path: root/resources/mediawiki.libs/mediawiki.libs.jpegmeta.js

/* This is JsJpegMeta 1.0, ported to MediaWiki ResourceLoader by Bryan Tong Minh */
/* The following lines where changed with respect to the original: 54, 625-627 */

(function( $ ) {

	/* JsJpegMeta starts here */
	
	/*
	Copyright (c) 2009 Ben Leslie
	
	Permission is hereby granted, free of charge, to any person obtaining a copy
	of this software and associated documentation files (the "Software"), to deal
	in the Software without restriction, including without limitation the rights
	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	copies of the Software, and to permit persons to whom the Software is
	furnished to do so, subject to the following conditions:
	
	The above copyright notice and this permission notice shall be included in
	all copies or substantial portions of the Software.
	
	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	THE SOFTWARE.
	*/
	
	/*
	 This JavaScript library is used to parse meta-data from files 
	 with mime-type image/jpeg.
	
	 Include it with something like:
	
	   <script type="text/javascript" src="jpegmeta.js"></script>
	
	 This adds a single 'module' object called 'JpegMeta' to the global
	 namespace.
	
	 Public Functions
	 ----------------
	 JpegMeta.parseNum - parse unsigned integers from binary data
	 JpegMeta.parseSnum - parse signed integers from binary data
	
	 Public Classes
	 --------------
	 JpegMeta.Rational - A rational number class
	 JpegMeta.JfifSegment
	 JpegMeta.ExifSegment
	 JpegMeta.JpegFile - Primary class for Javascript parsing
	*/

	var JpegMeta = {};
	this.JpegMeta = JpegMeta; // I have no clue why I need this magic... -- Bryan
	
	/* 
	   parse an unsigned number of size bytes at offset in some binary string data.
	   If endian
	   is "<" parse the data as little endian, if endian
	   is ">" parse as big-endian.
	*/
	JpegMeta.parseNum = function parseNum(endian, data, offset, size) {
	    var i;
	    var ret;
	    var big_endian = (endian === ">");
	    if (offset === undefined) offset = 0;
	    if (size === undefined) size = data.length - offset;
	    for (big_endian ? i = offset : i = offset + size - 1; 
		 big_endian ? i < offset + size : i >= offset; 
		 big_endian ? i++ : i--) {
		ret <<= 8;
		ret += data.charCodeAt(i);
	    }
	    return ret;
	};
	
	/* 
	   parse an signed number of size bytes at offset in some binary string data.
	   If endian
	   is "<" parse the data as little endian, if endian
	   is ">" parse as big-endian.
	*/
	JpegMeta.parseSnum = function parseSnum(endian, data, offset, size) {
	    var i;
	    var ret;
	    var neg;
	    var big_endian = (endian === ">");
	    if (offset === undefined) offset = 0;
	    if (size === undefined) size = data.length - offset;
	    for (big_endian ? i = offset : i = offset + size - 1; 
		 big_endian ? i < offset + size : i >= offset; 
		 big_endian ? i++ : i--) {
		if (neg === undefined) {
		    /* Negative if top bit is set */
		    neg = (data.charCodeAt(i) & 0x80) === 0x80;
		}
		ret <<= 8;
		/* If it is negative we invert the bits */
		ret += neg ? ~data.charCodeAt(i) & 0xff: data.charCodeAt(i);
	    }
	    if (neg) {
		/* If it is negative we do two's complement */
		ret += 1;
		ret *= -1;
	    }
	    return ret;
	};
	
	/* Rational number class */
	JpegMeta.Rational = function Rational(num, den)
	{
	    this.num = num;
	    this.den = den || 1;
	    return this;
	};
	
	/* Rational number methods */
	JpegMeta.Rational.prototype.toString = function toString() {
	    if (this.num === 0) {
		return "" + this.num;
	    }
	    if (this.den === 1) {
		return "" + this.num;
	    }
	    if (this.num === 1) {
		return this.num + " / " + this.den;
	    }
	    return this.num / this.den; // + "/" + this.den;
	};
	
	JpegMeta.Rational.prototype.asFloat = function asFloat() {
	    return this.num / this.den;
	};
	
