上传图片的时候,ios手机的图片会旋转90°

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1、问题:在html5中利用canvas对上传图片压缩的时候,ios手机竖着拍照时,图片会旋转90°,其他情况正常。

2、解决方法获取拍照角度,对Ios竖着拍的照片进行角度处理

3、利用exif.js获取到照片的拍摄信息,这里主要用到Orientation,这个属性

Orientation      旋转角度

     1             0°

     3            180°

     6             90°

     8            270°

旋转方向都为顺时针

下面介绍图片的压缩和对ios拍照问题的解决案例

先要引入exif.js文件和jquery.js文件

<script src="http://i.gtimg.cn/qzone/biz/gdt/lib/jquery/jquery-2.1.4.js?max_age=31536000"></script>
<script type="text/javascript" src='js/exif.js?v=b5d2a25070'></script>


4、html

<input type="file" id="upLoad" name="image">
<!-- 显示上传之后的图片 -->
<div id='previewImg'>
    <img id='viewImg'/>
</div>

5、js

 $('#upLoad').on('change',function(){
        $('#loding').css('display','block');
        var filePath = $(this).val(),//获取到input的value,里面是文件的路径
            fileFormat = filePath.substring(filePath.lastIndexOf(".")).toLowerCase(),// src = '',//转成可以在本地预览的blob格式
            imgBase64 = '',//存储图片的imgBase64
            fileObj = document.getElementById('upLoad').files[0];       //上传文件的对象,要这样写才行,用jquery写法获取不到对象
            uploadAddress = globalConfig.pre_api_url + '/wxwall_api/msg/pa_upload_img.PHP',data = null;
            
        // 检查是否是图片
        if( !fileFormat.match(/.png|.jpg|.jpeg/) ) {
            error_prompt_alert('上传错误,文件格式必须为:png/jpg/jpeg');
            $('#loding').css('display','none');
            return;  
        }

        // 对图片进行压缩
        compress(fileObj,function(imgBase64){
            imgBase64 = imgBase64;
           
            // 对图片压缩成功之后,在定义上传参数,和请求;放在compress()外面的话,则先执行request()请求,此时imgBase64还未赋值赋值
            // 定义上传的参数
            data = {
                'imgBase64':imgBase64,'openid':openid
            };

            // 发送上传图片的请求
            request(uploadAddress,data,function(res){
                console.log(res.msg);
                $('#loding').css('display','none');
                remote_pa_img_path = res.data.remote_pa_img_path;
                $('#viewImg').attr('src',imgBase64); //显示预览图片
                $('#imgBox').addClass('imgBox2');
            },'none');
            });
        });       
    });

    // 不对图片进行压缩,直接转成base64
    function directTurnIntoBase64(fileObj,callback){
        var r = new FileReader();
        // 转成base64
        r.onload = function(){
           //变成字符串
            imgBase64 = r.result;
            console.log(imgBase64);
            callback(imgBase64);
        }
        r.readAsDataURL(fileObj);    //转成Base64格式
    }

    // 对图片进行压缩
    function compress(fileObj,callback) { 
        if ( typeof (FileReader) === 'undefined') {  
            console.log("当前浏览器内核不支持base64图标压缩");  
            //调用上传方式不压缩  
            directTurnIntoBase64(fileObj,callback);
        } else {  
            try {    
                var Orientation=null,reader = new FileReader();  
                // reader.readAsDataURL(fileObj);  

                //获取图片Orientation参数
                EXIF.getData(fileObj,function() {
                    Orientation = EXIF.getTag(this,'Orientation');
                });

                reader.onload = function (e) {  
                    var image = $('<img/>'); 
                    image.attr('src',e.target.result);  
                    image.load(function(){  
                        var data='',canvas = document.createElement('canvas'),context = canvas.getContext('2d'),imageWidth = this.width,imageHeight = this.height;


                        //压缩图片
                        if(imageWidth > 1000 || imageHeight > 1000) {
                             //等比例压缩,不失真,不裁剪
                            if( imageWidth > imageHeight){
                                imageWidth = 1000;
                                imageHeight = imageWidth*imageHeight/this.width;
                            }else{
                                imageHeight = 1000;
                                imageWidth = imageHeight*imageWidth/this.height;
                            }
                        }

