JavaScript如何处理移动端拍摄图片旋转问题

 -1 || ua.indexOf("Adr") > -1;
          // ios终端
          var isIOS = ua.indexOf("iPhone") > -1 || ua.indexOf("iOS") > -1;
          // 修复ios 或 Android
          if (isIOS || isAdr) {
            // 如果方向角不为1，都需要进行旋转
            if (orientation && orientation !== "" && orientation !== 1) {
              switch (orientation) {
                case 6: // 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
                  rotateImg(this, "right90", canvas);
                  break;
                case 3: // 需要180度旋转，转两次
                  rotateImg(this, "right180", canvas);
                  break;
              }
            }
            resultFile = canvas.toDataURL("image/jpeg", fileObj.resolution);
          } else {
            resultFile = canvas.toDataURL("image/jpeg", fileObj.resolution);
          }
          switch (fileObj.fileType) {
            case 1:
            case 2:
              fileObj.callback({
                status: 200,
                message: "success",
                data: dataURLtoFile(resultFile, fileObj.fileType, fileObj.fileName)
              });
              break;
            case 3:
              fileObj.callback({
                status: 200,
                message: "success",
                data: resultFile
              });
              break;
            default:
              break;
          }
        };
      };
      oReader.readAsDataURL(fileObj.file);
    });
  } else {
    return fileObj.callback({
      status: 500,
      message: "文件不存在",
      data: null
    });
  }
  /**
   * 旋转图片
   */
  function rotateImg(img, direction, canvas) {
    if (img === null) return;
    // 最小与最大旋转方向，图片旋转4次后回到原方向
    var minStep = 0;
    var maxStep = 3;
    // img的高度和宽度不能在img元素隐藏后获取，否则会出错
    var width = img.width;
    var height = img.height;
    var step = 2;
    if (step === null) step = minStep;
    if (direction === "right90") {
      step++;
      step > maxStep && (step = minStep);
    } else if(direction === "right180") {
      step = 2;
    } else {
      step--;
      step