	/* MetaGroup class */
	JpegMeta.MetaGroup = function MetaGroup(fieldName, description) {
	    this.fieldName = fieldName;
	    this.description = description;
	    this.metaProps = {};
	    return this;
	};
	
	JpegMeta.MetaGroup.prototype._addProperty = function _addProperty(fieldName, description, value) {
	    var property = new JpegMeta.MetaProp(fieldName, description, value);
	    this[property.fieldName] = property;
	    this.metaProps[property.fieldName] = property;
	};
	
	JpegMeta.MetaGroup.prototype.toString = function toString() {
	    return "[MetaGroup " + this.description + "]";
	};

	/* MetaProp class */
	JpegMeta.MetaProp = function MetaProp(fieldName, description, value) {
	    this.fieldName = fieldName;
	    this.description = description;
	    this.value = value;
	    return this;
	};
	
	JpegMeta.MetaProp.prototype.toString = function toString() {
	    return "" + this.value;
	};

	/* JpegFile class */
	JpegMeta.JpegFile = function JpegFile(binary_data, filename) {
	    /* Change this to EOI if we want to parse. */
	    var break_segment = this._SOS;
	    
	    this.metaGroups = {};
	    this._binary_data = binary_data;
	    this.filename = filename;
	    
	    /* Go through and parse. */
	    var pos = 0;
	    var pos_start_of_segment = 0;
	    var delim;
	    var mark;
	    var _mark;
	    var segsize;
	    var headersize;
	    var mark_code;
	    var mark_fn;
	
	    /* Check to see if this looks like a JPEG file */
	    if (this._binary_data.slice(0, 2) !== this._SOI_MARKER) {
		throw new Error("Doesn't look like a JPEG file. First two bytes are " + 
				this._binary_data.charCodeAt(0) + "," + 
				this._binary_data.charCodeAt(1) + ".");
	    }
	    
	    pos += 2;
	    
	    while (pos < this._binary_data.length) {
		delim = this._binary_data.charCodeAt(pos++);
		mark = this._binary_data.charCodeAt(pos++);
		
		pos_start_of_segment = pos;
		
		if (delim != this._DELIM) {
		    break;
		}
		
		if (mark === break_segment) {
		    break;
		}
		
		headersize = JpegMeta.parseNum(">", this._binary_data, pos, 2);
		
		/* Find the end */
		pos += headersize;
		while (pos < this._binary_data.length) {
		    delim = this._binary_data.charCodeAt(pos++);
		    if (delim == this._DELIM) {
			_mark = this._binary_data.charCodeAt(pos++);
			if (_mark != 0x0) {
			    pos -= 2;
			    break;
			}
		    }
		}
		
		segsize = pos - pos_start_of_segment;
		
		if (this._markers[mark]) {
		    mark_code = this._markers[mark][0];
		    mark_fn = this._markers[mark][1];
		} else {
		    mark_code = "UNKN";
		    mark_fn = undefined;
		}
		
		if (mark_fn) {
		    this[mark_fn](mark, pos_start_of_segment + 2);
		}
		
	    }
	    
	    if (this.general === undefined) {
		throw Error("Invalid JPEG file.");
	    }
	    
	    return this;
	};
	
	this.JpegMeta.JpegFile.prototype.toString = function () {
	    return "[JpegFile " + this.filename + " " + 
		this.general.type + " " + 
		this.general.pixelWidth + "x" + 
		this.general.pixelHeight +
		" Depth: " + this.general.depth + "]";
	};
	
