Unable to read image file correctly that was written using vb6.0

  • Thread starter Thread starter udit_handa
  • Start date Start date
U

udit_handa

I am facing a strange problem I ahve a datadase which stores tiff
images using Image datatype in Sql server.
These images are written using a Vb6.0 desktop application with the
following code

==================VB Code====================================
Open strFile For Binary Access Read As #(iFile)
ImageSize = LOF(iFile)
lngNumChunks = ImageSize / 4096
lngOff = ImageSize Mod 4096
strData = String(4096, "0")
For i = 1 To lngNumChunks
strData = String(4096, "0")
Get #(iFile), , strData
rs.Fields("Img").AppendChunk strData
Next
If lngOff > 0 Then
strData = String(lngOff, "0")
Get #(iFile), , strData
rs.Fields("Img").AppendChunk strData
End If
Close #(iFile)
====================VB Code==================================
It works fine when i read it with a VB6.0 application but i have tried
my level best without sucess to read this image file in Dot net.
A sample code that i last tried is as follows


=========Dot Net C# code===========================
SqlCommand cmd=new SqlCommand();
SqlDataReader rdr;
cmd.CommandType=CommandType.Text ;
cmd.CommandText="select img from tblDAllImages where Active = 1 and ID
=1135";
cmd.Connection=con;
con.Open ();
rdr=cmd.ExecuteReader();
System.IO.FileStream fs ;//= new System.IO.FileStream("c:\\aa.tif",
System.IO.FileMode.Create, System.IO.FileAccess.Write);
BinaryWriter bw ;
int BufferSize=100;
byte[] b =new byte[BufferSize];
long retval,startindex=0;
for(int i=0;i<b.Length ;i++)
Response.Write(b);
Response.Write(b.Length);
if (rdr.Read())
{
fs = new FileStream("c:\\aaa11.tif" , FileMode.OpenOrCreate,
FileAccess.Write) ;
bw = new BinaryWriter(fs) ;
startindex = 0 ;
retval = rdr.GetBytes(0 , startindex, b, 0, BufferSize) ;
while( retval == BufferSize )
{
bw.Write(b) ;
bw.Flush();
startindex = startindex + BufferSize;
retval = rdr.GetBytes(0, startindex, b, 0, BufferSize) ;
}
bw.Write(b) ;
bw.Flush();
bw.Close() ;
fs.Close();
}

=========Dot Net C# code===========================
This file gets created but is corrupted.It is almost double the size of
the VB6.0 file.
I guess it is something retated to conversion between byte and string
type but i have even tried to convert the byte to a string and then
save it.
Any help is welcome
Thanks
 
Udit,

Some pictures have headers.
what can mean that the startingpoint is 78 while you have to decrement the
buffersize with that.

I hope this helps,

Cor
 
Hi ,
Thanks for the reply but i am able to create images using VB code
without considering any headers.


======SaveImage===========
ImageSize = LOF(iFile)
lngNumChunks = ImageSize / 4096
lngOff = ImageSize Mod 4096
strData = String(4096, "0")
For i = 1 To lngNumChunks
strData = String(4096, "0")
Get #(iFile), , strData
rs.Fields("Img").AppendChunk strData
Next
If lngOff > 0 Then
strData = String(lngOff, "0")
Get #(iFile), , strData
rs.Fields("Img").AppendChunk strData
End If
Close #(iFile)
======SaveImage===========


===Load Image=============

Open strFile For Binary Access Write As #(iFile)
Set fld = rs.Fields("Img")
ImageSize = fld.ActualSize
lngNumChunks = ImageSize \ 4096
lngOff = ImageSize Mod 4096
If lngOff > 0 Then
strData = String(lngOff, "0")
strData = fld.GetChunk(lngOff)
Put #(iFile), , strData
End If
Do While lngOff < ImageSize
strData = String(4096, "0")
strData = fld.GetChunk(4096)
lngOff = lngOff + 4096
Put #(iFile), , strData
Loop
Close #(iFile)

===Load Image=============

This code always work with VB6.0 without considering the headers.
Could the proble lie it the way the data is first read and written using
a string?

Thanks Udit
 
First, I would simplify how you are getting the data from the database

I do the exact same thing you are doing in some of my apps, which work with
any data type. It should work for you.


