The problem on the font of Korean

Fisrt, I can't use English well.Sorry.

^^;

Our site is Korean site.
We have the program to convert the text to the image.
But we do not go well.
The letter all is seen as the square.(Font Problem??)


Please!! gives the resolution.

view this problem
http://www.rikkyouniv.net/_Tools/Read_Mail.aspx?UserId=karma&MgId=7A1E85395F356B6DFB687506D0730150

the code
====================================
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim UserId As String
Dim MgId As String

UserId = Request.QueryString("UserId")
MgId = Request.QueryString("MgId")


Dim _dbconn As New RikkyoUniv.DbConn
Dim stc_db As RikkyoUniv.Stc.stc_SqlDb
_dbconn.Active(stc_db)
stc_db.DbCommand.CommandType = CommandType.StoredProcedure
stc_db.DbCommand.CommandText = "Pr_Read_KoreanMail"
stc_db.DbCommand.Parameters.Add("@UserId", SqlDbType.VarChar).Value = UserId
stc_db.DbCommand.Parameters.Add("@MgId", SqlDbType.VarChar).Value = MgId

stc_db.DbReader = stc_db.DbCommand.ExecuteReader

If stc_db.DbReader.Read Then
Write_Text((stc_db.DbReader("MailContent")))

End If

_dbconn.deActive(stc_db)
End Sub

Private Sub Write_Text(ByVal Str As String)

Dim bmp As Bitmap = New Bitmap(300, 400)
Dim g As Graphics = Graphics.FromImage(bmp)
g.Clear(Color.White)


Dim f As Font = New Font("gulim", 8)

Dim mybrush As SolidBrush = New SolidBrush(Color.Black)

g.DrawString(Str, f, mybrush, 0, 0)

Response.Clear()
Response.ContentType = "image/gif"
bmp.Save(Response.OutputStream, Imaging.ImageFormat.Gif)

bmp.Dispose()
g.Dispose()


End Sub