JS解决IOS中拍照图片预览旋转90度BUG的问题

//获取图片方向
function getPhotoOrientation(img) {
   var orient;
   EXIF.getData(img, function () {
      orient = EXIF.getTag(this, 'Orientation');
   });
   return orient;
}

//图片压缩
function compress(img, width, height, ratio) {
   var canvas, ctx, img64, orient;
　　　 
   //获取图片方向
   orient = getPhotoOrientation(img);

   canvas = document.createElement('canvas');
   canvas.width = width;
   canvas.height = height;

   ctx = canvas.getContext("2d");

   //如果图片方向等于6 ，则旋转矫正，反之则不做处理
   if (orient == 6) {
      ctx.save();
      ctx.translate(width / 2, height / 2);
      ctx.rotate(90 * Math.PI / 180);
      ctx.drawImage(img, 0 - height / 2, 0 - width / 2, height, width);
      ctx.restore();
   } else {
      ctx.drawImage(img, 0, 0, width, height);
   }

   img64 = canvas.toDataURL("image/jpeg", ratio);
   return img64;
}