详解利用exif.js解决ios手机上传竖拍照片旋转90度问题

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，这里主要用到Orientation属性。

Orientation属性说明如下：

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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