	/* Some useful constants */
	this.JpegMeta.JpegFile.prototype._SOI_MARKER = '\xff\xd8';
	this.JpegMeta.JpegFile.prototype._DELIM = 0xff;
	this.JpegMeta.JpegFile.prototype._EOI = 0xd9;
	this.JpegMeta.JpegFile.prototype._SOS = 0xda;
	
	this.JpegMeta.JpegFile.prototype._sofHandler = function _sofHandler (mark, pos) {
	    if (this.general !== undefined) {
		throw Error("Unexpected multiple-frame image");
	    }
	
	    this._addMetaGroup("general", "General");
	    this.general._addProperty("depth", "Depth", JpegMeta.parseNum(">", this._binary_data, pos, 1));
	    this.general._addProperty("pixelHeight", "Pixel Height", JpegMeta.parseNum(">", this._binary_data, pos + 1, 2));
	    this.general._addProperty("pixelWidth", "Pixel Width",JpegMeta.parseNum(">", this._binary_data, pos + 3, 2));
	    this.general._addProperty("type", "Type", this._markers[mark][2]);
	};
	
	/* JFIF idents */
	this.JpegMeta.JpegFile.prototype._JFIF_IDENT = "JFIF\x00";
	this.JpegMeta.JpegFile.prototype._JFXX_IDENT = "JFXX\x00";
	
	/* Exif idents */
	this.JpegMeta.JpegFile.prototype._EXIF_IDENT = "Exif\x00";
	
	/* TIFF types */
	this.JpegMeta.JpegFile.prototype._types = {
	    /* The format is identifier : ["type name", type_size_in_bytes ] */
	    1 : ["BYTE", 1],
	    2 : ["ASCII", 1],
	    3 : ["SHORT", 2],
	    4 : ["LONG", 4],
	    5 : ["RATIONAL", 8],
	    6 : ["SBYTE", 1],
	    7 : ["UNDEFINED", 1],
	    8 : ["SSHORT", 2],
	    9 : ["SLONG", 4],
	    10 : ["SRATIONAL", 8],
	    11 : ["FLOAT", 4],
	    12 : ["DOUBLE", 8]
	};
	
	this.JpegMeta.JpegFile.prototype._tifftags = {
	    /* A. Tags relating to image data structure */
	    256 : ["Image width", "ImageWidth"],
	    257 : ["Image height", "ImageLength"],
	    258 : ["Number of bits per component", "BitsPerSample"],
	    259 : ["Compression scheme", "Compression", 
		   {1 : "uncompressed", 6 : "JPEG compression" }],
	    262 : ["Pixel composition", "PhotmetricInerpretation",
		   {2 : "RGB", 6 : "YCbCr"}],
	    274 : ["Orientation of image", "Orientation",
		   /* FIXME: Check the mirror-image / reverse encoding and rotation */
		   {1 : "Normal", 2 : "Reverse?", 
		    3 : "Upside-down", 4 : "Upside-down Reverse",
		    5 : "90 degree CW", 6 : "90 degree CW reverse",
		    7 : "90 degree CCW", 8 : "90 degree CCW reverse"}],
	    277 : ["Number of components", "SamplesPerPixel"],
	    284 : ["Image data arrangement", "PlanarConfiguration",
		   {1 : "chunky format", 2 : "planar format"}],
	    530 : ["Subsampling ratio of Y to C", "YCbCrSubSampling"],
	    531 : ["Y and C positioning", "YCbCrPositioning",
		   {1 : "centered", 2 : "co-sited"}],
	    282 : ["X Resolution", "XResolution"],
	    283 : ["Y Resolution", "YResolution"],
	    296 : ["Resolution Unit", "ResolutionUnit",
		   {2 : "inches", 3 : "centimeters"}],
	    /* B. Tags realting to recording offset */
	    273 : ["Image data location", "StripOffsets"],
	    278 : ["Number of rows per strip", "RowsPerStrip"],
	    279 : ["Bytes per compressed strip", "StripByteCounts"],
	    513 : ["Offset to JPEG SOI", "JPEGInterchangeFormat"],
	    514 : ["Bytes of JPEG Data", "JPEGInterchangeFormatLength"],
	    /* C. Tags relating to image data characteristics */
	    301 : ["Transfer function", "TransferFunction"],
	    318 : ["White point chromaticity", "WhitePoint"],
	    319 : ["Chromaticities of primaries", "PrimaryChromaticities"],
	    529 : ["Color space transformation matrix coefficients", "YCbCrCoefficients"],
	    532 : ["Pair of black and white reference values", "ReferenceBlackWhite"],
	    /* D. Other tags */
	    306 : ["Date and time", "DateTime"],
	    270 : ["Image title", "ImageDescription"],
	    271 : ["Make", "Make"],
	    272 : ["Model", "Model"],
	    305 : ["Software", "Software"],
	    315 : ["Person who created the image", "Artist"],
	    316 : ["Host Computer", "HostComputer"],
	    33432 : ["Copyright holder", "Copyright"],
	    
