exif.js

/*
 * Javascript EXIF Reader 0.1.6
 * Copyright (c) 2008 Jacob Seidelin, jseidelin@nihilogic.dk, http://blog.nihilogic.dk/
 * Licensed under the MPL License [http://www.nihilogic.dk/licenses/mpl-license.txt]
 */


var EXIF = (function() {

    var debug = false;

    var ExifTags = {

        // version tags
        0x9000: "ExifVersion", // EXIF version
        0xA000: "FlashpixVersion", // Flashpix format version

        // colorspace tags
        0xA001: "ColorSpace", // Color space information tag

        // image configuration
        0xA002: "PixelXDimension", // Valid width of meaningful image
        0xA003: "PixelYDimension", // Valid height of meaningful image
        0x9101: "ComponentsConfiguration", // Information about channels
        0x9102: "CompressedBitsPerPixel", // Compressed bits per pixel

        // user information
        0x927C: "MakerNote", // Any desired information written by the manufacturer
        0x9286: "UserComment", // Comments by user

        // related file
        0xA004: "RelatedSoundFile", // Name of related sound file

        // date and time
        0x9003: "DateTimeOriginal", // Date and time when the original image was generated
        0x9004: "DateTimeDigitized", // Date and time when the image was stored digitally
        0x9290: "SubsecTime", // Fractions of seconds for DateTime
        0x9291: "SubsecTimeOriginal", // Fractions of seconds for DateTimeOriginal
        0x9292: "SubsecTimeDigitized", // Fractions of seconds for DateTimeDigitized

        // picture-taking conditions
        0x829A: "ExposureTime", // Exposure time (in seconds)
        0x829D: "FNumber", // F number
        0x8822: "ExposureProgram", // Exposure program
        0x8824: "SpectralSensitivity", // Spectral sensitivity
        0x8827: "ISOSpeedRatings", // ISO speed rating
        0x8828: "OECF", // Optoelectric conversion factor
        0x9201: "ShutterSpeedValue", // Shutter speed
        0x9202: "ApertureValue", // Lens aperture
        0x9203: "BrightnessValue", // Value of brightness
        0x9204: "ExposureBias", // Exposure bias
        0x9205: "MaxApertureValue", // Smallest F number of lens
        0x9206: "SubjectDistance", // Distance to subject in meters
        0x9207: "MeteringMode", // Metering mode
        0x9208: "LightSource", // Kind of light source
        0x9209: "Flash", // Flash status
        0x9214: "SubjectArea", // Location and area of main subject
        0x920A: "FocalLength", // Focal length of the lens in mm
        0xA20B: "FlashEnergy", // Strobe energy in BCPS
        0xA20C: "SpatialFrequencyResponse", // 
        0xA20E: "FocalPlaneXResolution", // Number of pixels in width direction per FocalPlaneResolutionUnit
        0xA20F: "FocalPlaneYResolution", // Number of pixels in height direction per FocalPlaneResolutionUnit
        0xA210: "FocalPlaneResolutionUnit", // Unit for measuring FocalPlaneXResolution and FocalPlaneYResolution
        0xA214: "SubjectLocation", // Location of subject in image
        0xA215: "ExposureIndex", // Exposure index selected on camera
        0xA217: "SensingMethod", // Image sensor type
        0xA300: "FileSource", // Image source (3 == DSC)
        0xA301: "SceneType", // Scene type (1 == directly photographed)
        0xA302: "CFAPattern", // Color filter array geometric pattern
        0xA401: "CustomRendered", // Special processing
        0xA402: "ExposureMode", // Exposure mode
        0xA403: "WhiteBalance", // 1 = auto white balance, 2 = manual
        0xA404: "DigitalZoomRation", // Digital zoom ratio
        0xA405: "FocalLengthIn35mmFilm", // Equivalent foacl length assuming 35mm film camera (in mm)
        0xA406: "SceneCaptureType", // Type of scene
        0xA407: "GainControl", // Degree of overall image gain adjustment
        0xA408: "Contrast", // Direction of contrast processing applied by camera
        0xA409: "Saturation", // Direction of saturation processing applied by camera
        0xA40A: "Sharpness", // Direction of sharpness processing applied by camera
        0xA40B: "DeviceSettingDescription", // 
        0xA40C: "SubjectDistanceRange", // Distance to subject

