利用exif.js解决手机上传竖拍照片旋转90180270度问题

原文：https://blog.csdn.net/linlzk/article/details/48652635/

html5+canvas进行移动端手机照片上传时，发现ios手机上传竖拍照片会逆时针旋转90度，横拍照片无此问题；Android手机没这个问题。

因此解决这个问题的思路是：获取到照片拍摄的方向角，对非横拍的ios照片进行角度旋转修正。

利用exif.js读取照片的拍摄信息，详见  http://code.ciaoca.com/javascript/exif-js/

这里主要用到Orientation属性。

Orientation属性说明如下：


旋转角度 参数
0° 1
顺时针90° 6
逆时针90° 8
180° 3


下面就直接上代码了。

主要有html5页面和一个js，示例功能包含了图片压缩和旋转。

自己写的是uploadImage.js。

html5测试页面如下：

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
    <title>图片上传</title>
    <script type="text/javascript" src="js/jquery-1.8.3.js"></script>
    <script type="text/javascript" src="js/uploadPicture/uploadImage.js" ></script>
        <script type="text/javascript" src="js/exif.js" ></script>
    <script>
 
    </script>
</head>
<body>
    <div style="height: 50px; line-height: 50px;text-align: center;border-bottom: 1px solid #171E28;">
            上传图片:
            <input type="file" accept="image/*" id="uploadImage" capture="camera" onchange="selectFileImage(this);" />
        </div>
        <div style="margin-top: 10px;">
            <img alt="preview" src="" id="myImage"/>
        </div>
</body>

</html>

uploadImage.js如下：

function selectFileImage(fileObj) {
    var file = fileObj.files['0'];
    //图片方向角 added by lzk
    var Orientation = null;
    
    if (file) {
        console.log("正在上传,请稍后...");
        var rFilter = /^(image/jpeg|image/png)$/i; // 检查图片格式
        if (!rFilter.test(file.type)) {
            //showMyTips("请选择jpeg、png格式的图片", false);
            return;
        }
        // var URL = URL || webkitURL;
        //获取照片方向角属性，用户旋转控制
        EXIF.getData(file, function() {
           // alert(EXIF.pretty(this));
            EXIF.getAllTags(this); 
            //alert(EXIF.getTag(this, 'Orientation')); 
            Orientation = EXIF.getTag(this, 'Orientation');
            //return;
        });
        
        var oReader = new FileReader();
        oReader.onload = function(e) {
            //var blob = URL.createObjectURL(file);
            //_compress(blob, file, basePath);
            var image = new Image();
            image.src = e.target.result;
            image.onload = function() {
                var expectWidth = this.naturalWidth;
                var expectHeight = this.naturalHeight;
                
                if (this.naturalWidth > this.naturalHeight && this.naturalWidth > 800) {
                    expectWidth = 800;
                    expectHeight = expectWidth * this.naturalHeight / this.naturalWidth;
                } else if (this.naturalHeight > this.naturalWidth && this.naturalHeight > 1200) {
                    expectHeight = 1200;
                    expectWidth = expectHeight * this.naturalWidth / this.naturalHeight;
                }
                var canvas = document.createElement("canvas");
                var ctx = canvas.getContext("2d");
                canvas.width = expectWidth;
                canvas.height = expectHeight;
                ctx.drawImage(this, 0, 0, expectWidth, expectHeight);
                var base64 = null;
                //修复ios
                if (navigator.userAgent.match(/iphone/i)) {
                    console.log('iphone');
                    //alert(expectWidth + ',' + expectHeight);
                    //如果方向角不为1，都需要进行旋转 added by lzk
                    if(Orientation != "" && Orientation != 1){
                        alert('旋转处理');
                        switch(Orientation){
                             case 6://需要顺时针（向左）90度旋转
                                 alert('需要顺时针（向左）90度旋转');
                                 rotateImg(this,'left',canvas);
                                 break;
                             case 8://需要逆时针（向右）90度旋转
                                 alert('需要顺时针（向右）90度旋转');
                                 rotateImg(this,'right',canvas);
                                 break;
                             case 3://需要180度旋转
                                 alert('需要180度旋转');
                                rotateImg(this,'right',canvas);//转两次
                                rotateImg(this,'right',canvas);
                                break;
                        }        
                    }
                    
                    /*var mpImg = new MegaPixImage(image);
                    mpImg.render(canvas, {
                        maxWidth: 800,
                        maxHeight: 1200,
                        quality: 0.8,
                        orientation: 8
                    });*/
                    base64 = canvas.toDataURL("image/jpeg", 0.8);
                }else if (navigator.userAgent.match(/Android/i)) {// 修复android
                    var encoder = new JPEGEncoder();
                    base64 = encoder.encode(ctx.getImageData(0, 0, expectWidth, expectHeight), 80);
                }else{
                    //alert(Orientation);
                    if(Orientation != "" && Orientation != 1){
                        //alert('旋转处理');
                        switch(Orientation){
                             case 6://需要顺时针（向左）90度旋转
                                 alert('需要顺时针（向左）90度旋转');
                                 rotateImg(this,'left',canvas);
                                 break;
                             case 8://需要逆时针（向右）90度旋转
                                 alert('需要顺时针（向右）90度旋转');
                                 rotateImg(this,'right',canvas);
                                 break;
                             case 3://需要180度旋转
                                 alert('需要180度旋转');
                                rotateImg(this,'right',canvas);//转两次
                                rotateImg(this,'right',canvas);
                                break;
                        }        
                    }
                    
                    base64 = canvas.toDataURL("image/jpeg", 0.8);
                }
                //uploadImage(base64);
                $("#myImage").attr("src", base64);
            };
        };
        oReader.readAsDataURL(file);
    }
}
 
//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 = 3;  
        //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 {  
            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, 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;  
        }  
}
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原文地址：https://www.cnblogs.com/shihaiming/p/10755185.html