                        //旋转到正常角度,位置偏移
                        var angle = 0;
                        var x =0,y=0,w=imageWidth,h=imageHeight;   //canvas画布
                        // 定义画布的大小
                        canvas.width = imageWidth;
                        canvas.height = imageHeight;
                        context.drawImage(this,x,y,imageWidth,imageHeight); 

                        /*
                            Orientation:
                            3:ios手机底部在左边,拍出来的横图是倒置的,需要旋转180度
                            6:ios手机底部朝下,拍出来的照片是头在右边,需要逆时针旋转90度
                        */
                        switch(Orientation){
                            case 3:
                                rotateImg(this,'half',canvas);//转两次  
                                break;
                            case 6:
                                rotateImg(this,'left',canvas);  
                                break;
                            case 8:
                                rotateImg(this,'right',canvas);  
                                break;

                            default:
                                break;
                        }
                        // context.rotate(angle);  
                        // 画图
                        // context.drawImage(this,imageHeight); 
                        data = canvas.toDataURL('image/jpeg');  //转成bae64编码
                        callback(data);
                    }); 
                }; 
                reader.readAsDataURL(fileObj);  
            } catch(e) {  
                console.log("压缩失败!");  
                //调用直接上传方式  不压缩 
                directTurnIntoBase64(fileObj,callback); 
            }  
        }
    }  

    //对图片旋转处理 added by lzk  
    function rotateImg(img,direction,canvas) {    
        //alert(img);  
        //最小与最大旋转方向,图片旋转4次后回到原方向    
        var min_step = 0;    
        var max_step = 4;    
        //var img = document.getElementById(pid);    
        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    
        var height = img.height;    
        var width = img.width;    
        //var step = img.getAttribute('step');    
        var 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 if(direction == 'half'){
   
        } else{    
            step--;    
            step < min_step && (step = max_step);    
        }    
        //img.setAttribute('step',step);    
        /*var canvas = document.getElementById('pic_' + pid);   
        if (canvas == null) {   
            img.style.display = 'none';   
            canvas = document.createElement('canvas');   
            canvas.setAttribute('id','pic_' + pid);   
            img.parentNode.appendChild(canvas);   
        }  */  
        //旋转角度以弧度值为参数    
        var degree = step * 90 * Math.PI / 180;    
        var ctx = canvas.getContext('2d');    
        switch (step) {    
            case 0:    
                canvas.width = width;    
                canvas.height = height;    
                ctx.drawImage(img,0);    
                break;    
            case 1:    
                canvas.width = height;    
                canvas.height = width;    
                ctx.rotate(degree);    
                ctx.drawImage(img,-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,0);    
                break;    
        }    
    } 

6、exif.js代码如下:

(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"
    };

     // EXIF 2.3 Spec
    var IFD1Tags = EXIF.IFD1Tags = {
        0x0100: "ImageWidth",0x0101: "ImageHeight",0x0102: "BitsPerSample",0x0103: "Compression",0x0106: "PhotometricInterpretation",0x0111: "StripOffsets",0x0112: "Orientation",0x0115: "SamplesPerPixel",0x0116: "RowsPerStrip",0x0117: "StripByteCounts",0x011A: "XResolution",0x011B: "YResolution",0x011C: "PlanarConfiguration",0x0128: "ResolutionUnit",0x0201: "JpegIFOffset",// When image format is JPEG,this value show offset to JPEG data stored.(aka "ThumbnailOffset" or "JPEGInterchangeFormat")
        0x0202: "JpegIFByteCount",this value shows data size of JPEG image (aka "ThumbnailLength" or "JPEGInterchangeFormatLength")
        0x0211: "YCbCrCoefficients",0x0212: "YCbCrSubSampling",0x0213: "YCbCrPositioning",0x0214: "ReferenceBlackWhite"
    };

    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",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,return light detected",0x0010 : "Flash did not fire,0x0018 : "Flash did not fire,auto mode",0x0019 : "Flash fired,0x001D : "Flash fired,auto mode,0x001F : "Flash fired,0x0020 : "No flash function",0x0041 : "Flash fired,red-eye reduction mode",0x0045 : "Flash fired,red-eye reduction mode,0x0047 : "Flash fired,0x0049 : "Flash fired,0x004D : "Flash fired,0x004F : "Flash fired,0x0059 : "Flash fired,0x005D : "Flash fired,return light not detected,0x005F : "Flash fired,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",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);
            img.exifdata = data || {};
            var iptcdata = findIPTCinJPEG(binFile);
            img.iptcdata = iptcdata || {};
            if (EXIF.isXmpEnabled) {
               var xmpdata= findXMPinJPEG(binFile);
               img.xmpdata = xmpdata || {};               
            }
            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 (self.FileReader && (img instanceof self.Blob || img instanceof self.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,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,bigEnd);
        }
        return tags;
    }


    function readTagValue(file,bigEnd) {
        var type = file.getUint16(entryOffset+2,numValues = file.getUint32(entryOffset+4,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,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,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;
                }
        }
    }

