将Access数据库中存储的图片加载到程序VB.NET中 [英] Loading Picture Stored in Access Database into Program VB.NET

问题描述

我有一个通过数据源与VB项目链接的Access数据库。在其中一个表的数据库中，我有一个OLE对象字段。我已在此字段中以.BMP格式和.JPG格式保存图片。我遇到的问题是将此图像加载到我的应用程序中。这是我希望能够做到的：

 ButtonMeal1.BackgroundImage = IPOSDBDataSet.Meals.Rows（ 0 ）。项目（ 5 ）

其中Item（5）是存储图像的行的列。但是，我知道这不起作用。



我也试过这种方法：



< pre lang =vb> Dim ImageByteArray As 字节（）= CType （IPOSDBDataSet.Meals.Rows（ 0 ）。Item（ 5 ），字节（））
Dim ImageMemoryStream As MemoryStream = 新 IO.MemoryStream（ImageByteArray）
Dim MyImage As Image = Drawing.Image.FromStream（ImageMemoryStream）
PictureBox1.Image = MyImage

但是，当我调试这个时，我收到错误参数无效。我已经多次修改了这个，但是没有任何好的结果。



我还读过关于存储在OLE Object字段中的标题的东西，它必须是删除了，但我不知道怎么做！关于我的问题，互联网上没有明确的答案。最终，我希望能够以任何可能的方式从数据库中将图像加载到我的程序中！



请帮忙！

解决方案

使用Northwind.sdf文件时我碰到了OLE图像格式。奇怪的是，DataGridView Image列可以处理这些数据，但Image Class不能。



我修改了本文中的代码（ http://blogs.msdn.com/b/pranab/archive/2008/07/15/removing-ole-header-from-images-stored-in-ms-access-db-as-ole-object.aspx [ ^ ]）从函数中删除字节数组中的OLE数据。



修改代码的这一行以使用该函数。

 Dim ImageMemoryStream作为MemoryStream = New IO。 MemoryStream（GetImageBytesFromOLEField（ImageByteArray））

 朋友 共享 函数 GetImageBytesFromOLEField（ ByVal  oleFieldBytes（） As  字节）作为 字节（）
 
  Dim  BITMAP_ID_BLOCK 作为 字符串 =   BM 
  Dim  JPG_ID_BLOCK  As   String  = ChrW（& HFF）.ToString（）& ChrW（& HD8）.ToString（）& ChrW（& HFF）.ToString（）
  Dim  PNG_ID_BLOCK  As   String  = ChrW（& H89）.ToString（）&   PNG& vbCrLf& ChrW（& H1A）.ToString（）& vbLf 
  Dim  GIF_ID_BLOCK  As   String  =   GIF8 
  Dim  TIFF_ID_BLOCK 作为 字符串 =  < span class =code-string> II *& ChrW（& H0）.ToString（）
 
  Dim  imageBytes（） As  字节 
 
 ' 获取UTF7编码字符串版本 
  Dim  u7  As  System.Text.Encoding = System.Text.Encoding.UTF7 
  Dim  strTemp  As   String  = u7.GetString（oleFieldBytes）
  Dim  st2  As  < span class =code-keyword> String  = System.Text.Encoding.UTF8.GetString（oleFieldBytes）
 ' 从字符串中获取前300个字符 
  Dim  strVTemp  As   String  = strTemp.Substring（ 0 ， 300 ）
 
 ' 搜索块 
  Dim  iPos 作为 整数 = -1 
 如果 strVTemp.IndexOf（BITMAP_ID_BLOCK）<> -1 然后 
 iPos = strVTemp.IndexOf（BITMAP_ID_BLOCK）
  ElseIf  strVTemp。 IndexOf（JPG_ID_BLOCK）<> -1 然后 
 iPos = strVTemp.IndexOf（JPG_ID_BLOCK）
  ElseIf  strVTemp。 IndexOf（PNG_ID_BLOCK）<> -1 然后 
 iPos = strVTemp.IndexOf（PNG_ID_BLOCK）
  ElseIf  strVTemp。 IndexOf（GIF_ID_BLOCK）<> -1 然后 
 iPos = strVTemp.IndexOf（GIF_ID_BLOCK）
  ElseIf  strVTemp。 IndexOf（TIFF_ID_BLOCK）<> -1 然后 
 iPos = strVTemp.IndexOf（TIFF_ID_BLOCK）
 否则 
 抛出 新异常（ < span class =code-string>无法确定OLE对象的标题大小）
 结束 如果 
 