	    34665 : ["Exif tag", "ExifIfdPointer"],
	    34853 : ["GPS tag", "GPSInfoIfdPointer"]
	};
	
	this.JpegMeta.JpegFile.prototype._exiftags = {
	    /* Tag Support Levels (2) - 0th IFX Exif Private Tags */
	    /* A. Tags Relating to Version */
	    36864 : ["Exif Version", "ExifVersion"],
	    40960 : ["FlashPix Version", "FlashpixVersion"],
	    
	    /* B. Tag Relating to Image Data Characteristics */
	    40961 : ["Color Space", "ColorSpace"],
	    
	    /* C. Tags Relating to Image Configuration */
	    37121 : ["Meaning of each component", "ComponentsConfiguration"],
	    37122 : ["Compressed Bits Per Pixel", "CompressedBitsPerPixel"],
	    40962 : ["Pixel X Dimension", "PixelXDimension"],
	    40963 : ["Pixel Y Dimension", "PixelYDimension"],
	    
	    /* D. Tags Relating to User Information */
	    37500 : ["Manufacturer notes", "MakerNote"],
	    37510 : ["User comments", "UserComment"],
	    
	    /* E. Tag Relating to Related File Information */
	    40964 : ["Related audio file", "RelatedSoundFile"],
	    
	    /* F. Tags Relating to Date and Time */
	    36867 : ["Date Time Original", "DateTimeOriginal"],
	    36868 : ["Date Time Digitized", "DateTimeDigitized"],
	    37520 : ["DateTime subseconds", "SubSecTime"],
	    37521 : ["DateTimeOriginal subseconds", "SubSecTimeOriginal"],
	    37522 : ["DateTimeDigitized subseconds", "SubSecTimeDigitized"],
	    
	    /* G. Tags Relating to Picture-Taking Conditions */
	    33434 : ["Exposure time", "ExposureTime"],
	    33437 : ["FNumber", "FNumber"],
	    34850 : ["Exposure program", "ExposureProgram"],
	    34852 : ["Spectral sensitivity", "SpectralSensitivity"],
	    34855 : ["ISO Speed Ratings", "ISOSpeedRatings"],
	    34856 : ["Optoelectric coefficient", "OECF"],
	    37377 : ["Shutter Speed",  "ShutterSpeedValue"],
	    37378 : ["Aperture Value", "ApertureValue"],
	    37379 : ["Brightness", "BrightnessValue"],
	    37380 : ["Exposure Bias Value", "ExposureBiasValue"],
	    37381 : ["Max Aperture Value", "MaxApertureValue"],
	    37382 : ["Subject Distance", "SubjectDistance"],
	    37383 : ["Metering Mode", "MeteringMode"],
	    37384 : ["Light Source", "LightSource"],
	    37385 : ["Flash", "Flash"],
	    37386 : ["Focal Length", "FocalLength"],
	    37396 : ["Subject Area", "SubjectArea"],
	    41483 : ["Flash Energy", "FlashEnergy"],
	    41484 : ["Spatial Frequency Response", "SpatialFrequencyResponse"],
	    41486 : ["Focal Plane X Resolution", "FocalPlaneXResolution"],
	    41487 : ["Focal Plane Y Resolution", "FocalPlaneYResolution"],
	    41488 : ["Focal Plane Resolution Unit", "FocalPlaneResolutionUnit"],
	    41492 : ["Subject Location", "SubjectLocation"],
	    41493 : ["Exposure Index", "ExposureIndex"],
	    41495 : ["Sensing Method", "SensingMethod"],
	    41728 : ["File Source", "FileSource"],
	    41729 : ["Scene Type", "SceneType"],
	    41730 : ["CFA Pattern", "CFAPattern"],
	    41985 : ["Custom Rendered", "CustomRendered"],
	    41986 : ["Exposure Mode", "Exposure Mode"],
	    41987 : ["White Balance", "WhiteBalance"],
	    41988 : ["Digital Zoom Ratio", "DigitalZoomRatio"],
	    41990 : ["Scene Capture Type", "SceneCaptureType"],
	    41991 : ["Gain Control", "GainControl"],
	    41992 : ["Contrast", "Contrast"],
	    41993 : ["Saturation", "Saturation"],
	    41994 : ["Sharpness", "Sharpness"],
	    41995 : ["Device settings description", "DeviceSettingDescription"],
	    41996 : ["Subject distance range", "SubjectDistanceRange"],
	    