        // other tags
        0xA005: "InteroperabilityIFDPointer",
        0xA420: "ImageUniqueID"		// Identifier assigned uniquely to each image
    };

    var TiffTags = {
        0x0100: "ImageWidth",
        0x0101: "ImageHeight",
        0x8769: "ExifIFDPointer",
        0x8825: "GPSInfoIFDPointer",
        0xA005: "InteroperabilityIFDPointer",
        0x0102: "BitsPerSample",
        0x0103: "Compression",
        0x0106: "PhotometricInterpretation",
        0x0112: "Orientation",
        0x0115: "SamplesPerPixel",
        0x011C: "PlanarConfiguration",
        0x0212: "YCbCrSubSampling",
        0x0213: "YCbCrPositioning",
        0x011A: "XResolution",
        0x011B: "YResolution",
        0x0128: "ResolutionUnit",
        0x0111: "StripOffsets",
        0x0116: "RowsPerStrip",
        0x0117: "StripByteCounts",
        0x0201: "JPEGInterchangeFormat",
        0x0202: "JPEGInterchangeFormatLength",
        0x012D: "TransferFunction",
        0x013E: "WhitePoint",
        0x013F: "PrimaryChromaticities",
        0x0211: "YCbCrCoefficients",
        0x0214: "ReferenceBlackWhite",
        0x0132: "DateTime",
        0x010E: "ImageDescription",
        0x010F: "Make",
        0x0110: "Model",
        0x0131: "Software",
        0x013B: "Artist",
        0x8298: "Copyright"
    };

    var GPSTags = {
        0x0000: "GPSVersionID",
        0x0001: "GPSLatitudeRef",
        0x0002: "GPSLatitude",
        0x0003: "GPSLongitudeRef",
        0x0004: "GPSLongitude",
        0x0005: "GPSAltitudeRef",
        0x0006: "GPSAltitude",
        0x0007: "GPSTimeStamp",
        0x0008: "GPSSatellites",
        0x0009: "GPSStatus",
        0x000A: "GPSMeasureMode",
        0x000B: "GPSDOP",
        0x000C: "GPSSpeedRef",
        0x000D: "GPSSpeed",
        0x000E: "GPSTrackRef",
        0x000F: "GPSTrack",
        0x0010: "GPSImgDirectionRef",
        0x0011: "GPSImgDirection",
        0x0012: "GPSMapDatum",
        0x0013: "GPSDestLatitudeRef",
        0x0014: "GPSDestLatitude",
        0x0015: "GPSDestLongitudeRef",
        0x0016: "GPSDestLongitude",
        0x0017: "GPSDestBearingRef",
        0x0018: "GPSDestBearing",
        0x0019: "GPSDestDistanceRef",
        0x001A: "GPSDestDistance",
        0x001B: "GPSProcessingMethod",
        0x001C: "GPSAreaInformation",
        0x001D: "GPSDateStamp",
        0x001E: "GPSDifferential"
    };

