How to count black pixels from image in MS Access VBA? - vba

Question

I have capture signatures using Msink Obj control from my form and saved them in signature field in my SQL database and datatype for it is image.
I have converted the saved sign data in to .gif and also shown it in image control in my form but now I want to calculate number of black pixels in this image or count of it.
So please suggest how can I go with it?

Answer 1

I have found an windows API for it which can we used for getting pixel count.
It is GetPixel Lib "gdi32" API below is sample code for it :-
Option Compare Database
'Following Two API'S Are Added To Count The Pixles
Private Declare Function GetPixel Lib "gdi32" (ByVal hdc As Long, ByVal X As Long, ByVal y As Long) As Long
Private Declare Function GetWindowDC Lib "user32" (ByVal hwnd As Long) As Long
Public Function GetPixlesTest(pHwnd As Long) As Integer: On Error Resume Next
Dim i As Long, j As Long, nBlack As Long, nWhite As Long, pHdc As Long, tempColor As Long
Dim count As Integer
count = 0 'Initializing count with 0
With Forms!frmTestSign!imgTest 'Getting Form Image Control
pHdc1 = GetWindowDC(pHwnd)
For i = 0 To .Width
For j = 0 To .Height`enter code here`
tempColor = GetPixel(pHdc1, i, j)
If tempColor = vbBlack Then 'Counting for black pixles only.
nBlack = nBlack + 1
End If
Next
Next
End With
TotalBlack = nBlack - 611 'Substracting 611 becuase it has default 611 black pixle on my form
GetPixlesPractical = TotalBlack
End Function
Calling above function :-
gstrpixlecount = GetPixlesPractical(Me.hwnd) 'Call it on same form in which you have image control to get pixles.
Plesae follow below link for more info :-
http://msdn.microsoft.com/en-us/library/windows/desktop/dd144947(v=vs.85).aspx
http://msdn.microsoft.com/en-us/library/windows/desktop/dd144909(v=vs.85).aspx
http://www.vbdotnetforums.com/graphics-gdi/22565-using-winapi-getpixel.html
Thanks