    /**
    * Given an IFD (Image File Directory) start offset
    * returns an offset to next IFD or 0 if it's the last IFD.
    */
    function getNextIFDOffset(dataView,bigEnd){
        //the first 2bytes means the number of directory entries contains in this IFD
        var entries = dataView.getUint16(dirStart,!bigEnd);

        // After last directory entry,there is a 4bytes of data,// it means an offset to next IFD.
        // If its value is '0x00000000',it means this is the last IFD and there is no linked IFD.

        return dataView.getUint32(dirStart + 2 + entries * 12,!bigEnd); // each entry is 12 bytes long
    }

    function readThumbnailImage(dataView,firstIFDOffset,bigEnd){
        // get the IFD1 offset
        var IFD1OffsetPointer = getNextIFDOffset(dataView,tiffStart+firstIFDOffset,bigEnd);

        if (!IFD1OffsetPointer) {
            // console.log('******** IFD1Offset is empty,image thumb not found ********');
            return {};
        }
        else if (IFD1OffsetPointer > dataView.byteLength) { // this should not happen
            // console.log('******** IFD1Offset is outside the bounds of the DataView ********');
            return {};
        }
        // console.log('*******  thumbnail IFD offset (IFD1) is: %s',IFD1OffsetPointer);

        var thumbTags = readTags(dataView,tiffStart + IFD1OffsetPointer,IFD1Tags,bigEnd)

        // EXIF 2.3 specification for JPEG format thumbnail

        // If the value of Compression(0x0103) Tag in IFD1 is '6',thumbnail image format is JPEG.
        // Most of Exif image uses JPEG format for thumbnail. In that case,you can get offset of thumbnail
        // by JpegIFOffset(0x0201) Tag in IFD1,size of thumbnail by JpegIFByteCount(0x0202) Tag.
        // Data format is ordinary JPEG format,starts from 0xFFD8 and ends by 0xFFD9. It seems that
        // JPEG format and 160x120pixels of size are recommended thumbnail format for Exif2.1 or later.

        if (thumbTags['Compression']) {
            // console.log('Thumbnail image found!');

            switch (thumbTags['Compression']) {
                case 6:
                    // console.log('Thumbnail image format is JPEG');
                    if (thumbTags.JpegIFOffset && thumbTags.JpegIFByteCount) {
                    // extract the thumbnail
                        var tOffset = tiffStart + thumbTags.JpegIFOffset;
                        var tLength = thumbTags.JpegIFByteCount;
                        thumbTags['blob'] = new Blob([new Uint8Array(dataView.buffer,tOffset,tLength)],{
                            type: 'image/jpeg'
                        });
                    }
                break;

            case 1:
                console.log("Thumbnail image format is TIFF,which is not implemented.");
                break;
            default:
                console.log("Unknown thumbnail image format '%s'",thumbTags['Compression']);
            }
        }
        else if (thumbTags['PhotometricInterpretation'] == 2) {
            console.log("Thumbnail image format is RGB,which is not implemented.");
        }
        return thumbTags;
    }

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

        var bigEnd,tags,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 + 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 + 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];
            }
        }

        // extract thumbnail
        tags['thumbnail'] = readThumbnailImage(file,bigEnd);

        return tags;
    }

   function findXMPinJPEG(file) {

        if (!('DOMParser' in self)) {
            // console.warn('XML parsing not supported without DOMParser');
            return;
        }
        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,dom = new DOMParser();

        while (offset < (length-4)) {
            if (getStringFromDB(dataView,4) == "http") {
                var startOffset = offset - 1;
                var sectionLength = dataView.getUint16(offset - 2) - 1;
                var xmpString = getStringFromDB(dataView,sectionLength)
                var xmpEndIndex = xmpString.indexOf('xmpMeta>') + 8;
                xmpString = xmpString.substring( xmpString.indexOf( '<x:xmpMeta' ),xmpEndIndex );

