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

本文实例为大家分享了Vue2.0实现调用摄像头进行拍照功能的具体代码，以及图片上传功能引用exif.js，供大家参考，具体内容如下

可以在github 上下载demo链接

vue组件代码

<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>

引用的exif.js代码

(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 ? valueOffset : (entryOffset + 8);
          vals = [];
          for (n=0;n<numValues;n++) {
            vals[n] = file.getUint8(offset + n);
          }
          return vals;
        }

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

      case 3: // short, 16 bit int
        if (numValues == 1) {
          return file.getUint16(entryOffset + 8, !bigEnd);
        } else {
          offset = numValues > 2 ? valueOffset : (entryOffset + 8);
          vals = [];
          for (n=0;n<numValues;n++) {
            vals[n] = file.getUint16(offset + 2*n, !bigEnd);
          }
          return vals;
        }

      case 4: // long, 32 bit int
        if (numValues == 1) {
          return file.getUint32(entryOffset + 8, !bigEnd);
        } else {
          vals = [];
          for (n=0;n<numValues;n++) {
            vals[n] = file.getUint32(valueOffset + 4*n, !bigEnd);
          }
          return vals;
        }

      case 5:  // rational = two long values, first is numerator, second is denominator
        if (numValues == 1) {
          numerator = file.getUint32(valueOffset, !bigEnd);
          denominator = file.getUint32(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.getUint32(valueOffset + 8*n, !bigEnd);
            denominator = file.getUint32(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.getInt32(entryOffset + 8, !bigEnd);
        } else {
          vals = [];
          for (n=0;n<numValues;n++) {
            vals[n] = file.getInt32(valueOffset + 4*n, !bigEnd);
          }
          return vals;
        }

      case 10: // signed rational, two slongs, first is numerator, second is denominator
        if (numValues == 1) {
          return file.getInt32(valueOffset, !bigEnd) / file.getInt32(valueOffset+4, !bigEnd);
        } else {
          vals = [];
          for (n=0;n<numValues;n++) {
            vals[n] = file.getInt32(valueOffset + 8*n, !bigEnd) / file.getInt32(valueOffset+4 + 8*n, !bigEnd);
          }
          return vals;
        }
    }
  }

  function getStringFromDB(buffer, start, length) {
    var outstr = "";
    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));

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