How to split bitmap byte array into 4 byte array to create 4 image?

Question

Hi,

I got bitmap bit array using CreateDIBSection().How to split bitmap byte array into 4 byte array to create 4 image?

Answer 1

I did a test with 4 DIB Sections, but as said in other threads, it is simpler with GDI+ or WIC =>

HBITMAP hBitmap = (HBITMAP)LoadImage(NULL, L"E:\\Butterfly_Blue.bmp", IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE | LR_CREATEDIBSECTION);  
DIBSECTION ds;  
GetObject(hBitmap, sizeof(ds), &ds);  
  
BYTE* pBits = (BYTE*)ds.dsBm.bmBits;  
BYTE* pScan = pBits;  
int nWidth = ds.dsBm.bmWidth;  
int nHeight = ds.dsBm.bmHeight;  
long cbScan = ((nWidth * 24 + 31) & ~31) / 8;  
  
SIZE sz;  
sz.cx = nWidth / 2;  
sz.cy = nHeight / 2;  
  
BYTE* pbBitmap1;  
HBITMAP hBitmap1 = NULL;  
HRESULT hr = CreateNBitHBITMAP(NULL, &sz, (void**)&pbBitmap1, &hBitmap1, 24);  
  
BYTE* pbBitmap2;  
HBITMAP hBitmap2 = NULL;  
hr = CreateNBitHBITMAP(NULL, &sz, (void**)&pbBitmap2, &hBitmap2, 24);  
  
BYTE* pbBitmap3;  
HBITMAP hBitmap3 = NULL;  
hr = CreateNBitHBITMAP(NULL, &sz, (void**)&pbBitmap3, &hBitmap3, 24);  
  
BYTE* pbBitmap4;  
HBITMAP hBitmap4 = NULL;  
hr = CreateNBitHBITMAP(NULL, &sz, (void**)&pbBitmap4, &hBitmap4, 24);  
  
BYTE* pScan1 = pbBitmap1;  
long cbScan1 = ((nWidth/2 * 24 + 31) & ~31) / 8;  
  
BYTE* pScan2 = pbBitmap2;  
long cbScan2 = ((nWidth/2 * 24 + 31) & ~31) / 8;  
  
BYTE* pScan3 = pbBitmap3;  
long cbScan3 = ((nWidth/2 * 24 + 31) & ~31) / 8;  
  
BYTE* pScan4 = pbBitmap4;  
long cbScan4 = ((nWidth/2 * 24 + 31) & ~31) / 8;  
  
for (int nY = 0; nY < nHeight; ++nY)  
{  
	for (int nX = 0; nX < nWidth; ++nX)  
	{  
		// Top Left  
		if (nY > nHeight / 2 && nX < nWidth / 2)  
		{  
			pScan1[0] = pScan[0];  
			pScan1[1] = pScan[1];  
			pScan1[2] = pScan[2];  
			// Test Red BGR  
			// pScan1[2] = 255;  
			pScan1 += 3;  
		}  
  
		// Top Right  
		if (nY > nHeight / 2 && nX > nWidth / 2)  
		{  
			pScan2[0] = pScan[0];  
			pScan2[1] = pScan[1];  
			pScan2[2] = pScan[2];  
			// Test Green BGR  
			// pScan2[1] = 255;  
			pScan2 += 3;  
		}  
  
		// Bottom Left  
		if (nY < nHeight / 2 && nX < nWidth / 2)  
		{  
			pScan3[0] = pScan[0];  
			pScan3[1] = pScan[1];  
			pScan3[2] = pScan[2];  
			// Test Blue BGR  
			// pScan3[0] = 255;  
			pScan3 += 3;  
		}  
  
		// Bottom Right  
		if (nY < nHeight / 2 && nX > nWidth / 2)  
		{  
			pScan4[0] = pScan[0];  
			pScan4[1] = pScan[1];  
			pScan4[2] = pScan[2];  
			// Test Yellow BGR  
			/* pScan4[1] = 255;  
			pScan4[2] = 255; */  
			pScan4 += 3;  
		}  
  
