Vue2.0实现调用摄像头进行拍照功能 exif.js实现图片上传功能

<template>
 <div>
 <div style="padding:20px;">
  <div class="show">
  <div class="picture" :style="'backgroundImage:url('+headerImage+')'"></div>
  </div>
  <div style="margin-top:20px;">
  <input type="file" id="upload" accept="image/jpg" @change="upload">
  <label for="upload"></label>
  </div>
 </div>
 </div>
</template>

<script>
import {Exif} from './exif.js'

export default {
 data () {
 return {
  headerImage:'',picValue:''
 }
 },
 mounted () {
 },
 methods: {
 upload (e) {
  let files = e.target.files || e.dataTransfer.files;
  if (!files.length) return;
  this.picValue = files[0];
  this.imgPreview(this.picValue);
  console.log(this.picValue)
 },
 imgPreview (file) {
  let self = this;
  let Orientation;
  //去获取拍照时的信息，解决拍出来的照片旋转问题
  Exif.getData(file, function(){
   Orientation = Exif.getTag(this, 'Orientation');
  });
  // 看支持不支持FileReader 
  if (!file || !window.FileReader) return;

  if (/^image/.test(file.type)) {
   // 创建一个reader
   let reader = new FileReader();
   // 将图片2将转成 base64 格式
   reader.readAsDataURL(file);
   // 读取成功后的回调
   reader.onloadend = function () {
   let result = this.result;
   let img = new Image();
   img.src = result;
   //判断图片是否大于100K,是就直接上传，反之压缩图片
   if (this.result.length <= (100 * 1024)) {
    self.headerImage = this.result;
    self.postImg();
   }else {
    img.onload = function () {
    let data = self.compress(img,Orientation);
    self.headerImage = data;
    self.postImg();
    }
   }
   }
  }
  },
  postImg () {
  //这里写接口
  },
  rotateImg (img, direction,canvas) {
  //最小与最大旋转方向，图片旋转4次后回到原方向
  const min_step = 0;
  const max_step = 3;
  if (img == null)return;
  //img的高度和宽度不能在img元素隐藏后获取，否则会出错
  let height = img.height;
  let width = img.width;
  let step = 2;
  if (step == null) {
   step = min_step;
  }
  if (direction == 'right') {
   step++;
   //旋转到原位置，即超过最大值
   step > max_step && (step = min_step);
  } else {
   step--;
   step < min_step && (step = max_step);
  }
  //旋转角度以弧度值为参数
  let degree = step * 90 * Math.PI / 180;
  let ctx = canvas.getContext('2d');
  switch (step) {
   case 0:
    canvas.width = width;
    canvas.height = height;
    ctx.drawImage(img, 0, 0);
    break;
   case 1:
    canvas.width = height;
    canvas.height = width;
    ctx.rotate(degree);
    ctx.drawImage(img, 0, -height);
    break;
   case 2:
    canvas.width = width;
    canvas.height = height;
    ctx.rotate(degree);
    ctx.drawImage(img, -width, -height);
    break;
   case 3:
    canvas.width = height;
    canvas.height = width;
    ctx.rotate(degree);
    ctx.drawImage(img, -width, 0);
    break;
  }
 },
 compress(img,Orientation) {
  let canvas = document.createElement("canvas");
  let ctx = canvas.getContext('2d');
  //瓦片canvas
  let tCanvas = document.createElement("canvas");
  let tctx = tCanvas.getContext("2d");
  let initSize = img.src.length;
  let width = img.width;
  let height = img.height;
  //如果图片大于四百万像素，计算压缩比并将大小压至400万以下
  let ratio;
  if ((ratio = width * height / 4000000) > 1) {
  console.log("大于400万像素")
  ratio = Math.sqrt(ratio);
  width /= ratio;
  height /= ratio;
  } else {
  ratio = 1;
  }
  canvas.width = width;
  canvas.height = height;
 //  铺底色
  ctx.fillStyle = "#fff";
  ctx.fillRect(0, 0, canvas.width, canvas.height);
  //如果图片像素大于100万则使用瓦片绘制
  let count;
  if ((count = width * height / 1000000) > 1) {
  console.log("超过100W像素");
  count = ~~(Math.sqrt(count) + 1); //计算要分成多少块瓦片
 //   计算每块瓦片的宽和高
  let nw = ~~(width / count);
  let nh = ~~(height / count);
  tCanvas.width = nw;
  tCanvas.height = nh;
  for (let i = 0; i < count; i++) {
   for (let j = 0; j < count; j++) {
   tctx.drawImage(img, i * nw * ratio, j * nh * ratio, nw * ratio, nh * ratio, 0, 0, nw, nh);
   ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh);
   }
  }
  } else {
  ctx.drawImage(img, 0, 0, width, height);
  }
  //修复ios上传图片的时候 被旋转的问题
  if(Orientation != "" && Orientation != 1){
  switch(Orientation){
   case 6://需要顺时针（向左）90度旋转
    this.rotateImg(img,'left',canvas);
    break;
   case 8://需要逆时针（向右）90度旋转
    this.rotateImg(img,'right',canvas);
    break;
   case 3://需要180度旋转
    this.rotateImg(img,'right',canvas);//转两次
    this.rotateImg(img,'right',canvas);
    break;
  }
  }
  //进行最小压缩
  let ndata = canvas.toDataURL('image/jpeg', 0.1);
  console.log('压缩前：' + initSize);
  console.log('压缩后：' + ndata.length);
  console.log('压缩率：' + ~~(100 * (initSize - ndata.length) / initSize) + "%");
  tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0;
  return ndata;
 },
 }
}
</script>

