[Lazarus] View Graphic File

[Antonio Fortuny]

Le 20/02/2014 07:43, Allan E. Registos a écrit :
> Hi all,
>
> A noob question, I have trouble trying to port an existing vb.net 
> snippet to pascal.
> Can anyone provide a code snippet where we can download and view a 
> file from a Database?  A binary(jpeg/pdf file) was uploaded to a 
> database table. The code will just download the file uploaded and view 
> it.
>
> In vb.net this can be done:
>
> /      if conn.State = ConnectionState.Closed Then conn.Open()//
> //            sql = "Select binfile from graphicfiles WHERE id=" & id//
> //
> //            cmd = New NpgsqlCommand(sql, conn)//
> //
> //            Dim fileData As Byte() = DirectCast(cmd.ExecuteScalar(), 
> Byte())//
> //
> //            Dim sTempFileName As String = Path.GetTempPath & "\" & 
> sFileName//
> //
> //            If Not fileData Is Nothing Then//
> //
> //                'Read image data into a file stream //
> //                Using fs As New FileStream(sTempFileName, 
> FileMode.OpenOrCreate, FileAccess.Write)//
> //                    fs.Write(fileData, 0, fileData.Length)//
> //                    'Set image variable value using memory stream. //
> //                    fs.Flush()//
> //                    fs.Close()//
> //                End Using//
> //
> //                Process.Start(sTempFileName) 'Open file//
> //
> //            End If//
> /
Sounds quite easy to translate:
1. install the sqldblaz package if not yet done
2. onto a form or a datamodule drop a connection named DB (correcpondig 
to your DB) and a transaction named TR; link them
3. drop a TSqlQuery, link it to the connection and the transacton just 
dropped (name Q)
4. fill in the Sql property/. /I assume that the column binfile is a 
binay blob
...
var
     fs: TMemoryStream;
begin
...
fs := TMemoryStream.Create;
try
     DB.DatabaseName := 'whatever connection could be';
     DB..UserName := 'sysdba';
     DB.Password := 'your password';
     DB.Connected := True;
     Q.Sql.Text := Format('Select binfile from graphicfiles WHERE 
id=%d/'/, [id]);/        // assuming id is an integer, adapt the format 
otherwise/
     TR.StartTransaction;
     Q.Prepare;
     Q.Open;
     if Q.Eof = False then begin
         fs.Position := 0;
         TBlobField(Q.FieldByName('binfile')).SaveToStream(fs);
         ...
         fs.Position := 0;         // reset position to beginning of stream
         do  whatever you need to do with the stream "fs"
         use stream length by fs.Size
         fs.SaveToFile('any file name');
         // for an image dropped onto a form:
         Image.Picture.LoadFromStream(fs);
         ... etc...

         ...
     end;
     Q.Close;
finally
     TR.Commit
     fs.Free
end

This should work as it is a code snippet used in one of my programs 
(cleaned and simplified). In my case the DBMS is Firebird but this 
should work with any other supported by SqlDbLaz package.

Antonio.

Thanks,,
> Allan
>
>
> --
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