Just add "BarcodeLib.BarcodeReader.dll" into your project reference.
Using Free VB.NET Code to Scan Code 128 Barcode Image
Dim datas() AsString = BarcodeReader.read("c:/code128-vbnet.gif", BarcodeReader.CODE128)
Using the above free sample VB code, you can read & decode all Code 128 barcodes from the gif image file (code128-vbnet).
How to Improve Code 128 Scanning Rate in VB.NET Applications
Activate maxOneBarcodePerPage to true
This property exerts a significant effect in speeding up the scanning rate, especially when you are going to read & decode a maximum Code 128 (which is the only barcode in the source image file).
If this property is false, the Code 128 barcode reader will use total 5 algorithms and each will read the whole source image from 4 directions, so it saves much time if the reader stops scanning once it detects one Code 128 barcode.
Scan & read partial image file
Undoubtedly, it will accelerate the reading speed if users let the reader just scan the Code 128 barcode region, instead of the whole image.
The Code 128 VB.NET barcode reader SDK provided by BarcodeLib.com successfully achieves this by using knowledge of axis. By specifying the most left top point as (0%, 0%) and the most right bottom point as (100%, 100%), our barcode scanner can accurately locate the barcode region. (Let's take top 20% and bottom 20% area as an example.)
Dim setting As OptimizeSetting = New OptimizeSetting()
setMaxOneBarcodePerPage(True)
Dim top20 As ScanArea = New ScanArea(New Drawing.PointF(0.0F, 0.0F), New Drawing.PointF(100.0F, 20.0F))
Dim bottom20 As ScanArea = New ScanArea(New Drawing.PointF(0.0F, 80.0F), New Drawing.PointF(100.0F, 100.0F))
Dim areas As List(Of ScanArea) = New List(Of ScanArea) areas.Add(top20) areas.Add(bottom20)
setting.setAreas(areas)
Dim datas() AsString = BarcodeReader.read("c:/code128-vbnet.gif", BarcodeReader.CODE128, setting)