                var indexOfXmp = xmpString.indexOf('x:xmpMeta') + 10
                //Many custom written programs embed xmp/xml without any namespace. Following are some of them.
                //Without these namespaces,XML is thought to be invalid by parsers
                xmpString = xmpString.slice(0,indexOfXmp)
                            + 'xmlns:Iptc4xmpCore="http://iptc.org/std/Iptc4xmpCore/1.0/xmlns/" '
                            + 'xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" '
                            + 'xmlns:tiff="http://ns.adobe.com/tiff/1.0/" '
                            + 'xmlns:plus="http://schemas.android.com/apk/lib/com.google.android.gms.plus" '
                            + 'xmlns:ext="http://www.gettyimages.com/xsltExtension/1.0" '
                            + 'xmlns:exif="http://ns.adobe.com/exif/1.0/" '
                            + 'xmlns:stEvt="http://ns.adobe.com/xap/1.0/sType/ResourceEvent#" '
                            + 'xmlns:stRef="http://ns.adobe.com/xap/1.0/sType/ResourceRef#" '
                            + 'xmlns:crs="http://ns.adobe.com/camera-raw-settings/1.0/" '
                            + 'xmlns:xapGImg="http://ns.adobe.com/xap/1.0/g/img/" '
                            + 'xmlns:Iptc4xmpExt="http://iptc.org/std/Iptc4xmpExt/2008-02-29/" '
                            + xmpString.slice(indexOfXmp)

                var domDocument = dom.parseFromString( xmpString,'text/xml' );
                return xml2Object(domDocument);
            } else{
             offset++;
            }
        }
    }

    function xml2json(xml) {
        var json = {};
      
        if (xml.nodeType == 1) { // element node
          if (xml.attributes.length > 0) {
            json['@attributes'] = {};
            for (var j = 0; j < xml.attributes.length; j++) {
              var attribute = xml.attributes.item(j);
              json['@attributes'][attribute.nodeName] = attribute.nodeValue;
            }
          }
        } else if (xml.nodeType == 3) { // text node
          return xml.nodeValue;
        }
      
        // deal with children
        if (xml.hasChildNodes()) {
          for(var i = 0; i < xml.childNodes.length; i++) {
            var child = xml.childNodes.item(i);
            var nodeName = child.nodeName;
            if (json[nodeName] == null) {
              json[nodeName] = xml2json(child);
            } else {
              if (json[nodeName].push == null) {
                var old = json[nodeName];
                json[nodeName] = [];
                json[nodeName].push(old);
              }
              json[nodeName].push(xml2json(child));
            }
          }
        }
        
        return json;
    }

    function xml2Object(xml) {
        try {
            var obj = {};
            if (xml.children.length > 0) {
              for (var i = 0; i < xml.children.length; i++) {
                var item = xml.children.item(i);
                var attributes = item.attributes;
                for(var idx in attributes) {
                    var itemAtt = attributes[idx];
                    var dataKey = itemAtt.nodeName;
                    var dataValue = itemAtt.nodeValue;

                    if(dataKey !== undefined) {
                        obj[dataKey] = dataValue;
                    }
                }
                var nodeName = item.nodeName;

                if (typeof (obj[nodeName]) == "undefined") {
                  obj[nodeName] = xml2json(item);
                } else {
                  if (typeof (obj[nodeName].push) == "undefined") {
                    var old = obj[nodeName];

                    obj[nodeName] = [];
                    obj[nodeName].push(old);
                  }
                  obj[nodeName].push(xml2json(item));
                }
              }
            } else {
              obj = xml.textContent;
            }
            return obj;
          } catch (e) {
              console.log(e.message);
          }
    }

    EXIF.enableXmp = function() {
        EXIF.isXmpEnabled = true;
    }

    EXIF.disableXmp = function() {
        EXIF.isXmpEnabled = false;
    }

    EXIF.getData = function(img,callback) {
        if (((self.Image && img instanceof self.Image)
            || (self.HTMLImageElement && img instanceof self.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.getIptcTag = function(img,tag) {
        if (!imageHasData(img)) return;
        return img.iptcdata[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.getAllIptcTags = function(img) {
        if (!imageHasData(img)) return {};
        var a,data = img.iptcdata,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,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));




转载链接利用exif.js解决ios手机上传竖拍照片旋转90度问题

总结

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