<style>
*{
 margin: 0;
 padding: 0;
}
.show {
 width: 100px;
 height: 100px;
 overflow: hidden;
 position: relative;
 border-radius: 50%;
 border: 1px solid #d5d5d5;
}
.picture {
 width: 100%;
 height: 100%;
 overflow: hidden;
 background-position: center center;
 background-repeat: no-repeat;
 background-size: cover;
}
</style>

(function() {

 var debug = false;

 var root = this;

 var EXIF = function(obj) {
  if (obj instanceof EXIF) return obj;
  if (!(this instanceof EXIF)) return new EXIF(obj);
  this.EXIFwrapped = obj;
 };

 if (typeof exports !== 'undefined') {
  if (typeof module !== 'undefined' && module.exports) {
   exports = module.exports = EXIF;
  }
  exports.EXIF = EXIF;
 } else {
  root.EXIF = EXIF;
 }

 var ExifTags = EXIF.Tags = {

  // 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 = EXIF.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 = EXIF.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 = EXIF.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 base64ToArrayBuffer(base64, contentType) {
  contentType = contentType || base64.match(/^data\:([^\;]+)\;base64,/mi)[1] || ''; // e.g. 'data:image/jpeg;base64,...' => 'image/jpeg'
  base64 = base64.replace(/^data\:([^\;]+)\;base64,/gmi, '');
  var binary = atob(base64);
  var len = binary.length;
  var buffer = new ArrayBuffer(len);
  var view = new Uint8Array(buffer);
  for (var i = 0; i < len; i++) {
   view[i] = binary.charCodeAt(i);
  }
  return buffer;
 }

 function objectURLToBlob(url, callback) {
  var http = new XMLHttpRequest();
  http.open("GET", url, true);
  http.responseType = "blob";
  http.onload = function(e) {
   if (this.status == 200 || this.status === 0) {
    callback(this.response);
   }
  };
  http.send();
 }

 function getImageData(img, callback) {
  function handleBinaryFile(binFile) {
   var data = findEXIFinJPEG(binFile);
   var iptcdata = findIPTCinJPEG(binFile);
   img.exifdata = data || {};
   img.iptcdata = iptcdata || {};
   if (callback) {
    callback.call(img);
   }
  }

  if (img.src) {
   if (/^data\:/i.test(img.src)) { // Data URI
    var arrayBuffer = base64ToArrayBuffer(img.src);
    handleBinaryFile(arrayBuffer);

