我正在尝试修改/写入合理的属性项。一个合理的 Exif 属性是 Exposure Time：
来自 EXIF 标签的信息：0x829a、ExposureTime、rational64u、ExifIFD
然而，我遇到了障碍，不知道如何继续。我设法从图像中读取了曝光时间。不幸的是，我在理解如何更改和设置值时遇到了一些问题。
读取曝光时间的代码：
Public Class Class1
Private Image As Bitmap ' I have code to get the filepath of the image, which I didn't include here.
Public Function RationalRead()
Dim item = Image.GetPropertyItem(&H829A)
Dim Num = BitConverter.ToUInt32(item.Value, 0)
Dim Denom = BitConverter.ToUInt32(item.Value, 4)
Dim expostime = Num & "/" & Denom
Return expostime
End Function
End Class
到目前为止我编写曝光时间的代码：
Public Class Class1
Private Image As Bitmap ' I have code to get the filepath of the image, which I didn't include here.
Public Sub RationalWrite()
Dim item = Image.PropertyItems(&H829A)
Dim Num = BitConverter.ToUInt32(item.Value, 0) ' I would need to be able to change the value inside the first bit here to something different.
Dim Denom = BitConverter.ToUInt32(item.Value, 4) ' I would need to be able to change the value inside the fourth bit here to something different.
Dim ImageProperty As Imaging.PropertyItem = Image.PropertyItems(0)
ImageProperty.Id = &HA404 ' The Metatag ID to modify (in our case ExposureTime)
ImageProperty.Value = ' Here I would need to combine Num and Denom so that ImageProperty.Value can read the bits.
ImageProperty.Type = 5 ' The 5 stands for UnsignedRational
ImageProperty.Len = 8 ' I don't know if this should be 7 or 8.
Image.SetPropertyItem(ImageProperty)
End Sub
End Class
对我的“混乱”的任何帮助将不胜感激！