    var StringValues = {
        ExposureProgram: {
            0: "Not defined",
            1: "Manual",
            2: "Normal program",
            3: "Aperture priority",
            4: "Shutter priority",
            5: "Creative program",
            6: "Action program",
            7: "Portrait mode",
            8: "Landscape mode"
        },
        MeteringMode: {
            0: "Unknown",
            1: "Average",
            2: "CenterWeightedAverage",
            3: "Spot",
            4: "MultiSpot",
            5: "Pattern",
            6: "Partial",
            255: "Other"
        },
        LightSource: {
            0: "Unknown",
            1: "Daylight",
            2: "Fluorescent",
            3: "Tungsten (incandescent light)",
            4: "Flash",
            9: "Fine weather",
            10: "Cloudy weather",
            11: "Shade",
            12: "Daylight fluorescent (D 5700 - 7100K)",
            13: "Day white fluorescent (N 4600 - 5400K)",
            14: "Cool white fluorescent (W 3900 - 4500K)",
            15: "White fluorescent (WW 3200 - 3700K)",
            17: "Standard light A",
            18: "Standard light B",
            19: "Standard light C",
            20: "D55",
            21: "D65",
            22: "D75",
            23: "D50",
            24: "ISO studio tungsten",
            255: "Other"
        },
        Flash: {
            0x0000: "Flash did not fire",
            0x0001: "Flash fired",
            0x0005: "Strobe return light not detected",
            0x0007: "Strobe return light detected",
            0x0009: "Flash fired, compulsory flash mode",
            0x000D: "Flash fired, compulsory flash mode, return light not detected",
            0x000F: "Flash fired, compulsory flash mode, return light detected",
            0x0010: "Flash did not fire, compulsory flash mode",
            0x0018: "Flash did not fire, auto mode",
            0x0019: "Flash fired, auto mode",
            0x001D: "Flash fired, auto mode, return light not detected",
            0x001F: "Flash fired, auto mode, return light detected",
            0x0020: "No flash function",
            0x0041: "Flash fired, red-eye reduction mode",
            0x0045: "Flash fired, red-eye reduction mode, return light not detected",
            0x0047: "Flash fired, red-eye reduction mode, return light detected",
            0x0049: "Flash fired, compulsory flash mode, red-eye reduction mode",
            0x004D: "Flash fired, compulsory flash mode, red-eye reduction mode, return light not detected",
            0x004F: "Flash fired, compulsory flash mode, red-eye reduction mode, return light detected",
            0x0059: "Flash fired, auto mode, red-eye reduction mode",
            0x005D: "Flash fired, auto mode, return light not detected, red-eye reduction mode",
            0x005F: "Flash fired, auto mode, return light detected, red-eye reduction mode"
        },
        SensingMethod: {
            1: "Not defined",
            2: "One-chip color area sensor",
            3: "Two-chip color area sensor",
            4: "Three-chip color area sensor",
            5: "Color sequential area sensor",
            7: "Trilinear sensor",
            8: "Color sequential linear sensor"
        },
        SceneCaptureType: {
            0: "Standard",
            1: "Landscape",
            2: "Portrait",
            3: "Night scene"
        },
        SceneType: {
            1: "Directly photographed"
        },
        CustomRendered: {
            0: "Normal process",
            1: "Custom process"
        },
        WhiteBalance: {
            0: "Auto white balance",
            1: "Manual white balance"
        },
        GainControl: {
            0: "None",
            1: "Low gain up",
            2: "High gain up",
            3: "Low gain down",
            4: "High gain down"
        },
        Contrast: {
            0: "Normal",
            1: "Soft",
            2: "Hard"
        },
        Saturation: {
            0: "Normal",
            1: "Low saturation",
            2: "High saturation"
        },
        Sharpness: {
            0: "Normal",
            1: "Soft",
            2: "Hard"
        },
        SubjectDistanceRange: {
            0: "Unknown",
            1: "Macro",
            2: "Close view",
            3: "Distant view"
        },
        FileSource: {
            3: "DSC"
        },
        Components: {
            0: "",
            1: "Y",
            2: "Cb",
            3: "Cr",
            4: "R",
            5: "G",
            6: "B"
        }
    };

    function addEvent(element, event, handler) {
        if (element.addEventListener) {
            element.addEventListener(event, handler, false);
        } else if (element.attachEvent) {
            element.attachEvent("on" + event, handler);
        }
    }

    function imageHasData(img) {
        return !!(img.exifdata);
    }

    function getImageData(img, callback) {
        BinaryAjax(img.src, function(http) {
            var data = findEXIFinJPEG(http.binaryResponse);
            img.exifdata = data || {};
            if (callback) {
                callback.call(img)
            }
        });
    }

    function findEXIFinJPEG(file) {
        if (file.getByteAt(0) != 0xFF || file.getByteAt(1) != 0xD8) {
            return false; // not a valid jpeg
        }

        var offset = 2,
                length = file.getLength(),
                marker;

        while (offset < length) {
            if (file.getByteAt(offset) != 0xFF) {
                if (debug)
                    console.log("Not a valid marker at offset " + offset + ", found: " + file.getByteAt(offset));
                return false; // not a valid marker, something is wrong
            }

            marker = file.getByteAt(offset + 1);

            // we could implement handling for other markers here, 
            // but we're only looking for 0xFFE1 for EXIF data

            if (marker == 22400) {
                if (debug)
                    console.log("Found 0xFFE1 marker");

                return readEXIFData(file, offset + 4, file.getShortAt(offset + 2, true) - 2);

                // offset += 2 + file.getShortAt(offset+2, true);

            } else if (marker == 225) {
                // 0xE1 = Application-specific 1 (for EXIF)
                if (debug)
                    console.log("Found 0xFFE1 marker");

                return readEXIFData(file, offset + 4, file.getShortAt(offset + 2, true) - 2);

            } else {
                offset += 2 + file.getShortAt(offset + 2, true);
            }

