 *
 * This program 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. http://www.gnu.org/copyleft/gpl.html
 */

/**
 * Looks up the name of the tag
 *
 * @param type $tag
 * @return string
 */
function lookup_GPS_tag($tag) {

	switch($tag) {
		case "0000": $tag = "Version";break;
		case "0001": $tag = "Latitude Reference";break;			//north or south
		case "0002": $tag = "Latitude";break;					//dd mm.mm or dd mm ss
		case "0003": $tag = "Longitude Reference";break;		//east or west
		case "0004": $tag = "Longitude";break;					//dd mm.mm or dd mm ss
		case "0005": $tag = "Altitude Reference";break;			//sea level or below sea level
		case "0006": $tag = "Altitude";break;					//positive rational number
		case "0007": $tag = "Time";break;						//three positive rational numbers
		case "0008": $tag = "Satellite";break;					//text string up to 999 bytes long
		case "0009": $tag = "ReceiveStatus";break;				//in progress or interop
		case "000a": $tag = "MeasurementMode";break;			//2D or 3D
		case "000b": $tag = "MeasurementPrecision";break;		//positive rational number
		case "000c": $tag = "SpeedUnit";break;					//KPH, MPH, knots
		case "000d": $tag = "ReceiverSpeed";break;				//positive rational number
		case "000e": $tag = "MovementDirectionRef";break;		//true or magnetic north
		case "000f": $tag = "MovementDirection";break;			//positive rational number
		case "0010": $tag = "ImageDirectionRef";break;			//true or magnetic north
		case "0011": $tag = "ImageDirection";break;				//positive rational number
		case "0012": $tag = "GeodeticSurveyData";break;			//text string up to 999 bytes long
		case "0013": $tag = "DestLatitudeRef";break;			//north or south
		case "0014": $tag = "DestinationLatitude";break;		//three positive rational numbers
		case "0015": $tag = "DestLongitudeRef";break;			//east or west
		case "0016": $tag = "DestinationLongitude";break;		//three positive rational numbers
		case "0017": $tag = "DestBearingRef";break;				//true or magnetic north
		case "0018": $tag = "DestinationBearing";break;			//positive rational number
		case "0019": $tag = "DestDistanceRef";break;			//km, miles, knots
		case "001a": $tag = "DestinationDistance";break;		//positive rational number
		case "001b": $tag = "ProcessingMethod";break;
		case "001c": $tag = "AreaInformation";break;
		case "001d": $tag = "Datestamp";break;					//text string 10 bytes long
		case "001e": $tag = "DifferentialCorrection";break;		//integer in range 0-65535


		default: $tag = "unknown:".$tag;break;
	}

	return $tag;
}

/**
 * Formats Data for the data type
 *
 * @param type $type
 * @param type $tag
 * @param type $intel
 * @param type $data
 * @return type
 */
function formatGPSData($type, $tag, $intel, $data) {

	if ($type == "ASCII") {
		if ($tag == "0001" || $tag == "0003") { // Latitude Reference, Longitude Reference
			$data = ($data{1} == @$data{2} && @$data{1} == @$data{3}) ? $data{0} : $data;
		}
	} else if ($type == "URATIONAL" || $type == "SRATIONAL") {
		if ($tag == "0002" || $tag == "0004" || $tag == '0007') { //Latitude, Longitude, Time
			$datum = array();
			for ($i = 0; $i < strlen($data); $i = $i + 8) {
				array_push($datum, substr($data, $i, 8));
			}
			$hour = unRational($datum[0], $type, $intel);
			$minutes = unRational($datum[1], $type, $intel);
			$seconds = unRational($datum[2], $type, $intel);
			if ($tag == "0007") { //Time
				$data = $hour . ":" . $minutes . ":" . $seconds;
			} else {
				$data = $hour + $minutes / 60 + $seconds / 3600;
			}
		} else {
			$data = unRational($data, $type, $intel);

			if ($tag == "0006") {
				$data .= 'm';
			}
		}
	} else if ($type == "USHORT" || $type == "SSHORT" || $type == "ULONG" || $type == "SLONG" || $type == "FLOAT" || $type == "DOUBLE") {
		$data = rational($data, $type, $intel);
	} else if ($type == "UNDEFINED") {

