This project is a simple example of using the "WinRT OCR Engine" to recognize the text from a PictureBox image pulled from the Clipboard. Just copy any image containing some text in the Clipboard and click on the PictureBox to display it. The recognized text will appear in the TextBox below.
The code is fairly simple, the biggest hurdle to overcome was that the OCR Engine doesn't work with regular GDI bitmaps but uses "SoftwareBitmap" objects instead. So all we had to do was create such an object and then go through a bunch of interfaces just to expose the underlying byte buffer. Once we got that, it all came down to calling "GetDIBits" on the PictureBox picture handle to pull the bitmap bytes into the "SoftwareBitmap" object and let the OCR Engine do its magic. That meant calling the "RecognizeAsync" method and raising an event when the asynchronous operation was completed (which is pretty much instant).
frmOCR.frm
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It seems the more you crank up the picture contrast the better results you get on the text recognition. Best results would be from an image containing black text over a white background.
Here is the demo project: OCR.ZIP
The code is fairly simple, the biggest hurdle to overcome was that the OCR Engine doesn't work with regular GDI bitmaps but uses "SoftwareBitmap" objects instead. So all we had to do was create such an object and then go through a bunch of interfaces just to expose the underlying byte buffer. Once we got that, it all came down to calling "GetDIBits" on the PictureBox picture handle to pull the bitmap bytes into the "SoftwareBitmap" object and let the OCR Engine do its magic. That meant calling the "RecognizeAsync" method and raising an event when the asynchronous operation was completed (which is pretty much instant).
frmOCR.frm
Code:
Option Explicit
Private Type BITMAP
bmType As Long
bmWidth As Long
bmHeight As Long
bmWidthBytes As Long
bmPlanes As Integer
bmBitsPixel As Integer
bmBits As Long
End Type
Private Type BITMAPINFOHEADER
biSize As Long
biWidth As Long
biHeight As Long
biPlanes As Integer
biBitCount As Integer
biCompression As Long
biSizeImage As Long
biXPelsPerMeter As Long
biYPelsPerMeter As Long
biClrUsed As Long
biClrImportant As Long
End Type
Private Type RGBQUAD
rgbBlue As Byte
rgbGreen As Byte
rgbRed As Byte
rgbReserved As Byte
End Type
Private Type BITMAPINFO
bmiHeader As BITMAPINFOHEADER
bmiColors As RGBQUAD
End Type
Private Const DIB_RGB_COLORS As Long = 0
Private Declare Function GetDIBits Lib "gdi32" (ByVal hDC As Long, ByVal hBitmap As Long, ByVal lStart As Long, ByVal cLines As Long, ByVal lpvBits As Long, ByVal lpBMI As Long, ByVal lUsage As Long) As Long
Private Declare Function GetObjectW Lib "gdi32" (ByVal hGDIObj As Long, ByVal cbBuffer As Long, ByVal lpvObject As Long) As Long
Private WithEvents objOCR As cOCR, objSoftwareBitmap As cSoftwareBitmap, bmiBitmapInfo As BITMAPINFO
Private Sub Form_Load()
With bmiBitmapInfo.bmiHeader: .biSize = LenB(bmiBitmapInfo.bmiHeader): .biPlanes = 1: .biBitCount = 32: End With
Set objSoftwareBitmap = New cSoftwareBitmap: Set objOCR = New cOCR
End Sub
Private Sub objOCR_GetText(sText As String)
txtOCR = sText
End Sub
Private Sub picOCR_Click()
Dim bmBitmap As BITMAP
If Clipboard.GetFormat(vbCFBitmap) Then
With picOCR
Set .Picture = Clipboard.GetData
GetObjectW .Picture.Handle, LenB(bmBitmap), VarPtr(bmBitmap)
.Width = .ScaleX(bmBitmap.bmWidth, vbPixels, .ScaleMode): .Height = .ScaleY(bmBitmap.bmHeight, vbPixels, .ScaleMode)
txtOCR.Move .Left, .Top + .Height, .Width: Width = Width - ScaleWidth + .Left * 2 + .Width: Height = Height - ScaleHeight + .Height + txtOCR.Height + .Top * 2
With bmiBitmapInfo.bmiHeader: .biWidth = bmBitmap.bmWidth: .biHeight = -bmBitmap.bmHeight: End With
If objSoftwareBitmap.CreateSoftwareBitmap(bmBitmap.bmWidth, bmBitmap.bmHeight) Then
GetDIBits .hDC, .Picture.Handle, 0, bmBitmap.bmHeight, objSoftwareBitmap.GetBitmapBuffer, VarPtr(bmiBitmapInfo), DIB_RGB_COLORS
objSoftwareBitmap.UnlockBitmapBuffer
objOCR.RecognizeAsync objSoftwareBitmap
End If
End With
Else
MsgBox "Clipboard does not contain a picture!", vbInformation, App.Title
End If
End SubIt seems the more you crank up the picture contrast the better results you get on the text recognition. Best results would be from an image containing black text over a white background.
Here is the demo project: OCR.ZIP