前言

近期有个手机端html5上传图片功能的项目，在android手机上体验很好但在IOS手机上，图片有时会出现角度旋转。google后找到了解决方法，现在总结下供以后使用。

html页面

<div class="uploadImage"><input type="file"></div>
<img id="myImage">
<script src="https://apps.bdimg.com/libs/jquery/2.1.4/jquery.min.js"></script>
<script type="text/javascript" src="js/exif.js"></script>
<script type="text/javascript" src="js/uploadImage.js"></script>

exif.js是获取图片角度的javascript插件

uploadImage.js

$(".uploadImage input").change(function () {
    selectFileImage($(this)[0]);
});

function selectFileImage(fileObj) {
    var file = fileObj.files[0];
    // 图片方向角
    var Orientation = null;

    if (file) {
        var rFilter = /^(image\/jpeg|image\/png)$/i; // 检查图片格式

        if (!rFilter.test(file.type)) {
            alert("请选择jpeg、png格式的图片");
            return;
        }
        //获取照片方向角属性
        EXIF.getData(file, function () {
            EXIF.getAllTags(this);
            Orientation = EXIF.getTag(this, 'Orientation');
        });
    }
    var reader = new FileReader();
    reader.readAsDataURL(file);
    reader.onload = function (e) {
        var image = new Image();
        image.src = e.target.result;
        image.onload = function () {
            var canvas = document.createElement("canvas");
            canvas.width = this.naturalWidth;
            canvas.height = this.naturalHeight;
            var ctx = canvas.getContext("2d");
            ctx.drawImage(this, 0, 0, this.naturalWidth, this.naturalHeight);
            var base64 = null;
            if (Orientation != "" && Orientation != 1 && Orientation != undefined) {
                var width = this.naturalWidth;
                var height = this.naturalHeight;
                switch (Orientation) {
                    case 6://需要顺时针90度旋转
                        canvas.width = height;
                        canvas.height = width;
                        ctx.rotate(90 * Math.PI / 180);
                        ctx.drawImage(this, 0, -height);
                        break;
                    case 8://需要逆时针90度旋转
                        canvas.width = height;
                        canvas.height = width;
                        ctx.rotate(-90 * Math.PI / 180);
                        ctx.drawImage(this, -width, 0);
                        break;
                    case 3://需要180度旋转
                        ctx.rotate(180 * Math.PI / 180);
                        ctx.drawImage(this, -width, -height);
                        break;
                }
            }
            base64 = canvas.toDataURL("image/png");
            $("#myImage").attr("src", base64);
        };
    };
}