	    /* H. Other Tags */
	    42016 : ["Unique image ID", "ImageUniqueID"],
	    
	    40965 : ["Interoperability tag", "InteroperabilityIFDPointer"]
	};
	
	this.JpegMeta.JpegFile.prototype._gpstags = {
	    /* A. Tags Relating to GPS */
	    0 : ["GPS tag version", "GPSVersionID"],
	    1 : ["North or South Latitude", "GPSLatitudeRef"],
	    2 : ["Latitude", "GPSLatitude"],
	    3 : ["East or West Longitude", "GPSLongitudeRef"],
	    4 : ["Longitude", "GPSLongitude"],
	    5 : ["Altitude reference", "GPSAltitudeRef"],
	    6 : ["Altitude", "GPSAltitude"],
	    7 : ["GPS time (atomic clock)", "GPSTimeStamp"],
	    8 : ["GPS satellites usedd for measurement", "GPSSatellites"],
	    9 : ["GPS receiver status", "GPSStatus"],
	    10 : ["GPS mesaurement mode", "GPSMeasureMode"],
	    11 : ["Measurement precision", "GPSDOP"],
	    12 : ["Speed unit", "GPSSpeedRef"],
	    13 : ["Speed of GPS receiver", "GPSSpeed"],
	    14 : ["Reference for direction of movement", "GPSTrackRef"],
	    15 : ["Direction of movement", "GPSTrack"],
	    16 : ["Reference for direction of image", "GPSImgDirectionRef"],
	    17 : ["Direction of image", "GPSImgDirection"],
	    18 : ["Geodetic survey data used", "GPSMapDatum"],
	    19 : ["Reference for latitude of destination", "GPSDestLatitudeRef"],
	    20 : ["Latitude of destination", "GPSDestLatitude"],
	    21 : ["Reference for longitude of destination", "GPSDestLongitudeRef"],
	    22 : ["Longitude of destination", "GPSDestLongitude"],
	    23 : ["Reference for bearing of destination", "GPSDestBearingRef"],
	    24 : ["Bearing of destination", "GPSDestBearing"],
	    25 : ["Reference for distance to destination", "GPSDestDistanceRef"],
	    26 : ["Distance to destination", "GPSDestDistance"],
	    27 : ["Name of GPS processing method", "GPSProcessingMethod"],
	    28 : ["Name of GPS area", "GPSAreaInformation"],
	    29 : ["GPS Date", "GPSDateStamp"],
	    30 : ["GPS differential correction", "GPSDifferential"]
	};

	this.JpegMeta.JpegFile.prototype._markers = {
	    /* Start Of Frame markers, non-differential, Huffman coding */
	    0xc0: ["SOF0", "_sofHandler", "Baseline DCT"],
	    0xc1: ["SOF1", "_sofHandler", "Extended sequential DCT"],
	    0xc2: ["SOF2", "_sofHandler", "Progressive DCT"],
	    0xc3: ["SOF3", "_sofHandler", "Lossless (sequential)"],
	    
	    /* Start Of Frame markers, differential, Huffman coding */
	    0xc5: ["SOF5", "_sofHandler", "Differential sequential DCT"],
	    0xc6: ["SOF6", "_sofHandler", "Differential progressive DCT"],
	    0xc7: ["SOF7", "_sofHandler", "Differential lossless (sequential)"],
	    