System.Data.SqlClient.SqlCommand cmd = new
System.Data.SqlClient.SqlCommand();
System.Data.SqlClient.SqlDataReader rdr;
cmd.CommandType = CommandType.Text ;
cmd.CommandText = "select img from tblDAllImages where Active = 1 and ID
=1135";
cmd.Connection = con;
con.Open ();
rdr = cmd.ExecuteReader();

System.IO.FileStream fs ;

if (rdr.Read())
{

//get the data from the reader
byte[] pData = (byte[])rdr["img"];

//open file for writing
fs = new FileStream("c:\\aaa11.tif" , FileMode.OpenOrCreate,
FileAccess.Write) ;

//write the bytes. (if your file size could be creater than an int can
hold, you'll have to loop.
fs.Write(pData,0,pData.Length);

fs.Close();

}
rdr.Close();


I am facing a strange problem I ahve a datadase which stores tiff
images using Image datatype in Sql server.
These images are written using a Vb6.0 desktop application with the
following code

==================VB Code====================================
Open strFile For Binary Access Read As #(iFile)
ImageSize = LOF(iFile)
lngNumChunks = ImageSize / 4096
lngOff = ImageSize Mod 4096
strData = String(4096, "0")
For i = 1 To lngNumChunks
strData = String(4096, "0")
Get #(iFile), , strData
rs.Fields("Img").AppendChunk strData
Next
If lngOff > 0 Then
strData = String(lngOff, "0")
Get #(iFile), , strData
rs.Fields("Img").AppendChunk strData
End If
Close #(iFile)
====================VB Code==================================
It works fine when i read it with a VB6.0 application but i have tried
my level best without sucess to read this image file in Dot net.
A sample code that i last tried is as follows


=========Dot Net C# code===========================
SqlCommand cmd=new SqlCommand();
SqlDataReader rdr;
cmd.CommandType=CommandType.Text ;
cmd.CommandText="select img from tblDAllImages where Active = 1 and ID
=1135";
cmd.Connection=con;
con.Open ();
rdr=cmd.ExecuteReader();
System.IO.FileStream fs ;//= new System.IO.FileStream("c:\\aa.tif",
System.IO.FileMode.Create, System.IO.FileAccess.Write);
BinaryWriter bw ;
int BufferSize=100;
byte[] b =new byte[BufferSize];
long retval,startindex=0;
for(int i=0;i<b.Length ;i++)
Response.Write(b);
Response.Write(b.Length);
if (rdr.Read())
{
fs = new FileStream("c:\\aaa11.tif" , FileMode.OpenOrCreate,
FileAccess.Write) ;
bw = new BinaryWriter(fs) ;
startindex = 0 ;
retval = rdr.GetBytes(0 , startindex, b, 0, BufferSize) ;
while( retval == BufferSize )
{
bw.Write(b) ;
bw.Flush();
startindex = startindex + BufferSize;
retval = rdr.GetBytes(0, startindex, b, 0, BufferSize) ;
}
bw.Write(b) ;
bw.Flush();
bw.Close() ;
fs.Close();
}

=========Dot Net C# code===========================
This file gets created but is corrupted.It is almost double the size of
the VB6.0 file.
I guess it is something retated to conversion between byte and string
type but i have even tried to convert the byte to a string and then
save it.
Any help is welcome
Thanks
Click to expand...
 
I tried every example but it wont read the image properly.
My code works fine with the Category table Picture column in Northwind
Database .But not with the one I use.
For now I made a small VB6.0 component to create a file from the image
field and it works fine but still i would like to use as Dot net code.
My VB6.0 component code is as follows

Public Sub CreateImage(ByVal ImageID As Long, ByVal FileName As String)
Dim con As New ADODB.Connection
con.Open Me.ConnectionString
Dim rs As New ADODB.Recordset, iFile As Integer, i As Integer,
strFile1 As String
Dim fld As ADODB.Field, ImageSize As Long, strData As String,
bytChunk() As Byte
Dim lngNumChunks As Long, lngOff As Long, strFile As String
rs.Open "select * from tblDAllImages where Active = 1 and ID = " &
ImageID, con, adOpenKeyset, adLockOptimistic
If rs.EOF = False Then
iFile = FreeFile
Open FileName For Binary Access Write As #(iFile)
Set fld = rs.Fields("Img")
ImageSize = fld.ActualSize
lngNumChunks = ImageSize \ 4096
lngOff = ImageSize Mod 4096
If lngOff > 0 Then
strData = String(lngOff, "0")
strData = fld.GetChunk(lngOff)
Put #(iFile), , strData
End If
Do While lngOff < ImageSize
strData = String(4096, "0")
strData = fld.GetChunk(4096)
lngOff = lngOff + 4096
Put #(iFile), , strData
Loop
Close #(iFile)
End If
If rs.State = adStateOpen Then rs.Close
Set rs = Nothing
End Sub

Thanks
Udit
 
Udit,

You did try the sample without the 78 offset as well

I don't know almost no classic Ado code more. So with that it seems for me
not helpful to help you.

Cor
 
Hi,
I did tried the 78 bit ofset and it works fine for the northwind
database images but not for mine.
I hope there is a solution somewhere.
thanks Udit
 
Udit,

I would not know, it should have to do how your images are written. I see no
reply from Paul who mostly replies on these messages as it is ado -> adonet,
so it will be hard to go.

What you can try is using the newsgroup

microsoft.public.dotnet.languages.vb

I give you few change, however you never know

Cor
 
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