	} else if ($type == "UBYTE") {
		$data = bin2hex($data);
		if ($intel == 1)
			$num = intel2Moto($data);

		if ($tag == "0000") { // VersionID
			$data = hexdec(substr($data, 0, 2)) .
							"." . hexdec(substr($data, 2, 2)) .
							"." . hexdec(substr($data, 4, 2)) .
							"." . hexdec(substr($data, 6, 2));
		} else if ($tag == "0005") { // Altitude Reference
			if ($data == "00000000") {
				$data = '+';
			} else if ($data == "01000000") {
				$data = '-';
			}
		}
	} else {
		$data = bin2hex($data);
		if ($intel == 1)
			$data = intel2Moto($data);
	}

	return $data;
}

/**
 * GPS Special data section
 *
 * Useful websites
 *
 * -http://drewnoakes.com/code/exif/sampleOutput.html
 * - http://www.geosnapper.com
 * @param type $block
 * @param type $result
 * @param type $offset
 * @param type $seek
 * @param type $globalOffset
 * @return type
 */
function parseGPS($block,&$result,$offset,$seek, $globalOffset) {

	if($result['Endien']=="Intel") $intel=1;
	else $intel=0;

	$v = fseek($seek,$globalOffset+$offset);  //offsets are from TIFF header which is 12 bytes from the start of the file
	if($v==-1) {
		$result['Errors'] = $result['Errors']++;
	}

	$num = bin2hex(fread( $seek, 2 ));
	if($intel==1) $num = intel2Moto($num);
	$num=hexdec($num);
	$result['GPS']['NumTags'] = $num;

	if ($num == 0) {
		return;
	}

	$block = fread( $seek, $num*12 );
	$place = 0;

	//loop thru all tags  Each field is 12 bytes
	for($i=0;$i<$num;$i++) {
			//2 byte tag
		$tag = bin2hex(substr($block,$place,2));$place+=2;
		if($intel==1) $tag = intel2Moto($tag);
		$tag_name = lookup_GPS_tag($tag);

		//2 byte datatype
		$type = bin2hex(substr($block,$place,2));$place+=2;
		if($intel==1) $type = intel2Moto($type);
		lookup_type($type,$size);

		//4 byte number of elements
		$count = bin2hex(substr($block,$place,4));$place+=4;
		if($intel==1) $count = intel2Moto($count);
		$bytesofdata = validSize($size*hexdec($count));

		//4 byte value or pointer to value if larger than 4 bytes
		$value = substr($block,$place,4);$place+=4;
		if($bytesofdata<=4) {
			$data = substr($value,0,$bytesofdata);
		} else {
			if (strpos('unknown',$tag_name) !== false || $bytesofdata > 1024) {
				$result['Errors'] = $result['Errors']++;
				$data = '';
				$type = 'ASCII';
			} else {
				$value = bin2hex($value);
				if($intel==1) $value = intel2Moto($value);
				$v = fseek($seek,$globalOffset+hexdec($value));  //offsets are from TIFF header which is 12 bytes from the start of the file
				if($v==0) {
					$data = fread($seek, $bytesofdata);
				} else {
					$result['Errors'] = $result['Errors']++;
					$data = '';
					$type = 'ASCII';
				}
			}
		}
		if($result['VerboseOutput']==1) {
			$result['GPS'][$tag_name] = formatGPSData($type,$tag,$intel,$data);
			$result['GPS'][$tag_name."_Verbose"]['RawData'] = bin2hex($data);
			$result['GPS'][$tag_name."_Verbose"]['Type'] = $type;
			$result['GPS'][$tag_name."_Verbose"]['Bytes'] = $bytesofdata;
		} else {
			$result['GPS'][$tag_name] = formatGPSData($type,$tag,$intel,$data);
		}
	}
}