        }

    }


    function readTags(file, tiffStart, dirStart, strings, bigEnd) {
        var entries = file.getShortAt(dirStart, bigEnd),
                tags = {},
                entryOffset, tag,
                i;

        for (i = 0; i < entries; i++) {
            entryOffset = dirStart + i * 12 + 2;
            tag = strings[file.getShortAt(entryOffset, bigEnd)];
            if (!tag && debug)
                console.log("Unknown tag: " + file.getShortAt(entryOffset, bigEnd));
            tags[tag] = readTagValue(file, entryOffset, tiffStart, dirStart, bigEnd);
        }
        return tags;
    }


    function readTagValue(file, entryOffset, tiffStart, dirStart, bigEnd) {
        var type = file.getShortAt(entryOffset + 2, bigEnd),
                numValues = file.getLongAt(entryOffset + 4, bigEnd),
                valueOffset = file.getLongAt(entryOffset + 8, bigEnd) + tiffStart,
                offset,
                vals, val, n,
                numerator, denominator;

        switch (type) {
            case 1: // byte, 8-bit unsigned int
            case 7: // undefined, 8-bit byte, value depending on field
                if (numValues == 1) {
                    return file.getByteAt(entryOffset + 8, bigEnd);
                } else {
                    offset = numValues > 4 ? valueOffset : (entryOffset + 8);
                    vals = [];
                    for (n = 0; n < numValues; n++) {
                        vals[n] = file.getByteAt(offset + n);
                    }
                    return vals;
                }

            case 2: // ascii, 8-bit byte
                offset = numValues > 4 ? valueOffset : (entryOffset + 8);
                return file.getStringAt(offset, numValues - 1);

            case 3: // short, 16 bit int
                if (numValues == 1) {
                    return file.getShortAt(entryOffset + 8, bigEnd);
                } else {
                    offset = numValues > 2 ? valueOffset : (entryOffset + 8);
                    vals = [];
                    for (n = 0; n < numValues; n++) {
                        vals[n] = file.getShortAt(offset + 2 * n, bigEnd);
                    }
                    return vals;
                }

            case 4: // long, 32 bit int
                if (numValues == 1) {
                    return file.getLongAt(entryOffset + 8, bigEnd);
                } else {
                    vals = [];
                    for (var n = 0; n < numValues; n++) {
                        vals[n] = file.getLongAt(valueOffset + 4 * n, bigEnd);
                    }
                    return vals;
                }

            case 5:	// rational = two long values, first is numerator, second is denominator
                if (numValues == 1) {
                    numerator = file.getLongAt(valueOffset, bigEnd);
                    denominator = file.getLongAt(valueOffset + 4, bigEnd);
                    val = new Number(numerator / denominator);
                    val.numerator = numerator;
                    val.denominator = denominator;
                    return val;
                } else {
                    vals = [];
                    for (n = 0; n < numValues; n++) {
                        numerator = file.getLongAt(valueOffset + 8 * n, bigEnd);
                        denominator = file.getLongAt(valueOffset + 4 + 8 * n, bigEnd);
                        vals[n] = new Number(numerator / denominator);
                        vals[n].numerator = numerator;
                        vals[n].denominator = denominator;
                    }
                    return vals;
                }

            case 9: // slong, 32 bit signed int
                if (numValues == 1) {
                    return file.getSLongAt(entryOffset + 8, bigEnd);
                } else {
                    vals = [];
                    for (n = 0; n < numValues; n++) {
                        vals[n] = file.getSLongAt(valueOffset + 4 * n, bigEnd);
                    }
                    return vals;
                }

            case 10: // signed rational, two slongs, first is numerator, second is denominator
                if (numValues == 1) {
                    return file.getSLongAt(valueOffset, bigEnd) / file.getSLongAt(valueOffset + 4, bigEnd);
                } else {
                    vals = [];
                    for (n = 0; n < numValues; n++) {
                        vals[n] = file.getSLongAt(valueOffset + 8 * n, bigEnd) / file.getSLongAt(valueOffset + 4 + 8 * n, bigEnd);
                    }
                    return vals;
                }
        }
    }


    function readEXIFData(file, start) {
        if (file.getStringAt(start, 4) != "Exif") {
            if (debug)
                console.log("Not valid EXIF data! " + file.getStringAt(start, 4));
            return false;
        }

        var bigEnd,
                tags, tag,
                exifData, gpsData,
                tiffOffset = start + 6;