   } else if (/^blob\:/i.test(img.src)) { // Object URL
    var fileReader = new FileReader();
    fileReader.onload = function(e) {
     handleBinaryFile(e.target.result);
    };
    objectURLToBlob(img.src, function (blob) {
     fileReader.readAsArrayBuffer(blob);
    });
   } else {
    var http = new XMLHttpRequest();
    http.onload = function() {
     if (this.status == 200 || this.status === 0) {
      handleBinaryFile(http.response);
     } else {
      throw "Could not load image";
     }
     http = null;
    };
    http.open("GET", img.src, true);
    http.responseType = "arraybuffer";
    http.send(null);
   }
  } else if (window.FileReader && (img instanceof window.Blob || img instanceof window.File)) {
   var fileReader = new FileReader();
   fileReader.onload = function(e) {
    if (debug) console.log("Got file of length " + e.target.result.byteLength);
    handleBinaryFile(e.target.result);
   };

   fileReader.readAsArrayBuffer(img);
  }
 }

 function findEXIFinJPEG(file) {
  var dataView = new DataView(file);

  if (debug) console.log("Got file of length " + file.byteLength);
  if ((dataView.getUint8(0) != 0xFF) || (dataView.getUint8(1) != 0xD8)) {
   if (debug) console.log("Not a valid JPEG");
   return false; // not a valid jpeg
  }

  var offset = 2,
   length = file.byteLength,
   marker;

  while (offset < length) {
   if (dataView.getUint8(offset) != 0xFF) {
    if (debug) console.log("Not a valid marker at offset " + offset + ", found: " + dataView.getUint8(offset));
    return false; // not a valid marker, something is wrong
   }

   marker = dataView.getUint8(offset + 1);
   if (debug) console.log(marker);

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

   if (marker == 225) {
    if (debug) console.log("Found 0xFFE1 marker");

    return readEXIFData(dataView, offset + 4, dataView.getUint16(offset + 2) - 2);

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

   } else {
    offset += 2 + dataView.getUint16(offset+2);
   }

  }

 }

 function findIPTCinJPEG(file) {
  var dataView = new DataView(file);

  if (debug) console.log("Got file of length " + file.byteLength);
  if ((dataView.getUint8(0) != 0xFF) || (dataView.getUint8(1) != 0xD8)) {
   if (debug) console.log("Not a valid JPEG");
   return false; // not a valid jpeg
  }

  var offset = 2,
   length = file.byteLength;


  var isFieldSegmentStart = function(dataView, offset){
   return (
    dataView.getUint8(offset) === 0x38 &&
    dataView.getUint8(offset+1) === 0x42 &&
    dataView.getUint8(offset+2) === 0x49 &&
    dataView.getUint8(offset+3) === 0x4D &&
    dataView.getUint8(offset+4) === 0x04 &&
    dataView.getUint8(offset+5) === 0x04
   );
  };

  while (offset < length) {

   if ( isFieldSegmentStart(dataView, offset )){

    // Get the length of the name header (which is padded to an even number of bytes)
    var nameHeaderLength = dataView.getUint8(offset+7);
    if(nameHeaderLength % 2 !== 0) nameHeaderLength += 1;
    // Check for pre photoshop 6 format
    if(nameHeaderLength === 0) {
     // Always 4
     nameHeaderLength = 4;
    }

    var startOffset = offset + 8 + nameHeaderLength;
    var sectionLength = dataView.getUint16(offset + 6 + nameHeaderLength);

    return readIPTCData(file, startOffset, sectionLength);

    break;

   }


   // Not the marker, continue searching
   offset++;

