ios系统 竖屏拍照 canvas处理后 图片旋转（利用exif.js解决ios手机上传竖拍照片旋转90度问题）

<input type="file" id="files" >
<img src="blank.gif" id="preview">
<script src="exif.js"></script>
<script>
var ipt = document.getElementById(‘files‘),
    img = document.getElementById(‘preview‘),
    Orientation = null;
ipt.onchange = function () {
    var file = ipt.files[0],
        reader = new FileReader(),
        image = new Image();
        
    if(file){
        EXIF.getData(file, function() {  
            Orientation = EXIF.getTag(this, ‘Orientation‘);
        });
        reader.onload = function (ev) {
            image.src = ev.target.result;
            image.onload = function () {
                var imgWidth = this.width,
                    imgHeight = this.height;
                // 控制上传图片的宽高
                if(imgWidth > imgHeight && imgWidth > 750){
                    imgWidth = 750;
                    imgHeight = Math.ceil(750 * this.height / this.width);
                }else if(imgWidth < imgHeight && imgHeight > 1334){
                    imgWidth = Math.ceil(1334 * this.width / this.height);
                    imgHeight = 1334;
                }
                
                var canvas = document.createElement("canvas"),
                ctx = canvas.getContext(‘2d‘);
                canvas.width = imgWidth;
                canvas.height = imgHeight;
                if(Orientation && Orientation != 1){
                    switch(Orientation){
                        case 6:     // 旋转90度
                            canvas.width = imgHeight;    
                            canvas.height = imgWidth;    
                            ctx.rotate(Math.PI / 2);
                            // (0,-imgHeight) 从旋转原理图那里获得的起始点
                            ctx.drawImage(this, 0, -imgHeight, imgWidth, imgHeight);
                            break;
                        case 3:     // 旋转180度
                            ctx.rotate(Math.PI);    
                            ctx.drawImage(this, -imgWidth, -imgHeight, imgWidth, imgHeight);
                            break;
                        case 8:     // 旋转-90度
                            canvas.width = imgHeight;    
                            canvas.height = imgWidth;    
                            ctx.rotate(3 * Math.PI / 2);    
                            ctx.drawImage(this, -imgWidth, 0, imgWidth, imgHeight);
                            break;
                    }
                }else{
                    ctx.drawImage(this, 0, 0, imgWidth, imgHeight);
                }
                img.src = canvas.toDataURL("image/jpeg", 0.8);
            }
        }
        reader.readAsDataURL(file);
    }
}
</script>

<li style="height:100px;line-height:100px"><span  class="">图片</span>
    <canvas id="myCanvas" style="display: none"></canvas>
    <img src=""  id="ago" style="display: none">
    <div class="check_img"><img src=""  id="check_img" ></div>
    <div class="imgupdata">&#xe6a8;
        <!--<input type="file" id="fileId" name="fileId" hidefocus="true">-->
        <input type="file"  id="uploadImage" onchange="selectFileImage(this);" />
    </div>
</li>

function selectFileImage(fileObj) {
    var file = fileObj.files[‘0‘];
    var agoimg=document.getElementById("ago");
    //图片方向角 added by lzk
    var Orientation = null;
    if (file) {
        var rFilter = /^(image\/jpeg|image\/png)$/i; // 检查图片格式
        if (!rFilter.test(file.type)) {
            wfy.alert("请选择jpeg、png格式的图片");
            return;
        }
        // var URL = URL || webkitURL;
        //获取照片方向角属性，用户旋转控制
        EXIF.getData(file, function() {
            EXIF.getAllTags(this);
            Orientation = EXIF.getTag(this, ‘Orientation‘);
        });
        var oReader = new FileReader();
        oReader.onload = function(e) {
            var image = new Image();
            image.src = e.target.result;
            agoimg.src = e.target.result;
            agoimg.onload = function() {
                var expectWidth = this.naturalWidth;
                var expectHeight = this.naturalHeight;
                var calc = expectWidth / expectHeight; //比例参数 实现等比缩放
                var canvas = document.getElementById(‘myCanvas‘);
                var ctx = canvas.getContext("2d");
                canvas.width = 1200;//此处可以随便设置 压缩后的宽度
                canvas.height = (canvas.width)*calc;
                console.log(‘canvas数据‘+canvas.width)
                var base64 = null;
                //修复ios Orientation  ==6 只考虑一种情况 为做全面优化
                if (Orientation == 6) {
                    //alert(‘需要顺时针（向左）90度旋转‘);
                    ctx.save(); //保存状态
                    ctx.translate(canvas.width/2, canvas.height/2); //设置画布上的(0,0)位置，也就是旋转的中心点
                    ctx.rotate(90 * Math.PI / 180); //把画布旋转90度
                    // 执行Canvas的drawImage语句
                    ctx.drawImage(image, -(canvas.width/2), -(canvas.height/2), canvas.width, canvas.height); //把图片绘制在画布translate之前的中心点，这是关键点
                    ctx.restore(); //恢复状态
                }else {
                    ctx.drawImage(image, 0, 0, canvas.width, canvas.height);
                }
                base64 = canvas.toDataURL("image/jpeg", 0.92);
                $("#check_img").attr("src", base64);
            };
        };
        oReader.readAsDataURL(file);
    }
    //$(‘#uploadImage‘).imgloadsize();

}