.Net缩略图在从移动设备创建时旋转图像

Question

我正在使用以下答案中的代码来设置上传图像的缩略图.

/sf/answers/140102371/

这完美地工作并填充图像,保持纵横比等但如果我从我的手机上传图像,从这种方法保存的缩略图图像旋转ccw 90度.

你知道是什么原因造成的吗？使用AjaxFileUpload1.SaveAs(MapPath("〜/ catalog/images /"&imageFilename))(来自AJAX控件工具包)保存原始图像,并以正确的方向显示.

谢谢

Answer 1

也许这是由于图像被物理地存储在它所显示的不同方向上,例如,用相机侧向拍摄的640*480可以存储为480*640,具有方向exif数据标记.

这很棒,因为explorer/paint/photoshop /几乎每个观众都会看到exif标志并在呈现之前旋转它.但是,.net Image类不要(当你知道发生了什么时这似乎是合理的),所以你必须要设置exif rotate attrib在新的缩略图上(我不喜欢,因为我不喜欢)在缩略图上有任何属性)或自己检查和旋转缩略图.

下面是一个粗略的方法来做到这一点.请注意,我已将c#中的代码作为您引用的答案的修改版本提供,因为它也是c#.转换到vb.net应该很直接:)

  if (sourceImage.PropertyIdList.Contains(0x112)) //0x112 = Orientation
  {
     var prop = sourceImage.GetPropertyItem(0x112);
     if (prop.Type == 3 && prop.Len == 2)
     {
        UInt16 orientationExif = BitConverter.ToUInt16(sourceImage.GetPropertyItem(0x112).Value, 0);
        if (orientationExif == 8)
        {
           newImage.RotateFlip(RotateFlipType.Rotate270FlipNone);
        }
        else if (orientationExif == 3)
        {
           newImage.RotateFlip(RotateFlipType.Rotate180FlipNone);
        }
        else if (orientationExif == 6)
        {
           newImage.RotateFlip(RotateFlipType.Rotate90FlipNone);
        }
     }
  }

因此更新的FixedSize代码将是这样的:

static Image FixedSize(Image imgPhoto, int Width, int Height)
{
    int sourceWidth = imgPhoto.Width;
    int sourceHeight = imgPhoto.Height;
    int sourceX = 0;
    int sourceY = 0;
    int destX = 0;
    int destY = 0;

    float nPercent = 0;
    float nPercentW = 0;
    float nPercentH = 0;

    nPercentW = ((float)Width / (float)sourceWidth);
    nPercentH = ((float)Height / (float)sourceHeight);
    if (nPercentH < nPercentW)
    {
        nPercent = nPercentH;
        destX = System.Convert.ToInt16((Width -
                      (sourceWidth * nPercent)) / 2);
    }
    else
    {
        nPercent = nPercentW;
        destY = System.Convert.ToInt16((Height -
                      (sourceHeight * nPercent)) / 2);
    }

    int destWidth = (int)(sourceWidth * nPercent);
    int destHeight = (int)(sourceHeight * nPercent);

    Bitmap bmPhoto = new Bitmap(Width, Height,
                      PixelFormat.Format24bppRgb);
    bmPhoto.SetResolution(imgPhoto.HorizontalResolution,
                     imgPhoto.VerticalResolution);

    Graphics grPhoto = Graphics.FromImage(bmPhoto);
    grPhoto.Clear(Color.Red);
    grPhoto.InterpolationMode =
            InterpolationMode.HighQualityBicubic;

    grPhoto.DrawImage(imgPhoto,
        new Rectangle(destX, destY, destWidth, destHeight),
        new Rectangle(sourceX, sourceY, sourceWidth, sourceHeight),
        GraphicsUnit.Pixel);

    grPhoto.Dispose();

    //Rotate image to what is expected.
    if (imgPhoto.PropertyIdList.Contains(0x112)) //0x112 = Orientation
    {
       var prop = imgPhoto.GetPropertyItem(0x112);
       if (prop.Type == 3 && prop.Len == 2)
       {
          UInt16 orientationExif = BitConverter.ToUInt16(sourceImage.GetPropertyItem(0x112).Value, 0);
          if (orientationExif == 8)
          {
             bmPhoto.RotateFlip(RotateFlipType.Rotate270FlipNone);
          }
          else if (orientationExif == 3)
          {
             bmPhoto.RotateFlip(RotateFlipType.Rotate180FlipNone);
          }
          else if (orientationExif == 6)
          {
             bmPhoto.RotateFlip(RotateFlipType.Rotate90FlipNone);
          }
       }
    }

    return bmPhoto;
}

请注意,这并不包括每个exif方向,只是常见的方向.

参考文献:

http://www.impulseadventure.com/photo/exif-orientation.html

http://msdn.microsoft.com/en-us/library/xddt0dz7.aspx

ps:这是我的第一个堆栈溢出答案,所以请轻松反馈;)