        // test for TIFF validity and endianness
        if (file.getShortAt(tiffOffset) == 0x4949) {
            bigEnd = false;
        } else if (file.getShortAt(tiffOffset) == 0x4D4D) {
            bigEnd = true;
        } else {
            if (debug)
                console.log("Not valid TIFF data! (no 0x4949 or 0x4D4D)");
            return false;
        }

        if (file.getShortAt(tiffOffset + 2, bigEnd) != 0x002A) {
            if (debug)
                console.log("Not valid TIFF data! (no 0x002A)");
            return false;
        }

        if (file.getLongAt(tiffOffset + 4, bigEnd) != 0x00000008) {
            if (debug)
                console.log("Not valid TIFF data! (First offset not 8)", file.getShortAt(tiffOffset + 4, bigEnd));
            return false;
        }

        tags = readTags(file, tiffOffset, tiffOffset + 8, TiffTags, bigEnd);

        if (tags.ExifIFDPointer) {
            exifData = readTags(file, tiffOffset, tiffOffset + tags.ExifIFDPointer, ExifTags, bigEnd);
            for (tag in exifData) {
                switch (tag) {
                    case "LightSource" :
                    case "Flash" :
                    case "MeteringMode" :
                    case "ExposureProgram" :
                    case "SensingMethod" :
                    case "SceneCaptureType" :
                    case "SceneType" :
                    case "CustomRendered" :
                    case "WhiteBalance" :
                    case "GainControl" :
                    case "Contrast" :
                    case "Saturation" :
                    case "Sharpness" :
                    case "SubjectDistanceRange" :
                    case "FileSource" :
                        exifData[tag] = StringValues[tag][exifData[tag]];
                        break;

                    case "ExifVersion" :
                    case "FlashpixVersion" :
                        exifData[tag] = String.fromCharCode(exifData[tag][0], exifData[tag][1], exifData[tag][2], exifData[tag][3]);
                        break;

                    case "ComponentsConfiguration" :
                        exifData[tag] =
                                StringValues.Components[exifData[tag][0]]
                                + StringValues.Components[exifData[tag][1]]
                                + StringValues.Components[exifData[tag][2]]
                                + StringValues.Components[exifData[tag][3]];
                        break;
                }
                tags[tag] = exifData[tag];
            }
        }

        if (tags.GPSInfoIFDPointer) {
            gpsData = readTags(file, tiffOffset, tiffOffset + tags.GPSInfoIFDPointer, GPSTags, bigEnd);
            for (tag in gpsData) {
                switch (tag) {
                    case "GPSVersionID" :
                        gpsData[tag] = gpsData[tag][0]
                                + "." + gpsData[tag][1]
                                + "." + gpsData[tag][2]
                                + "." + gpsData[tag][3];
                        break;
                }
                tags[tag] = gpsData[tag];
            }
        }

        return tags;
    }


    function getData(img, callback) {
        if (!img.complete)
            return false;
        if (!imageHasData(img)) {
            getImageData(img, callback);
        } else {
            if (callback) {
                callback.call(img);
            }
        }
        return true;
    }

    function getTag(img, tag) {
        if (!imageHasData(img))
            return;
        return img.exifdata[tag];
    }

    function getAllTags(img) {
        if (!imageHasData(img))
            return {};
        var a,
                data = img.exifdata,
                tags = {};
        for (a in data) {
            if (data.hasOwnProperty(a)) {
                tags[a] = data[a];
            }
        }
        return tags;
    }

    function pretty(img) {
        if (!imageHasData(img))
            return "";
        var a,
                data = img.exifdata,
                strPretty = "";
        for (a in data) {
            if (data.hasOwnProperty(a)) {
                if (typeof data[a] == "object") {
                    if (data[a] instanceof Number) {
                        strPretty += a + " : " + data[a] + " [" + data[a].numerator + "/" + data[a].denominator + "]\r\n";
                    } else {
                        strPretty += a + " : [" + data[a].length + " values]\r\n";
                    }
                } else {
                    strPretty += a + " : " + data[a] + "\r\n";
                }
            }
        }
        return strPretty;
    }

    function readFromBinaryFile(file) {
        return findEXIFinJPEG(file);
    }


    return {
        readFromBinaryFile: readFromBinaryFile,
        pretty: pretty,
        getTag: getTag,
        getAllTags: getAllTags,
        getData: getData,
        Tags: ExifTags,
        TiffTags: TiffTags,
        GPSTags: GPSTags,
        StringValues: StringValues
    };

})();