	    /* Start Of Frame markers, non-differential, arithmetic coding */
	    0xc8: ["JPG", null, "Reserved for JPEG extensions"],
	    0xc9: ["SOF9", "_sofHandler", "Extended sequential DCT"],
	    0xca: ["SOF10", "_sofHandler", "Progressive DCT"],
	    0xcb: ["SOF11", "_sofHandler", "Lossless (sequential)"],
	    
	    /* Start Of Frame markers, differential, arithmetic coding */
	    0xcd: ["SOF13", "_sofHandler", "Differential sequential DCT"],
	    0xce: ["SOF14", "_sofHandler", "Differential progressive DCT"],
	    0xcf: ["SOF15", "_sofHandler", "Differential lossless (sequential)"],
	    
	    /* Huffman table specification */
	    0xc4: ["DHT", null, "Define Huffman table(s)"],
	    0xcc: ["DAC", null, "Define arithmetic coding conditioning(s)"],
	    
	    /* Restart interval termination" */
	    0xd0: ["RST0", null, "Restart with modulo 8 count “0”"],
	    0xd1: ["RST1", null, "Restart with modulo 8 count “1”"],
	    0xd2: ["RST2", null, "Restart with modulo 8 count “2”"],
	    0xd3: ["RST3", null, "Restart with modulo 8 count “3”"],
	    0xd4: ["RST4", null, "Restart with modulo 8 count “4”"],
	    0xd5: ["RST5", null, "Restart with modulo 8 count “5”"],
	    0xd6: ["RST6", null, "Restart with modulo 8 count “6”"],
	    0xd7: ["RST7", null, "Restart with modulo 8 count “7”"],
	    
	    /* Other markers */
	    0xd8: ["SOI", null, "Start of image"],
	    0xd9: ["EOI", null, "End of image"],
	    0xda: ["SOS", null, "Start of scan"],
	    0xdb: ["DQT", null, "Define quantization table(s)"],
	    0xdc: ["DNL", null, "Define number of lines"],
	    0xdd: ["DRI", null, "Define restart interval"],
	    0xde: ["DHP", null, "Define hierarchical progression"],
	    0xdf: ["EXP", null, "Expand reference component(s)"],
	    0xe0: ["APP0", "_app0Handler", "Reserved for application segments"],
	    0xe1: ["APP1", "_app1Handler"],
	    0xe2: ["APP2", null],
	    0xe3: ["APP3", null],
	    0xe4: ["APP4", null],
	    0xe5: ["APP5", null],
	    0xe6: ["APP6", null],
	    0xe7: ["APP7", null],
	    0xe8: ["APP8", null],
	    0xe9: ["APP9", null],
	    0xea: ["APP10", null],
	    0xeb: ["APP11", null],
	    0xec: ["APP12", null],
	    0xed: ["APP13", null],
	    0xee: ["APP14", null],
	    0xef: ["APP15", null],
	    0xf0: ["JPG0", null], /* Reserved for JPEG extensions */
	    0xf1: ["JPG1", null],
	    0xf2: ["JPG2", null],
	    0xf3: ["JPG3", null],
	    0xf4: ["JPG4", null],
	    0xf5: ["JPG5", null],
	    0xf6: ["JPG6", null],
	    0xf7: ["JPG7", null],
	    0xf8: ["JPG8", null],
	    0xf9: ["JPG9", null],
	    0xfa: ["JPG10", null],
	    0xfb: ["JPG11", null],
	    0xfc: ["JPG12", null],
	    0xfd: ["JPG13", null],
	    0xfe: ["COM", null], /* Comment */
	    
	    /* Reserved markers */
	    0x01: ["JPG13", null] /* For temporary private use in arithmetic coding */
	    /* 02 -> bf are reserverd */
	};