		// Next pixel  
		pScan += 3;  
	}  
	// Next scan line  
	pBits += cbScan;  
	pScan = pBits;  
  
	// Top  
	if (nY > nHeight / 2)  
	{  
		pbBitmap1 += cbScan1;  
		pScan1 = pbBitmap1;  
  
		pbBitmap2 += cbScan2;  
		pScan2 = pbBitmap2;  
	}  
  
	// Bottom  
	if (nY < nHeight / 2)  
	{  
		pbBitmap3 += cbScan3;  
		pScan3 = pbBitmap3;  
  
		pbBitmap4 += cbScan4;  
		pScan4 = pbBitmap4;  
	}					  
}  
  
// Test display on screen  
HDC hDC = GetDC(NULL);  
HDC hDCMem = CreateCompatibleDC(hDC);  
int nX = 200, nY = 200, nSpace = 50;  
  
HBITMAP hBitmapOld;  
hBitmapOld = (HBITMAP)SelectObject(hDCMem, hBitmap);  
BitBlt(hDC, nX, nY, nWidth, nHeight, hDCMem, 0, 0, SRCCOPY);  
SelectObject(hDCMem, hBitmapOld);  
DeleteObject(hBitmap);  
  
hBitmapOld = (HBITMAP)SelectObject(hDCMem, hBitmap1);  
BitBlt(hDC, nX + nWidth + nSpace, nY, nWidth / 2, nHeight / 2, hDCMem, 0, 0, SRCCOPY);  
SelectObject(hDCMem, hBitmapOld);  
DeleteObject(hBitmap1);  
  
hBitmapOld = (HBITMAP)SelectObject(hDCMem, hBitmap2);  
BitBlt(hDC, nX + nWidth + nSpace + nWidth/2 + nSpace, nY, nWidth / 2, nHeight / 2, hDCMem, 0, 0, SRCCOPY);  
SelectObject(hDCMem, hBitmapOld);  
DeleteObject(hBitmap2);  
  
hBitmapOld = (HBITMAP)SelectObject(hDCMem, hBitmap3);  
BitBlt(hDC, nX + nWidth + nSpace, nY + nHeight/2 + nSpace, nWidth / 2, nHeight / 2, hDCMem, 0, 0, SRCCOPY);  
SelectObject(hDCMem, hBitmapOld);  
DeleteObject(hBitmap3);  
  
hBitmapOld = (HBITMAP)SelectObject(hDCMem, hBitmap4);  
BitBlt(hDC, nX + nWidth + nSpace + nWidth / 2 + nSpace, nY +  nHeight / 2 + nSpace, nWidth / 2, nHeight / 2, hDCMem, 0, 0, SRCCOPY);  
SelectObject(hDCMem, hBitmapOld);  
DeleteObject(hBitmap4);  
  
DeleteDC(hDCMem);  
ReleaseDC(NULL, hDC);  

Utility Function :

// Adapted from MS SDK  
HRESULT CreateNBitHBITMAP(HDC hDC, const SIZE* psize, void** ppvBits, HBITMAP* phBitmap, WORD nBitCount)  
{  
	*phBitmap = NULL;  
	BITMAPINFO bmi = { 0 };  
	bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);  
	bmi.bmiHeader.biWidth = psize->cx;  
	bmi.bmiHeader.biHeight = psize->cy;  
	bmi.bmiHeader.biPlanes = 1;  
	bmi.bmiHeader.biBitCount = nBitCount;  
	bmi.bmiHeader.biCompression = BI_RGB;  
	HDC hDCUsed = hDC ? hDC : GetDC(NULL);  
	if (hDCUsed)  
	{  
		*phBitmap = CreateDIBSection(hDCUsed, &bmi, DIB_RGB_COLORS, ppvBits, NULL, 0);  
		if (hDC != hDCUsed)  
		{  
			ReleaseDC(NULL, hDCUsed);  
		}  
	}  
	return (NULL == *phBitmap) ? E_OUTOFMEMORY : S_OK;  
}