|
-
Sep 30th, 2010, 07:12 AM
#1
Thread Starter
New Member
storing images in database in binary format
Hello
I am using this code showed below but I do not know why the images stored in binary form are increasing the size of the database too much. For example, a 800KB jpg image which is added that way to the Access database increase the mdb file in 1600KB. Considering that this way should not bloat the database according to http://jamiessoftware.tk/articles/handlingimages.html, I still do not understand why this is happening.
Anyways,would you recommend to store 10GB of image files in a database following the code below (third opion in http://jamiessoftware.tk/articles/ha...e file system?
I mean, even if I got that this code did not increase the database size more than the image file's size for each image added, at some point the database might reach 10GB or even more depending on the amount of pictures I have. Is that a good idea? By the way, what is the biggest file size allowed for an mdb file in Access 97, 2000, 2003, 2007 and 2010? If this size is just a few gigabytes, Isn't there a much more powerful and freeware database manager whose databases could grow up at least up to 100GB and somehow integrated/linked to show up in Access interface as if they really were access databases in case access was not powerful enough in order to store huge amount of data like the image files I told you about?
Otherwise, would this mean that for the time being my only options are either to store only the file paths of the images instead of the images themselves in the access database for a freeware solution or buying sql server in case I do not mind paying to build a huge database with many image files growing like 100GB?
Code:
Option Compare Database
Option Explicit
Const BlockSize = 32768
'**************************************************************
' FUNCTION: ReadBLOB()
'
' PURPOSE:
' Reads a BLOB from a disk file and stores the contents in the
' specified table and field.
'
' PREREQUISITES:
' The specified table with the OLE object field to contain the
' binary data must be opened in Visual Basic code and the correct
' record navigated to prior to calling the ReadBLOB() function.
'
' ARGUMENTS:
' Source - The path and filename of the binary information
' to be read and stored.
' T - The table object to store the data in.
' Field - The OLE object field in table T to store the data in.
'
' RETURN:
' The number of bytes read from the Source file.
'**************************************************************
Function ReadBLOB(Source As String, T As DAO.Recordset, _
sField As String)
Dim NumBlocks As Integer, SourceFile As Integer, i As Integer
Dim FileLength As Long, LeftOver As Long
Dim FileData As String
Dim RetVal As Variant
On Error GoTo Err_ReadBLOB
' Open the source file.
SourceFile = FreeFile
Open Source For Binary Access Read As SourceFile
' Get the length of the file.
FileLength = LOF(SourceFile)
If FileLength = 0 Then
ReadBLOB = 0
Exit Function
End If
' Calculate the number of blocks to read and leftover bytes.
NumBlocks = FileLength \ BlockSize
LeftOver = FileLength Mod BlockSize
' SysCmd is used to manipulate status bar meter.
RetVal = SysCmd(acSysCmdInitMeter, "Reading BLOB", _
FileLength \ 1000)
' Put first record in edit mode.
T.MoveLast
T.Edit
' Read the leftover data, writing it to the table.
FileData = String$(LeftOver, 32)
Get SourceFile, , FileData
T(sField).AppendChunk (FileData)
RetVal = SysCmd(acSysCmdUpdateMeter, LeftOver / 1000)
' Read the remaining blocks of data, writing them to the table.
FileData = String$(BlockSize, 32)
For i = 1 To NumBlocks
Get SourceFile, , FileData
T(sField).AppendChunk (FileData)
RetVal = SysCmd(acSysCmdUpdateMeter, BlockSize * i / 1000)
Next i
' Update the record and terminate function.
T.Update
RetVal = SysCmd(acSysCmdRemoveMeter)
Close SourceFile
ReadBLOB = FileLength
Exit Function
Err_ReadBLOB:
ReadBLOB = -Err
Exit Function
End Function
'**************************************************************
' FUNCTION: WriteBLOB()
'
' PURPOSE:
' Writes BLOB information stored in the specified table and field
' to the specified disk file.
