C#编辑图像文件EXIF信息

private void setImageTag(string imgFile, string tagFile, string imgTag, string imgTitle)
{
    uint padding = 2048;
    if (File.Exists(imgFile))
    {
        BitmapDecoder decoder = null;
        // load the jpg file with a JpegBitmapDecoder  
        using (Stream jpegStreamIn = File.Open(imgFile, FileMode.Open, FileAccess.ReadWrite, FileShare.None))
        {
            decoder = new JpegBitmapDecoder(jpegStreamIn, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.OnLoad);
        }
        if (decoder != null)
        {
            BitmapFrame bitmapFrame = decoder.Frames[0];
            if (bitmapFrame != null)
            {
                // the size of the metadata has been increased and we can't save it  
                BitmapMetadata metaData = (BitmapMetadata)bitmapFrame.Metadata.Clone();
                if (metaData != null)
                {
                    // Add padding  
                    metaData.SetQuery("/app1/ifd/PaddingSchema:Padding", padding);
                    metaData.Title = imgTitle;
                    List<string> taglist = new List<string>();
                    taglist.Add(imgTag);
                    metaData.Keywords = new System.Collections.ObjectModel.ReadOnlyCollection<string>(taglist);
                    // get an encoder to create a new jpg file with the addit'l metadata.  
                    JpegBitmapEncoder encoder = new JpegBitmapEncoder();
                    encoder.Frames.Add(BitmapFrame.Create(bitmapFrame, bitmapFrame.Thumbnail, metaData, bitmapFrame.ColorContexts));
                    using (Stream jpegStreamOut = File.Open(tagFile, FileMode.CreateNew, FileAccess.ReadWrite))
                    {
                        encoder.Save(jpegStreamOut);
                    }
                }
            }
        }
    }
}

其中22行，添加PADDING是不能少的，否则编辑信息保存不上。