Code39 Barcodes über ASP.NET (VB) ausgeben

Den folgenden Quelltext habe ich vor etwa 2 Jahren in seiner ursprünglichen Form in einem VBA-Forum gefunden und an VB.NET angepasst um in einer ASP.NET-Anwendung on-the-fly Barcodes auszugeben.
Vorteil von Code39 ist seine große Druck- und Lesetoleranz. Zwischenzeitlich hatte ich den Sourcecode auch einmal in C# umgeschrieben. Dieser ist allerdings bei einem Festplattendefekt verloren gegangen.


Private Function MD_Barcode39(ByVal Barcode As String, ByVal PaintObj As Object, _
ByVal mLeft As Single, ByVal mTop As Single, _
ByVal mWidth As Single, ByVal mHeight As Single)

Dim Nbar As Single, Wbar As Single, Qbar As Single, NextBar As Single
Dim CountX As Single, CountY As Single
Dim Parts As Single, Pix As Single, BarCodePlus As String
Dim Stripes As String, BarType As String
Dim Mx As Single, my As Single, Sx As Single, Sy As Single
Const Nratio = 20, Wratio = 55, Qratio = 35

Dim g As System.Drawing.Graphics
Dim pB As New System.Drawing.SolidBrush(System.Drawing.Color.Black)
Dim pW As New System.Drawing.SolidBrush(System.Drawing.Color.White)
Dim color As System.Drawing.SolidBrush

'Get control size and location properties.
Sx = mLeft
Sy = mTop
Mx = mWidth
my = mHeight

g = PaintObj

'Calculate actual and relative pixels values.
Parts = (Barcode.Length + 2) * ((6 * Nratio) + (3 * Wratio) + (1 * Qratio))
Pix = (Mx / Parts)
Nbar = (20 * Pix)
Wbar = (55 * Pix)
Qbar = (35 * Pix)

'Initialize bar index and color.
NextBar = Sx
color = pW

'Pad each end of string with start/stop characters.
BarCodePlus = "*" &amp; Barcode.ToUpper &amp; "*"

'Walk through each character of the barcode contents.
For CountX = 0 To BarCodePlus.Length - 1
'Get Barcode 1/0 string for indexed character.
Stripes = MD_BC39(BarCodePlus.Substring(CountX, 1))
For CountY = 0 To 8
'For each 1/0, draw a wide/narrow bar.
BarType = Stripes.Substring(CountY, 1)

'Toggle the color (black/white).
If color Is pW Then
color = pB
Else
color = pW
End If

Select Case BarType
Case "1"
'Draw a wide bar.
g.FillRectangle(color, NextBar, Sy, Wbar + NextBar, my + Sy)
NextBar = NextBar + Wbar
Case "0"
'Draw a narrow bar.
g.FillRectangle(color, NextBar, Sy, Nbar + NextBar, my + Sy)
NextBar = NextBar + Nbar
End Select
Next CountY

'Toggle the color (black/white).
If color Is pW Then
color = pB
Else
color = pW
End If

'Draw intermediate "quiet" bar.
g.FillRectangle(color, NextBar, Sy, Qbar + NextBar, my + Sy)
NextBar = NextBar + Qbar
Next CountX
End Function

Function MD_BC39(ByVal CharCode As String) As String
Dim BC39(90) As String

BC39(32) = "011000100" ' space
BC39(36) = "010101000" ' $
BC39(37) = "000101010" ' %
BC39(42) = "010010100" ' * Start/Stop
BC39(43) = "010001010" ' +
BC39(45) = "010000101" ' |
BC39(46) = "110000100" ' .
BC39(47) = "010100010" ' /
BC39(48) = "000110100" ' 0
BC39(49) = "100100001" ' 1
BC39(50) = "001100001" ' 2
BC39(51) = "101100000" ' 3
BC39(52) = "000110001" ' 4
BC39(53) = "100110000" ' 5
BC39(54) = "001110000" ' 6
BC39(55) = "000100101" ' 7
BC39(56) = "100100100" ' 8
BC39(57) = "001100100" ' 9
BC39(65) = "100001001" ' A
BC39(66) = "001001001" ' B
BC39(67) = "101001000" ' C
BC39(68) = "000011001" ' D
BC39(69) = "100011000" ' E
BC39(70) = "001011000" ' F
BC39(71) = "000001101" ' G
BC39(72) = "100001100" ' H
BC39(73) = "001001100" ' I
BC39(74) = "000011100" ' J
BC39(75) = "100000011" ' K
BC39(76) = "001000011" ' L
BC39(77) = "101000010" ' M
BC39(78) = "000010011" ' N
BC39(79) = "100010010" ' O
BC39(80) = "001010010" ' P
BC39(81) = "000000111" ' Q
BC39(82) = "100000110" ' R
BC39(83) = "001000110" ' S
BC39(84) = "000010110" ' T
BC39(85) = "110000001" ' U
BC39(86) = "011000001" ' V
BC39(87) = "111000000" ' W
BC39(88) = "010010001" ' X
BC39(89) = "110010000" ' Y
BC39(90) = "011010000" ' Z

Return BC39(Asc(CharCode))
End Function

Möchte man wie ich die Barcodes in einer ASP.NET-Anwendung ausgeben, kann folgender (schlampiger) Code als kleine Anregung verwendet werden:


Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim barcode As String = Request("barcode")
If Len(barcode) = 0 Then barcode = ""
Dim height As String = Request("height")
If (Len(height) = 0) Or (height > 768) Then height = 75
Dim width As String = Request("width")
If (Len(width) = 0) Or (width > 1024) Then width = 250
Dim plain As Boolean = True
Dim xh, xw As Integer
If Len(Request("plain")) <> 0 Then
If Request("plain") = 1 Then
plain = True
xw = width
xh = height
height = height + 15
Else
plain = False
End If
End If

Dim bmp As New Bitmap(width, height, PixelFormat.Format24bppRgb)

Dim g As Graphics = Graphics.FromImage(bmp)
MD_Barcode39(barcode, g, 0, 0, width, height)

If plain = True Then
Dim dispText As String = barcode
Dim dispFont As New Font("arial", 15, FontStyle.Regular, GraphicsUnit.Pixel)

g.FillRectangle(Brushes.White, 0, xh, xw, 15)

g.DrawString(dispText, dispFont, Brushes.Black, New PointF(0, xh))
End If

bmp.Save(Response.OutputStream, ImageFormat.Jpeg)
bmp.Dispose()
Response.End()
End Sub

In die @Page-Direktive muss noch ContentType=”image/jpeg” hinzugefügt werden:


<%@ Page Language="VB" ContentType="image/jpeg" AutoEventWireup="true" CodeFile="barcode.aspx.vb" Inherits="barcode" %>

Aufrufen kann man das Dokument anschließend über den lokalen Webserver oder einen (externen) IIS. Der Aufruf vom Bild oben lautet:

http://localhost:12384/barcode.aspx?barcode=1234567890&width=400&plain=1

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