Pass 2D-Array by Ref/Pointer

Hi guys,

I am trying to pass a 2D Byte Array by pointer from VB 6 to C++ DLL for faster processing.

Here is the VB code i'm using:

Code:

Private Declare Function ImageBrightness Lib "ipong.dll" (ByRef lpDib As Any, uBPSL As Long, uHeight As Long, Value As Long) As Long

Private Sub Command1_Click()
    Dim bDib() As Byte
    ReDim bDib(5, 1)
    bDib(0, 0) = 255
    bDib(1, 0) = 255
    bDib(2, 0) = 255
    bDib(3, 0) = 0
    bDib(4, 0) = 0
    bDib(5, 0) = 255
    bDib(0, 1) = 0
    bDib(1, 1) = 255
    bDib(2, 1) = 0
    bDib(3, 1) = 255
    bDib(4, 1) = 0
    bDib(5, 1) = 0
    Call ImageBrightness(bDib(0, 0), 6, 2, 0)
End Sub

And here is my c code (although the algorithm does invert not brightness)...

Code:

#include "stdafx.h"
#include "resource.h"
#include "windows.h"
#include "oleauto.h"

BOOL __declspec (dllexport) __stdcall ImageBrightness(BYTE **bDib, UINT uBPSL, UINT uHeight, UINT Value);


HINSTANCE ghInst;

int APIENTRY DllMain(HINSTANCE hModule, DWORD ul_reason_for_call, LPVOID lpReserved)
{
	if (ul_reason_for_call == DLL_PROCESS_ATTACH)
		ghInst = hModule; 
	return TRUE;
}

BOOL __declspec (dllexport) __stdcall ImageBrightness(BYTE **bDib, UINT uBPSL, UINT uHeight, UINT Value)
{

	UINT nW, nH;
	nW = uBPSL - 2;
	nH = uHeight - 1;
	
	UINT x, y, x_1, x_2;

	for(x=0;x<nW;x=x+3)
	{
		for(y=0;y<nH;y++)
		{
			x_1 = x + 1;
			x_2 = x + 2;
			//Invert each byte
			bDib[x_2][y] = 255 - bDib[x_2][y];
			bDib[x_1][y] = 255 - bDib[x_1][y];
			bDib[x][y]   = 255 - bDib[x][y];

		}
	}

	return true;

}

When i call the ImageBrightness function my vb executable crashes. I understand how pointers work but not completely sure how to deal with this scenario. Any help would be much appreciated.

Cheers
option

In you'r ImageBrightness(), put MessageBox() calls all over it, to see where it crashes; So you know where the problem is.

However, just by looking at it, I would say you are trying to I/O beyond your matrix' size. In C/C++ I know that you will crash you'r program very easily if you try.