Function HBitmapToWriteableBitmap

FastCopy/ImageUtils.cpp:39–109

}

winrt::Microsoft::UI::Xaml::Media::Imaging::WriteableBitmap HBitmapToWriteableBitmap(HBITMAP hBitmap, HBITMAP hMask)
{
	// Get the screen DC
	HDC dc = GetDC(NULL);

	// Get icon size info
	BITMAP bm = { 0 };
	GetObject(hBitmap, sizeof(BITMAP), &bm);
	if (bm.bmWidth == 0 || bm.bmHeight == 0)
		return nullptr;

	// Set up BITMAPINFO
	BITMAPINFO bmi = { 0 };
	bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	bmi.bmiHeader.biWidth = bm.bmWidth;
	bmi.bmiHeader.biHeight = -bm.bmHeight;
	bmi.bmiHeader.biPlanes = 1;
	bmi.bmiHeader.biBitCount = 32;
	bmi.bmiHeader.biCompression = BI_RGB;

	// Extract the color bitmap
	int nBits = bm.bmWidth * bm.bmHeight;
	auto colorBits = std::make_unique<int32_t[]>(nBits);
	GetDIBits(dc, hBitmap, 0, bm.bmHeight, colorBits.get(), &bmi, DIB_RGB_COLORS);

	// Check whether the color bitmap has an alpha channel.
	BOOL hasAlpha = FALSE;
	for (int i = 0; i < nBits; i++) {
		if ((colorBits[i] & 0xff000000) != 0) {
			hasAlpha = TRUE;
			break;
		}
	}

	// If no alpha values available, apply the mask bitmap
	if (!hasAlpha) {
		// Extract the mask bitmap
		int32_t* maskBits = new int32_t[nBits];
		GetDIBits(dc, hMask, 0, bm.bmHeight, maskBits, &bmi, DIB_RGB_COLORS);
		// Copy the mask alphas into the color bits
		for (int i = 0; i < nBits; i++) {
			if (maskBits[i] == 0) {
				colorBits[i] |= 0xff000000;
			}
		}
		delete[] maskBits;
	}

	// Release DC and GDI bitmaps
	ReleaseDC(NULL, dc);
	DeleteObject(hBitmap);
	if (hMask != NULL)
		DeleteObject(hMask);


	{
		winrt::Microsoft::UI::Xaml::Media::Imaging::WriteableBitmap bitmap{ bm.bmWidth, bm.bmHeight };
		auto buffer = bitmap.PixelBuffer();