	/* Private methods */
	this.JpegMeta.JpegFile.prototype._addMetaGroup = function _addMetaGroup(name, description) {
	    var group = new JpegMeta.MetaGroup(name, description);
	    this[group.fieldName] = group;
	    this.metaGroups[group.fieldName] = group;
	    return group;
	};

	this.JpegMeta.JpegFile.prototype._parseIfd = function _parseIfd(endian, _binary_data, base, ifd_offset, tags, name, description) {
	    var num_fields = JpegMeta.parseNum(endian, _binary_data, base + ifd_offset, 2);
	    /* Per tag variables */
	    var i, j;
	    var tag_base;
	    var tag_field;
	    var type, type_field, type_size;
	    var num_values;
	    var value_offset;
	    var value;
	    var _val;
	    var num;
	    var den;
	    
	    var group;
	    
	    group = this._addMetaGroup(name, description);
	
	    for (var i = 0; i < num_fields; i++) {
		/* parse the field */
		tag_base = base + ifd_offset + 2 + (i * 12);
		tag_field = JpegMeta.parseNum(endian, _binary_data, tag_base, 2);
		type_field = JpegMeta.parseNum(endian, _binary_data, tag_base + 2, 2);
		num_values = JpegMeta.parseNum(endian, _binary_data, tag_base + 4, 4);
		value_offset = JpegMeta.parseNum(endian, _binary_data, tag_base + 8, 4);
		if (this._types[type_field] === undefined) {
		    continue;
		}
		type = this._types[type_field][0];
		type_size = this._types[type_field][1];
		
		if (type_size * num_values <= 4) {
		    /* Data is in-line */
		    value_offset = tag_base + 8;
		} else {
		    value_offset = base + value_offset;
		}
		
		/* Read the value */
		if (type == "UNDEFINED") {
		    value = _binary_data.slice(value_offset, value_offset + num_values);
		} else if (type == "ASCII") {
		    value = _binary_data.slice(value_offset, value_offset + num_values);
		    value = value.split('\x00')[0];
		    /* strip trail nul */
		} else {
		    value = new Array();
		    for (j = 0; j < num_values; j++, value_offset += type_size) {
			if (type == "BYTE" || type == "SHORT" || type == "LONG") {
			    value.push(JpegMeta.parseNum(endian, _binary_data, value_offset, type_size));
			}
			if (type == "SBYTE" || type == "SSHORT" || type == "SLONG") {
			    value.push(JpegMeta.parseSnum(endian, _binary_data, value_offset, type_size));
			}
			if (type == "RATIONAL") {
			    num = JpegMeta.parseNum(endian, _binary_data, value_offset, 4);
			    den = JpegMeta.parseNum(endian, _binary_data, value_offset + 4, 4);
			    value.push(new JpegMeta.Rational(num, den));
			}
			if (type == "SRATIONAL") {
			    num = JpegMeta.parseSnum(endian, _binary_data, value_offset, 4);
			    den = JpegMeta.parseSnum(endian, _binary_data, value_offset + 4, 4);
			    value.push(new JpegMeta.Rational(num, den));
			}
			value.push();
		    }
		    if (num_values === 1) {
			value = value[0];
		    }
		}
		if (tags[tag_field] !== undefined) {
			group._addProperty(tags[tag_field][1], tags[tag_field][0], value);
		}
	    }
	};

	this.JpegMeta.JpegFile.prototype._jfifHandler = function _jfifHandler(mark, pos) {
	    if (this.jfif !== undefined) {
		throw Error("Multiple JFIF segments found");
	    }
	    this._addMetaGroup("jfif", "JFIF");
	    this.jfif._addProperty("version_major", "Version Major", this._binary_data.charCodeAt(pos + 5));
	    this.jfif._addProperty("version_minor", "Version Minor", this._binary_data.charCodeAt(pos + 6));
	    this.jfif._addProperty("version", "JFIF Version", this.jfif.version_major.value + "." + this.jfif.version_minor.value);
	    this.jfif._addProperty("units", "Density Unit", this._binary_data.charCodeAt(pos + 7));
	    this.jfif._addProperty("Xdensity", "X density", JpegMeta.parseNum(">", this._binary_data, pos + 8, 2));
	    this.jfif._addProperty("Ydensity", "Y Density", JpegMeta.parseNum(">", this._binary_data, pos + 10, 2));
	    this.jfif._addProperty("Xthumbnail", "X Thumbnail", JpegMeta.parseNum(">", this._binary_data, pos + 12, 1));
	    this.jfif._addProperty("Ythumbnail", "Y Thumbnail", JpegMeta.parseNum(">", this._binary_data, pos + 13, 1));
	};