'
' PREREQUISITES:
' The specified table with the OLE object field containing the
' binary data must be opened in Visual Basic code and the correct
' record navigated to prior to calling the WriteBLOB() function.
'
' ARGUMENTS:
' T - The table object containing the binary information.
' sField - The OLE object field in table T containing the
' binary information to write.
' Destination - The path and filename to write the binary
' information to.
'
' RETURN:
' The number of bytes written to the destination file.
'**************************************************************
Function WriteBLOB(T As DAO.Recordset, sField As String, _
Destination As String)
Dim NumBlocks As Integer, DestFile As Integer, i As Integer
Dim FileLength As Long, LeftOver As Long
Dim FileData As String
Dim RetVal As Variant
On Error GoTo Err_WriteBLOB
' Get the size of the field.
FileLength = T(sField).FieldSize()
If FileLength = 0 Then
WriteBLOB = 0
Exit Function
End If
' Calculate number of blocks to write and leftover bytes.
NumBlocks = FileLength \ BlockSize
LeftOver = FileLength Mod BlockSize
' Remove any existing destination file.
DestFile = FreeFile
Open Destination For Output As DestFile
Close DestFile
' Open the destination file.
Open Destination For Binary As DestFile
' SysCmd is used to manipulate the status bar meter.
RetVal = SysCmd(acSysCmdInitMeter, _
"Writing BLOB", FileLength / 1000)
' Write the leftover data to the output file.
FileData = T(sField).GetChunk(0, LeftOver)
Put DestFile, , FileData
' Update the status bar meter.
RetVal = SysCmd(acSysCmdUpdateMeter, LeftOver / 1000)
' Write the remaining blocks of data to the output file.
For i = 1 To NumBlocks
' Reads a chunk and writes it to output file.
FileData = T(sField).GetChunk((i - 1) * BlockSize _
+ LeftOver, BlockSize)
Put DestFile, , FileData
RetVal = SysCmd(acSysCmdUpdateMeter, _
((i - 1) * BlockSize + LeftOver) / 1000)
Next i
' Terminates function
RetVal = SysCmd(acSysCmdRemoveMeter)
Close DestFile
WriteBLOB = FileLength
Exit Function
Err_WriteBLOB:
WriteBLOB = -Err
Exit Function
End Function
'**************************************************************
' SUB: CopyFile
'
' PURPOSE:
' Demonstrates how to use ReadBLOB() and WriteBLOB().
'
' PREREQUISITES:
' A table called BLOB that contains an OLE Object field called
' Blob.
'
' ARGUMENTS:
' Source - The path and filename of the information to copy.
' Destination - The path and filename of the file to write
' the binary information to.
'
' EXAMPLE:
' CopyFile "c:\windows\winfile.hlp", "c:\windows\winfil_1.hlp"
'**************************************************************
Sub CopyFile(Source As String, Destination As String)
Dim BytesRead As Variant, BytesWritten As Variant
Dim Msg As String
Dim db As DAO.Database
Dim T As DAO.Recordset
' Open the BLOB table.
Set db = CurrentDb()
Set T = db.OpenRecordset("BLOB", dbOpenTable)
' Create a new record and move to it.
T.AddNew
T.Update
T.MoveLast
BytesRead = ReadBLOB(Source, T, "Blob")
Msg = "Finished reading """ & Source & """"
Msg = Msg & Chr$(13) & ".. " & BytesRead & " bytes read."
MsgBox Msg, 64, "Copy File"
BytesWritten = WriteBLOB(T, "Blob", Destination)
Msg = "Finished writing """ & Destination & """"
Msg = Msg & Chr$(13) & ".. " & BytesWritten & " bytes written."
MsgBox Msg, 64, "Copy File"
End Sub
Last edited by si_the_geek; Sep 30th, 2010 at 12:41 PM.
Reason: added Code tags
< advertising removed by moderator >
Posting Permissions
- You may not post new threads
- You may not post replies
- You may not post attachments
- You may not edit your posts
-
Forum Rules
|
Click Here to Expand Forum to Full Width
|