ASP中显示数据库图象字段的问题?
我将JPG图象文件以OLE对象字段的形式（非链接）存入ACCESS97数据库中,然后编写下面的代码,为何却不能在浏览器中正常显示该JPG文件？
<%@ Language=VBScript %>
<%
Private Sub Disp_photo()
Dim P
Dim L
L=1024 '以1K为单位向Client端写数据
Response.ContentType="Image/JPEG"
do
P=rs("picture").Getchunk(L)
Response.BinaryWrite P
if (LenB(P)< L) then exit do
loop
End Sub
%>
<OBJECT RUNAT=server PROGID=ADODB.Connection id=Conn> </OBJECT>
<OBJECT RUNAT=server PROGID=ADODB.Recordset id=rs> </OBJECT>
<%
Response.Buffer=true
strSQL="select product, picture from Product"
Conn.Open "yuegang"
rs.Open "Product",Conn
if not (rs.eof and rs.bof) then
Disp_photo
End if
%>
问题点数：120、回复次数：1Top
1 楼edyang（化石）回复于 2000-11-22 18:28:00 得分 120
你需要把 OLE 对象的 OLE 头部信息去掉才可以。下面是 MSDN 上的一篇文章，可以解决你的问题：
HOWTO: Retrieving Bitmap from Access and Displaying In Web Page
ID: Q175261
--------------------------------------------------------------------------------
The information in this article applies to:
Active Server Pages
Microsoft Visual Basic Professional and Enterprise Editions for Windows, versions 5.0, 6.0
--------------------------------------------------------------------------------
SUMMARY
This article shows by example how to extract the bitmap photos in the Microsoft Access 97 Northwind.mdb database, and view them from a Web browser using Active Server Pages (ASP). In order to accomplish this task, an ActiveX DLL must be created that strips the Access and OLE headers from the field. This article shows how to create this ActiveX DLL, and how to implement it.
MORE INFORMATION
WARNING: ANY USE BY YOU OF THE CODE PROVIDED IN THIS ARTICLE IS AT YOUR OWN RISK. Microsoft provides this code "as is" without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and/or fitness for a particular purpose.
This article demonstrates how to use Visual Basic to retrieve a bitmap stored in an OLE Object field. Because the definition of OLE object storage is not documented, the following code searches the object's OLE header for characters consistent with the start of the graphic. This method may not work in all circumstances.
Be aware that Internet Explorer 3.0 is unable to display true color bitmaps. For this reason, the bitmaps stored in the Access database should be no higher than 256 colors.
Step-by-Step Example to Extract the Photos
Create a new project in Visual Basic and make the project an ActiveX DLL.
Add a reference to ActiveX Data Objects (ADO) by clicking the Project menu and selecting References. Select "Microsoft OLE DB ActiveX Data Objects 1.0 Library" and click OK.
Add a new module to the project by selecting the Project menu and clicking Add Module. Select Module and click Open.
Place the following code in the (general) (declarations) section of MODULE1.BAS:
' Enter the following Declare statement as one single line:
Public Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory"
(lpvDest As Any, lpvSource As Any, ByVal cbCopy As Long)
Type PT
Width As Integer
Height As Integer
End Type
Type OBJECTHEADER
Signature As Integer
HeaderSize As Integer
ObjectType As Long
NameLen As Integer
ClassLen As Integer
NameOffset As Integer
ClassOFfset As Integer
ObjectSize As PT
OleInfo As String * 256
End Type
Place the following code in the (general) (declarations) section of CLASS1.CLS:
Function DisplayBitmap(ByVal OleField As Variant)
Dim Arr() As Byte
Dim ObjHeader As OBJECTHEADER
Dim Buffer As String
Dim ObjectOffset As Long
Dim BitmapOffset As Long
Dim BitmapHeaderOffset As Integer
Dim ArrBmp() As Byte
Dim i As Long
'Resize the array, then fill it with
'the entire contents of the field
ReDim Arr(OleField.ActualSize)
Arr() = OleField.GetChunk(OleField.ActualSize)
'Copy the first 19 bytes into a variable
'of the OBJECTHEADER user defined type.
CopyMemory ObjHeader, Arr(0), 19
'Determine where the Access Header ends.
ObjectOffset = ObjHeader.HeaderSize + 1
'Grab enough bytes after the OLE header to get the bitmap header.
Buffer = ""
For i = ObjectOffset To ObjectOffset + 512
Buffer = Buffer & Chr(Arr(i))
Next i
'Make sure the class of the object is a Paint Brush object
If Mid(Buffer, 12, 6) = "PBrush" Then
BitmapHeaderOffset = InStr(Buffer, "BM")
If BitmapHeaderOffset > 0 Then
'Calculate the beginning of the bitmap
BitmapOffset = ObjectOffset + BitmapHeaderOffset - 1
'Move the bitmap into its own array
ReDim ArrBmp(UBound(Arr) - BitmapOffset)
CopyMemory ArrBmp(0), Arr(BitmapOffset), UBound(Arr) -
BitmapOffset + 1
'Return the bitmap
DisplayBitmap = ArrBmp
End If
End If
End Function
Rename the Project by selecting the Project menu, and clicking on "Project1 Properties" and type your new name in the "Project Name" field. This example assumes that you named the project "MyProject" and will refer to that name in future steps.
Make the project Apartment Model Threaded by selecting the "Unattended Execution" check box. Click OK.
Rename the Class in the Property Pane. This example assumes that you named the class "MyClass" and refers to that name in future steps.
Compile the DLL by clicking the File menu and selecting "Make MyProject.dll."
Create an ASP page named "bitmap.asp" that contains the following code:
<%@ LANGUAGE="VBSCRIPT" %>
<%
' You need to set up a System DSN named 'NWind' that points to
' the Northwind.mdb database
Set DataConn = Server.CreateObject("ADODB.Connection")
DataConn.Open "DSN=NWind", "admin", ""
Set cmdTemp = Server.CreateObject("ADODB.Command")
Set RS = Server.CreateObject("ADODB.Recordset")
cmdTemp.CommandText = "SELECT Photo FROM Employees
WHERE EmployeeID = 1"
cmdTemp.CommandType = 1
Set cmdTemp.ActiveConnection = DataConn
RS.Open cmdTemp, , 0, 1
Response.ContentType = "image/bmp"
Set Bitmap = Server.CreateObject("MyProject.MyClass")
Response.BinaryWrite Bitmap.DisplayBitmap(RS("Photo"))
RS.Close
%>
Create an HTML page named "BitmapTest.htm" that contains the following code:
<HTML>
<HEAD>
<TITLE>Bitmap Test</TITLE>
</HEAD>
<BODY>
<HR>
<img src="Bitmap.asp">
<HR>
</BODY>
</HTML>
REFERENCES
For additional information, please see the following article in the Microsoft Knowledge Base:
Q173308 HOWTO: Displaying Images Stored in a BLOB Field
For the latest Knowledge Base artices and other support information on Visual InterDev and Active Server Pages, see the following page on the Microsoft Technical Support site:
http://support.microsoft.com/support/vinterdev/
Additional query words:
Keywords : kbsample kbAccess kbADO kbASP kbCOMt kbVBp kbGrpASP kbiis500
Version : WINDOWS:5.0,6.0; winnt:
Platform : WINDOWS winnt
Issue type : kbhowto
Last Reviewed: October 12, 1999
© 1999 Microsoft Corporation. All rights reserved. Terms of Use.
--------------------------------------------------------------------------------
Send feedback to MSDN.Look here for MSDN Online resources. Top