 
 ' 从上面的位置获取新图片 
 如果 iPos = -1 那么 
 < span class =code-keyword>抛出 新异常（ 无法确定OLE对象的标题大小）
 结束 如果 
 
 imageBytes = 新 字节（ CInt （oleFieldBytes.LongLength  -  iPos -   1 ））{} 
 Array.ConstrainedCopy（oleFieldBytes，iPos，imageBytes， 0 ， oleFieldBytes.Length  -  iPos）
 
 返回 imageBytes 
 
 结束 功能 

I have an Access Database linked with a VB project through a data source. In the database on one of the tables, I have an OLE Object field. I have saved pictures in .BMP format and .JPG format in this field. The problem I am encountering is loading this image into my application. This is what I would like to be able to do:

ButtonMeal1.BackgroundImage = IPOSDBDataSet.Meals.Rows(0).Item(5)

Where Item(5) is the column of the row where the image is stored. However, I know that this does not work.

I have also tried this method:

Dim ImageByteArray As Byte() = CType(IPOSDBDataSet.Meals.Rows(0).Item(5), Byte())
Dim ImageMemoryStream As MemoryStream = New IO.MemoryStream(ImageByteArray)
Dim MyImage As Image = Drawing.Image.FromStream(ImageMemoryStream)
PictureBox1.Image = MyImage

However, when I debug this, I get the error "Parameter is not valid". I have modified this multiple times, but without any good result.

I have also read stuff about a header being stored in the OLE Object field, and that it must be removed, but I have no idea how to do this! There are no clear answers on the internet regarding my issue. Ultimately, I would just like to be able to load an image into my program from a database, whatever way possible!

Please help!

解决方案

I bumped into the OLE image format when using the Northwind.sdf file. The strange thing is that the DataGridView Image column can handle this data, but the Image Class can not.

I modified the code from this article (http://blogs.msdn.com/b/pranab/archive/2008/07/15/removing-ole-header-from-images-stored-in-ms-access-db-as-ole-object.aspx[^]) into a function to strip out the OLE data from a byte array.

Modify this line of your code to use the function.

Dim ImageMemoryStream As MemoryStream = New IO.MemoryStream(GetImageBytesFromOLEField(ImageByteArray))

Friend Shared Function GetImageBytesFromOLEField(ByVal oleFieldBytes() As Byte) As Byte()

   Dim BITMAP_ID_BLOCK As String = "BM"
   Dim JPG_ID_BLOCK As String = ChrW(&HFF).ToString() & ChrW(&HD8).ToString() & ChrW(&HFF).ToString()
   Dim PNG_ID_BLOCK As String = ChrW(&H89).ToString() & "PNG" & vbCrLf & ChrW(&H1A).ToString() & vbLf
   Dim GIF_ID_BLOCK As String = "GIF8"
   Dim TIFF_ID_BLOCK As String = "II*" & ChrW(&H0).ToString()

   Dim imageBytes() As Byte

   ' Get a UTF7 Encoded string version
   Dim u7 As System.Text.Encoding = System.Text.Encoding.UTF7
   Dim strTemp As String = u7.GetString(oleFieldBytes)
   Dim st2 As String = System.Text.Encoding.UTF8.GetString(oleFieldBytes)
   ' Get the first 300 characters from the string
   Dim strVTemp As String = strTemp.Substring(0, 300)

   ' Search for the block
   Dim iPos As Integer = -1
   If strVTemp.IndexOf(BITMAP_ID_BLOCK) <> -1 Then
      iPos = strVTemp.IndexOf(BITMAP_ID_BLOCK)
   ElseIf strVTemp.IndexOf(JPG_ID_BLOCK) <> -1 Then
      iPos = strVTemp.IndexOf(JPG_ID_BLOCK)
   ElseIf strVTemp.IndexOf(PNG_ID_BLOCK) <> -1 Then
      iPos = strVTemp.IndexOf(PNG_ID_BLOCK)
   ElseIf strVTemp.IndexOf(GIF_ID_BLOCK) <> -1 Then
      iPos = strVTemp.IndexOf(GIF_ID_BLOCK)
   ElseIf strVTemp.IndexOf(TIFF_ID_BLOCK) <> -1 Then
      iPos = strVTemp.IndexOf(TIFF_ID_BLOCK)
   Else
      Throw New Exception("Unable to determine header size for the OLE Object")
   End If


   ' From the position above get the new image
   If iPos = -1 Then
   Throw New Exception("Unable to determine header size for the OLE Object")
   End If

   imageBytes = New Byte(CInt(oleFieldBytes.LongLength - iPos - 1)) {}
   Array.ConstrainedCopy(oleFieldBytes, iPos, imageBytes, 0, oleFieldBytes.Length - iPos)

   Return imageBytes

End Function

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