The 'GetBits' function retrieves the bytes of a given HBITMAP handle. The same functionality is usually achieved with the 'GetDIBits' method of GDI. Windows CE does not support the 'GetDIBits' method. The 'GetBits' method can be improved.

GetHBITMAPBytes.cpp

#include <windows.h>

HBITMAP  WINAPI GetBits(HBITMAP h, LONG width, LONG height, WORD bitCount, BYTE **bytes, DWORD *bytesLen)
{
	// Sanity check omitted. 

	HDC hdcScreen;
	hdcScreen = GetDC(NULL);
	if (hdcScreen == NULL) 
	{
		*bytes = NULL;
		*bytesLen = 0;
		return NULL;
	}

	HDC hdcMemoryDCOfFileBitmap;
	hdcMemoryDCOfFileBitmap = CreateCompatibleDC(hdcScreen);
	if (hdcMemoryDCOfFileBitmap == NULL) {
		DeleteDC(hdcScreen);

		*bytes = NULL;
		*bytesLen = 0;
		return 0;
	}

	SelectObject(hdcMemoryDCOfFileBitmap, h);

	HDC hdcMemoryDCOfDIBSection;
	hdcMemoryDCOfDIBSection = CreateCompatibleDC(hdcScreen);
	if (hdcMemoryDCOfDIBSection == NULL) {
		DeleteDC(hdcScreen);
		DeleteDC(hdcMemoryDCOfFileBitmap);

		*bytes = NULL;
		*bytesLen = 0;
		return NULL;
	}

	BITMAPINFO bmi;
	ZeroMemory(&bmi, sizeof bmi);
	bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	bmi.bmiHeader.biWidth = width;
	bmi.bmiHeader.biHeight = (-1) * height;
	bmi.bmiHeader.biPlanes = 1;
	bmi.bmiHeader.biBitCount = bitCount;
	bmi.bmiHeader.biCompression = BI_RGB;

	DWORD bytes_per_scanLine = ((((bmi.bmiHeader.biWidth * bmi.bmiHeader.biBitCount) + 31) / 32) * 4);
	//LONG pad_per_scanLine = bytes_per_scanLine - (((m_BitInfo.bmiHeader.biWidth * m_BitInfo.bmiHeader.biBitCount) + 7) / 8);
	bmi.bmiHeader.biSizeImage = bytes_per_scanLine * abs(bmi.bmiHeader.biHeight);

	BYTE *pixelBuffer;
	HBITMAP hbmp;
	hbmp = CreateDIBSection(hdcScreen, &bmi, DIB_RGB_COLORS, reinterpret_cast<void **>(&pixelBuffer), NULL, 0);
	if (hbmp == NULL) {
		DeleteDC(hdcScreen);
		DeleteDC(hdcMemoryDCOfFileBitmap);
		DeleteDC(hdcMemoryDCOfDIBSection);

		*bytes = NULL;
		*bytesLen = 0;
		return NULL;
	}

	HBITMAP oldBmp;
	oldBmp = HBITMAP(SelectObject(hdcMemoryDCOfDIBSection, hbmp));
	if (oldBmp == NULL) {
		DeleteDC(hdcScreen);
		DeleteDC(hdcMemoryDCOfFileBitmap);
		DeleteDC(hdcMemoryDCOfDIBSection);
		DeleteObject(hbmp);

		*bytes = NULL;
		*bytesLen = 0;
		return NULL;
	}

	BOOL success = BitBlt(hdcMemoryDCOfDIBSection, 0, 0, width, height, hdcMemoryDCOfFileBitmap, 0, 0, SRCCOPY);
	if(FALSE != success)
	{
		*bytes = reinterpret_cast<BYTE*>( *pixelBuffer);
		*bytesLen = bmi.bmiHeader.biSizeImage;
	}
	else
	{
		*bytes = NULL;
		*bytesLen = 0;
		DeleteObject(hbmp);
		hbmp = NULL;
	}


	DeleteDC(hdcScreen);
	DeleteDC(hdcMemoryDCOfFileBitmap);
	DeleteDC(hdcMemoryDCOfFileBitmap);
	DeleteDC(hdcMemoryDCOfDIBSection);

	return hbmp;
}