Binary streaming of large images from Database

' This file contains just two functions
' 1. GetImageFromDB
' 2. DownloadImage
'
' Place these 2 functions inside ur vb file in ur asp.net application.
' Please make appropriate changes to suit ur application needs

    ' This function returns the image retrieved from the database
    Private Function GetImageFromDB(ByVal ImageID As Integer) As Image

        ' Get the Connection string
        Dim strConnection As String
        strConnection = "Specify Connection string here"

        Dim conn As New SqlConnection(strConnection)
        Dim sqlCommand As String
        Dim strImage As String
        Dim image As Image

        Try
            sqlCommand = "SELECT Image FROM ImageTable WHERE ImageID = " + ImageID.ToString

            Dim cmd As New SqlCommand(sqlCommand)
            cmd.Connection = conn
            conn.Open()
            Dim dr As SqlDataReader
            dr = cmd.ExecuteReader()
            While (dr.Read())

                Dim byt As Byte()
                byt = dr.Item(strImage)
                Dim bmp As New Bitmap(New System.IO.MemoryStream(byt))
                image = bmp

            End While
        Catch ex As Exception
            ' Log Error
            Response.Write(ex.Message)
        Finally
            If conn.State = ConnectionState.Open Then
                conn.Close()
            End If
        End Try

        Return image

    End Function


    ' Download the image on to the client
    Public Sub DownloadImage(ByVal ImageID As Integer)

        Dim image As Image
        Dim bmpNew As Bitmap
        Dim imageNew As Image
        Dim objGraphics As Graphics

        Dim objFont As Font = New Font("Verdana", 12, FontStyle.Bold)
        Dim objbrush As Brush = Brushes.Black

        Try

            ' Get the Image from DB
            image = GetImageFromDB(ImageID)


            Try
                objGraphics = Graphics.FromImage(image)
            Catch e As Exception
                ' The image is in indexed pixel format
                ' Create a temp bitmap

                bmpNew = New Bitmap(image.Width, image.Height)
                imageNew = bmpNew

                objGraphics = Graphics.FromImage(imageNew)

                '' Draw the contents of old bitmap to new bitmap	
                objGraphics.DrawImage(image, New Rectangle(0, 0, imageNew.Width, imageNew.Height), _
                                        0, 0, image.Width, image.Height, GraphicsUnit.Pixel)

                image = imageNew

            End Try

            ' writing a simple Text over the image
            Dim rect As New Drawing.RectangleF(10, 10, 200, 50)
            objGraphics.DrawString("Simple Text", objFont, objbrush, rect)

            ' Set the content type and return the image
            Response.ContentType = "image/jpeg"
            'image.Save(Response.OutputStream, ImageFormat.Jpeg)

            Dim ms As MemoryStream = New MemoryStream()
            image.Save(ms, Imaging.ImageFormat.Jpeg)
            Dim bytImage(ms.Length) As Byte
            bytImage = ms.ToArray()
            ms.Close()
            
            ms = New MemoryStream(bytImage)
            Response.Clear()
            Response.AddHeader("Content-Type", "binary/octet-stream")
            Response.AddHeader("Content-Length", bytImage.Length.ToString())
            Response.AddHeader("Content-Disposition", "attachment; filename= DownloadedImage.jpg; size=" + bytImage.Length.ToString())
            Response.Flush()


            Dim chunkSize As Integer = 1024

            Dim i As Integer
            For i = 0 To bytImage.Length Step chunkSize
                If (Not Response.IsClientConnected) Then
                    Exit For
                End If

                Dim size As Integer = chunkSize
                If (i + chunkSize >= bytImage.Length) Then
                    size = (bytImage.Length - i)
                End If

                Dim chunk(size - 1) As Byte
                ms.Read(chunk, 0, size)
                Response.BinaryWrite(chunk)
                Response.Flush()
            Next
            ms.Close()
            bytImage.Clear(bytImage, 0, bytImage.Length)

        Catch ex As Exception
            ' Log exception
            Response.Write(ex.Message)
        Finally

            ' Kill the objects
            bmpNew.Dispose()
            imageNew.Dispose()
            image.Dispose()
            objGraphics.Dispose()

        End Try

    End Sub