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易焱
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/**
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* 代码来自于：https://github.com/blueimp/JavaScript-Load-Image
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* 暂时项目中只用了orientation.
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*
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* 去除了 Exif Sub IFD Pointer, GPS Info IFD Pointer, Exif Thumbnail.
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* @fileOverview EXIF解析
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*/
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// Sample
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// ====================================
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// Make : Apple
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// Model : iPhone 4S
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// Orientation : 1
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// XResolution : 72 [72/1]
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// YResolution : 72 [72/1]
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// ResolutionUnit : 2
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// Software : QuickTime 7.7.1
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// DateTime : 2013:09:01 22:53:55
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// ExifIFDPointer : 190
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// ExposureTime : 0.058823529411764705 [1/17]
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// FNumber : 2.4 [12/5]
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// ExposureProgram : Normal program
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// ISOSpeedRatings : 800
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// ExifVersion : 0220
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// DateTimeOriginal : 2013:09:01 22:52:51
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// DateTimeDigitized : 2013:09:01 22:52:51
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// ComponentsConfiguration : YCbCr
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// ShutterSpeedValue : 4.058893515764426
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// ApertureValue : 2.5260688216892597 [4845/1918]
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// BrightnessValue : -0.3126686601998395
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// MeteringMode : Pattern
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// Flash : Flash did not fire, compulsory flash mode
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// FocalLength : 4.28 [107/25]
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// SubjectArea : [4 values]
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// FlashpixVersion : 0100
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// ColorSpace : 1
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// PixelXDimension : 2448
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// PixelYDimension : 3264
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// SensingMethod : One-chip color area sensor
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// ExposureMode : 0
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// WhiteBalance : Auto white balance
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// FocalLengthIn35mmFilm : 35
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// SceneCaptureType : Standard
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define([
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'../../../base',
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'../imagemeta'
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], function( Base, ImageMeta ) {
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var EXIF = {};
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EXIF.ExifMap = function() {
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return this;
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};
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EXIF.ExifMap.prototype.map = {
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'Orientation': 0x0112
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};
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EXIF.ExifMap.prototype.get = function( id ) {
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return this[ id ] || this[ this.map[ id ] ];
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};
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EXIF.exifTagTypes = {
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// byte, 8-bit unsigned int:
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1: {
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getValue: function( dataView, dataOffset ) {
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return dataView.getUint8( dataOffset );
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},
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size: 1
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},
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// ascii, 8-bit byte:
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2: {
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getValue: function( dataView, dataOffset ) {
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return String.fromCharCode( dataView.getUint8( dataOffset ) );
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},
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size: 1,
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ascii: true
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},
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// short, 16 bit int:
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3: {
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getValue: function( dataView, dataOffset, littleEndian ) {
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return dataView.getUint16( dataOffset, littleEndian );
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},
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size: 2
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},
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// long, 32 bit int:
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4: {
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getValue: function( dataView, dataOffset, littleEndian ) {
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return dataView.getUint32( dataOffset, littleEndian );
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},
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size: 4
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},
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// rational = two long values,
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// first is numerator, second is denominator:
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5: {
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getValue: function( dataView, dataOffset, littleEndian ) {
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return dataView.getUint32( dataOffset, littleEndian ) /
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dataView.getUint32( dataOffset + 4, littleEndian );
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},
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size: 8
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},
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// slong, 32 bit signed int:
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9: {
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getValue: function( dataView, dataOffset, littleEndian ) {
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return dataView.getInt32( dataOffset, littleEndian );
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},
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size: 4
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},
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// srational, two slongs, first is numerator, second is denominator:
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10: {
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getValue: function( dataView, dataOffset, littleEndian ) {
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return dataView.getInt32( dataOffset, littleEndian ) /
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dataView.getInt32( dataOffset + 4, littleEndian );
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},
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size: 8
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}
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};
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// undefined, 8-bit byte, value depending on field:
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EXIF.exifTagTypes[ 7 ] = EXIF.exifTagTypes[ 1 ];
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EXIF.getExifValue = function( dataView, tiffOffset, offset, type, length,
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littleEndian ) {
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var tagType = EXIF.exifTagTypes[ type ],
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tagSize, dataOffset, values, i, str, c;
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if ( !tagType ) {
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Base.log('Invalid Exif data: Invalid tag type.');
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return;
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}
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tagSize = tagType.size * length;
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// Determine if the value is contained in the dataOffset bytes,
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// or if the value at the dataOffset is a pointer to the actual data:
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dataOffset = tagSize > 4 ? tiffOffset + dataView.getUint32( offset + 8,
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littleEndian ) : (offset + 8);
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if ( dataOffset + tagSize > dataView.byteLength ) {
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Base.log('Invalid Exif data: Invalid data offset.');
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return;
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}
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if ( length === 1 ) {
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return tagType.getValue( dataView, dataOffset, littleEndian );
