The idea behind the following algorithm is to rotate the image in steps of 10 degrees. This works, because to detect a barcode only one scan line must be in the interior of the barcode.

This barcode is detected.	This barcode is not detected.

To save some time, the rotation is only done from 0 to 90 degrees. The angles between 90 and 360 can be calculated by applying additional 90 degree rotates.

The algorithm

Public Function ReadBarcodes(ByVal img As gmseBitmap) As gmseBarcodeInfo()
	Dim alpha As Double
	Dim delta As Double = 10
	Dim bcs As gmseBarcodeInfoCollection
	Dim bc As gmseBarcodeInfo
	Dim hash As New Hashtable
	Dim i As Integer
	Dim rotimg As gmseBitmap
	Dim arrbc() As gmseBarcodeInfo

	While alpha < 90
		If alpha = 0 Then
			rotimg = img
		Else
			rotimg = img.Rotate(alpha)
		End If
		For i = 0 To 3
			bcs = rotimg.ReadBarcodes
			AddBarcodesToHash(hash, bcs)
			rotimg.RotateFlip(RotateFlipType.Rotate90FlipNone)
		Next
		alpha += delta
	End While
	ReDim arrbc(hash.Count - 1)
	i = 0
	For Each bc In hash.Values
		arrbc(i) = bc
		i += 1
	Next
	Return arrbc
End Function
	

Algorithms Overview