  }

 }
 var IptcFieldMap = {
  0x78 : 'caption',
  0x6E : 'credit',
  0x19 : 'keywords',
  0x37 : 'dateCreated',
  0x50 : 'byline',
  0x55 : 'bylineTitle',
  0x7A : 'captionWriter',
  0x69 : 'headline',
  0x74 : 'copyright',
  0x0F : 'category'
 };
 function readIPTCData(file, startOffset, sectionLength){
  var dataView = new DataView(file);
  var data = {};
  var fieldValue, fieldName, dataSize, segmentType, segmentSize;
  var segmentStartPos = startOffset;
  while(segmentStartPos < startOffset+sectionLength) {
   if(dataView.getUint8(segmentStartPos) === 0x1C && dataView.getUint8(segmentStartPos+1) === 0x02){
    segmentType = dataView.getUint8(segmentStartPos+2);
    if(segmentType in IptcFieldMap) {
     dataSize = dataView.getInt16(segmentStartPos+3);
     segmentSize = dataSize + 5;
     fieldName = IptcFieldMap[segmentType];
     fieldValue = getStringFromDB(dataView, segmentStartPos+5, dataSize);
     // Check if we already stored a value with this name
     if(data.hasOwnProperty(fieldName)) {
      // Value already stored with this name, create multivalue field
      if(data[fieldName] instanceof Array) {
       data[fieldName].push(fieldValue);
      }
      else {
       data[fieldName] = [data[fieldName], fieldValue];
      }
     }
     else {
      data[fieldName] = fieldValue;
     }
    }

   }
   segmentStartPos++;
  }
  return data;
 }



 function readTags(file, tiffStart, dirStart, strings, bigEnd) {
  var entries = file.getUint16(dirStart, !bigEnd),
   tags = {},
   entryOffset, tag,
   i;

  for (i=0;i<entries;i++) {
   entryOffset = dirStart + i*12 + 2;
   tag = strings[file.getUint16(entryOffset, !bigEnd)];
   if (!tag && debug) console.log("Unknown tag: " + file.getUint16(entryOffset, !bigEnd));
   tags[tag] = readTagValue(file, entryOffset, tiffStart, dirStart, bigEnd);
  }
  return tags;
 }


 function readTagValue(file, entryOffset, tiffStart, dirStart, bigEnd) {
  var type = file.getUint16(entryOffset+2, !bigEnd),
   numValues = file.getUint32(entryOffset+4, !bigEnd),
   valueOffset = file.getUint32(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.getUint8(entryOffset + 8, !bigEnd);
    } else {
     offset = numValues > 4 "";
  for (n = start; n < start+length; n++) {
   outstr += String.fromCharCode(buffer.getUint8(n));
  }
  return outstr;
 }

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

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

  // test for TIFF validity and endianness
  if (file.getUint16(tiffOffset) == 0x4949) {
   bigEnd = false;
  } else if (file.getUint16(tiffOffset) == 0x4D4D) {
   bigEnd = true;
  } else {
   if (debug) console.log("Not valid TIFF data! (no 0x4949 or 0x4D4D)");
   return false;
  }

  if (file.getUint16(tiffOffset+2, !bigEnd) != 0x002A) {
   if (debug) console.log("Not valid TIFF data! (no 0x002A)");
   return false;
  }

  var firstIFDOffset = file.getUint32(tiffOffset+4, !bigEnd);

  if (firstIFDOffset < 0x00000008) {
   if (debug) console.log("Not valid TIFF data! (First offset less than 8)", file.getUint32(tiffOffset+4, !bigEnd));
   return false;
  }

  tags = readTags(file, tiffOffset, tiffOffset + firstIFDOffset, 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;
 }

 EXIF.getData = function(img, callback) {
  if ((img instanceof Image || img instanceof HTMLImageElement) && !img.complete) return false;

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

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

 EXIF.getAllTags = function(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;
 }

 EXIF.pretty = function(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;
 }

 EXIF.readFromBinaryFile = function(file) {
  return findEXIFinJPEG(file);
 }

 if (typeof define === 'function' && define.amd) {
  define('exif-js', [], function() {
   return EXIF;
  });
 }
}.call(this));