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}
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values = [];
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for ( i = 0; i < length; i += 1 ) {
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values[ i ] = tagType.getValue( dataView,
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dataOffset + i * tagType.size, littleEndian );
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}
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if ( tagType.ascii ) {
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str = '';
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// Concatenate the chars:
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for ( i = 0; i < values.length; i += 1 ) {
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c = values[ i ];
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// Ignore the terminating NULL byte(s):
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if ( c === '\u0000' ) {
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break;
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}
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str += c;
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}
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return str;
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}
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return values;
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};
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EXIF.parseExifTag = function( dataView, tiffOffset, offset, littleEndian,
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data ) {
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var tag = dataView.getUint16( offset, littleEndian );
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data.exif[ tag ] = EXIF.getExifValue( dataView, tiffOffset, offset,
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dataView.getUint16( offset + 2, littleEndian ), // tag type
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dataView.getUint32( offset + 4, littleEndian ), // tag length
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littleEndian );
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};
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EXIF.parseExifTags = function( dataView, tiffOffset, dirOffset,
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littleEndian, data ) {
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var tagsNumber, dirEndOffset, i;
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if ( dirOffset + 6 > dataView.byteLength ) {
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Base.log('Invalid Exif data: Invalid directory offset.');
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return;
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}
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tagsNumber = dataView.getUint16( dirOffset, littleEndian );
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dirEndOffset = dirOffset + 2 + 12 * tagsNumber;
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if ( dirEndOffset + 4 > dataView.byteLength ) {
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Base.log('Invalid Exif data: Invalid directory size.');
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return;
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}
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for ( i = 0; i < tagsNumber; i += 1 ) {
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this.parseExifTag( dataView, tiffOffset,
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dirOffset + 2 + 12 * i, // tag offset
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littleEndian, data );
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}
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// Return the offset to the next directory:
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return dataView.getUint32( dirEndOffset, littleEndian );
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};
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// EXIF.getExifThumbnail = function(dataView, offset, length) {
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// var hexData,
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// i,
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// b;
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// if (!length || offset + length > dataView.byteLength) {
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// Base.log('Invalid Exif data: Invalid thumbnail data.');
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// return;
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// }
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// hexData = [];
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// for (i = 0; i < length; i += 1) {
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// b = dataView.getUint8(offset + i);
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// hexData.push((b < 16 ? '0' : '') + b.toString(16));
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// }
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// return 'data:image/jpeg,%' + hexData.join('%');
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// };
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EXIF.parseExifData = function( dataView, offset, length, data ) {
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var tiffOffset = offset + 10,
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littleEndian, dirOffset;
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// Check for the ASCII code for "Exif" (0x45786966):
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if ( dataView.getUint32( offset + 4 ) !== 0x45786966 ) {
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// No Exif data, might be XMP data instead
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return;
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}
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if ( tiffOffset + 8 > dataView.byteLength ) {
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Base.log('Invalid Exif data: Invalid segment size.');
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return;
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}
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// Check for the two null bytes:
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if ( dataView.getUint16( offset + 8 ) !== 0x0000 ) {
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Base.log('Invalid Exif data: Missing byte alignment offset.');
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return;
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}
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// Check the byte alignment:
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switch ( dataView.getUint16( tiffOffset ) ) {
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case 0x4949:
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littleEndian = true;
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break;
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case 0x4D4D:
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littleEndian = false;
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break;
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default:
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Base.log('Invalid Exif data: Invalid byte alignment marker.');
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return;
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}
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// Check for the TIFF tag marker (0x002A):
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if ( dataView.getUint16( tiffOffset + 2, littleEndian ) !== 0x002A ) {
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Base.log('Invalid Exif data: Missing TIFF marker.');
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return;
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}
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// Retrieve the directory offset bytes, usually 0x00000008 or 8 decimal:
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dirOffset = dataView.getUint32( tiffOffset + 4, littleEndian );
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// Create the exif object to store the tags:
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data.exif = new EXIF.ExifMap();
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// Parse the tags of the main image directory and retrieve the
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// offset to the next directory, usually the thumbnail directory:
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dirOffset = EXIF.parseExifTags( dataView, tiffOffset,
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tiffOffset + dirOffset, littleEndian, data );
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// 尝试读取缩略图
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// if ( dirOffset ) {
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// thumbnailData = {exif: {}};
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// dirOffset = EXIF.parseExifTags(
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// dataView,
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// tiffOffset,
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// tiffOffset + dirOffset,
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// littleEndian,
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// thumbnailData
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// );
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// // Check for JPEG Thumbnail offset:
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// if (thumbnailData.exif[0x0201]) {
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// data.exif.Thumbnail = EXIF.getExifThumbnail(
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// dataView,
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// tiffOffset + thumbnailData.exif[0x0201],
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// thumbnailData.exif[0x0202] // Thumbnail data length
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// );
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// }
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// }
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};
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ImageMeta.parsers[ 0xffe1 ].push( EXIF.parseExifData );
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return EXIF;
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});
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