	/* Handle app0 segments */
	this.JpegMeta.JpegFile.prototype._app0Handler = function app0Handler(mark, pos) {
	    var ident = this._binary_data.slice(pos, pos + 5);
	    if (ident == this._JFIF_IDENT) {
		this._jfifHandler(mark, pos);
	    } else if (ident == this._JFXX_IDENT) {
		/* Don't handle JFXX Ident yet */
	    } else {
		/* Don't know about other idents */
	    }
	};

	/* Handle app1 segments */
	this.JpegMeta.JpegFile.prototype._app1Handler = function _app1Handler(mark, pos) {
	    var ident = this._binary_data.slice(pos, pos + 5);
	    if (ident == this._EXIF_IDENT) {
		this._exifHandler(mark, pos + 6);
	    } else {
		/* Don't know about other idents */
	    }
	};

	/* Handle exif segments */
	JpegMeta.JpegFile.prototype._exifHandler = function _exifHandler(mark, pos) {
	    if (this.exif !== undefined) {
		throw new Error("Multiple JFIF segments found");
	    }
	    
	    /* Parse this TIFF header */
	    var endian;
	    var magic_field;
	    var ifd_offset;
	    var primary_ifd, exif_ifd, gps_ifd;
	    var endian_field = this._binary_data.slice(pos, pos + 2);
	    
	    /* Trivia: This 'I' is for Intel, the 'M' is for Motorola */
	    if (endian_field === "II") {
		endian = "<";
	    } else if (endian_field === "MM") {
		endian = ">";
	    } else {
		throw new Error("Malformed TIFF meta-data. Unknown endianess: " + endian_field);
	    }
	    
	    magic_field = JpegMeta.parseNum(endian, this._binary_data, pos + 2, 2);
	    
	    if (magic_field !== 42) {
		throw new Error("Malformed TIFF meta-data. Bad magic: " + magic_field);
	    }
	    
	    ifd_offset = JpegMeta.parseNum(endian, this._binary_data, pos + 4, 4);
	    
	    /* Parse 0th IFD */
	    this._parseIfd(endian, this._binary_data, pos, ifd_offset, this._tifftags, "tiff", "TIFF");
	    
	    if (this.tiff.ExifIfdPointer) {
		this._parseIfd(endian, this._binary_data, pos, this.tiff.ExifIfdPointer.value, this._exiftags, "exif", "Exif");
	    }
	    
	    if (this.tiff.GPSInfoIfdPointer) {
		this._parseIfd(endian, this._binary_data, pos, this.tiff.GPSInfoIfdPointer.value, this._gpstags, "gps", "GPS");
		if (this.gps.GPSLatitude) {
		    var latitude;
		    latitude = this.gps.GPSLatitude.value[0].asFloat() + 
			(1 / 60) * this.gps.GPSLatitude.value[1].asFloat() + 
			(1 / 3600) * this.gps.GPSLatitude.value[2].asFloat();
		    if (this.gps.GPSLatitudeRef.value === "S") {
			latitude = -latitude;
		    }
		    this.gps._addProperty("latitude", "Dec. Latitude", latitude);
		}
		if (this.gps.GPSLongitude) {
		    var longitude;
		    longitude = this.gps.GPSLongitude.value[0].asFloat() + 
			(1 / 60) * this.gps.GPSLongitude.value[1].asFloat() + 
			(1 / 3600) * this.gps.GPSLongitude.value[2].asFloat();
		    if (this.gps.GPSLongitudeRef.value === "W") {
			longitude = -longitude;
		    }
		    this.gps._addProperty("longitude", "Dec. Longitude", longitude);
		}
	    }
	};
	
	/* JsJpegMeta ends here */

	mw.libs.jpegmeta = function( fileReaderResult, fileName ) {
		return new JpegMeta.JpegFile( fileReaderResult, fileName );
	};

} )( jQuery );