Pass 2D-Array by Ref/Pointer

[option]

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:

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)...

#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

[Queatrix]

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.