圖像旋轉但縮略圖不是

Question

我想旋轉基於EXIF標記的圖像。我能夠成功處理圖像的旋轉，但在Windows資源管理器中的縮略圖仍然是顛倒的。打開圖像時絕對沒問題。已驗證修正的方向here.以下代碼的問題是，EXIF數據似乎沒有任何有關縮略圖方向的信息。我要的是：

1. 如果沒有可用的縮略圖方向，旋轉縮略圖和縮略圖定位更新圖像的元數據。

2. 如果沒有可用的縮略圖方向信息，請旋轉縮略圖並添加縮略圖方向的圖像元數據。

我使用的代碼是：

public static RotateFlipType RotateImageByExifOrientationData(Image img, string oldFileName, string sourceFilePath, out string newFileName) 
{  
    int orientationId = 0x0112;//Image orientation 
    int thumbnailOrientationId = 0x5029;//Thumbnail orientation 
    var fType = RotateFlipType.RotateNoneFlipNone; 

    if (img.PropertyIdList.Contains(orientationId)) 
    { 
     var pItem = img.GetPropertyItem(orientationId); 
     //Get the orientation 
     fType = GetRotateFlipTypeByExifOrientationData(pItem.Value[0]); 
     if (fType != RotateFlipType.RotateNoneFlipNone) 
     { 
      img.RotateFlip(fType); 

      // Read orientation tag. Update to normal so that the other clients(image viewer or browser) will not rotate the rotated image.          
      // Force value to 1 
      pItem.Value = BitConverter.GetBytes((short)1); 
      img.SetPropertyItem(pItem); 
      PropertyItem thumbnailItem; 
      if (img.PropertyIdList.Contains(thumbnailOrientationId)) 
      { 
       //If thumbnail metadata is available, update it. 
       thumbnailItem = img.GetPropertyItem(thumbnailOrientationId); 
       thumbnailItem.Value = BitConverter.GetBytes((short)1); 
       img.SetPropertyItem(thumbnailItem); 
      } 
      else 
      { 
       //If thumbnail metadata is not available, add appropriate metadata. 
       thumbnailItem = img.PropertyItems[0]; 
       thumbnailItem.Id = thumbnailOrientationId; 
       thumbnailItem.Type = 2; 
       thumbnailItem.Value = BitConverter.GetBytes((short)1); 
       thumbnailItem.Len = thumbnailItem.Value.Length; 
       img.SetPropertyItem(thumbnailItem); 
      } 
      newFileName = "Rotated_" + oldFileName; 
      string targetFilePath = sourceFilePath + newFileName ; 
      ImageFormat targetFormat = ImageFormat.Jpeg; 
      img.Save(targetFilePath, targetFormat); 
      File.Delete(sourceFilePath + oldFileName);//Delete old file. 
     } 
    } 
    return fType; 
} 

Answer 1

是一個老問題，但經過一番研究，我發現，即使去除圖像（0x0112）的方向和的方向後，縮略圖（0x5029），當再次嘗試生成縮略圖時，仍保留相同的方向。所以我檢查了一些JPG的縮略圖以字節「嵌入」。所以刪除字節（0x501B）後，我能夠正確生成縮略圖。

簡單的代碼所示：

var rotateImage = Image.FromStream(fileStream); 
    switch (degree) 
    { 
     case eRotateImagem.Degree_90: 
      rotateImage.RotateFlip(RotateFlipType.Rotate90FlipNone); 
      break; 
     case eRotateImagem.Degree_180: 
      rotateImage.RotateFlip(RotateFlipType.Rotate180FlipNone); 
      break; 
     case eRotateImagem.Degree_270: 
      rotateImage.RotateFlip(RotateFlipType.Rotate270FlipNone); 
      break; 
    } 

    int orientationId = 0x0112; //Image orientation 
    int thumbnailOrientationId = 0x5029; //Thumbnail orientation 
    int thumbnailBytes = 0x501B; //Thumbnail bytes 

    if (rotateImage.PropertyIdList.Contains(orientationId)) 
    { 
     rotateImage.RemovePropertyItem(orientationId); 
    } 
    if (rotateImage.PropertyIdList.Contains(thumbnailOrientationId)) 
    { 
     rotateImage.RemovePropertyItem(thumbnailOrientationId); 
    } 
    if (rotateImage.PropertyIdList.Contains(thumbnailBytes)) 
    { 
     rotateImage.RemovePropertyItem(thumbnailBytes); 
    }