Function IconToBitmap32

source/util.cpp:2722–2827

Lexikos: Used for menu icons on Windows Vista and later. Some similarities to IconToBitmap, maybe should be merged if IconToBitmap does not specifically need to create a device-dependent bitmap?

// Lexikos: Used for menu icons on Windows Vista and later. Some similarities to IconToBitmap, maybe should be merged if IconToBitmap does not specifically need to create a device-dependent bitmap?
HBITMAP IconToBitmap32(HICON ahIcon, bool aDestroyIcon)
{
	// Get the icon's internal colour and mask bitmaps.
	// hbmColor is needed to measure the icon.
	// hbmMask is needed to generate an alpha channel if the icon does not have one.
	ICONINFO icon_info;
	if (!GetIconInfo(ahIcon, &icon_info))
		return NULL;

	HBITMAP hbitmap = NULL; // Set default in case of failure.

	// Get size of icon's internal bitmap.
	BITMAP icon_bitmap;
	if (GetObject(icon_info.hbmColor, sizeof(BITMAP), &icon_bitmap))
	{
		int width = icon_bitmap.bmWidth;
		int height = icon_bitmap.bmHeight;

		HDC hdc = CreateCompatibleDC(NULL);
		if (hdc)
		{
			BITMAPINFO bitmap_info = {0};
			// Set parameters for 32-bit bitmap. May also be used to retrieve bitmap data from the icon's mask bitmap.
			BITMAPINFOHEADER &bitmap_header = bitmap_info.bmiHeader;
			bitmap_header.biSize = sizeof(BITMAPINFOHEADER);
			bitmap_header.biWidth = width;
			bitmap_header.biHeight = height;
			bitmap_header.biBitCount = 32;
			bitmap_header.biPlanes = 1;

			// Create device-independent bitmap.
			UINT *bits;
			if (hbitmap = CreateDIBSection(hdc, &bitmap_info, 0, (void**)&bits, NULL, 0))
			{
				HGDIOBJ old_object = SelectObject(hdc, hbitmap);
				if (old_object) // Above succeeded.
				{
					// Draw icon onto bitmap. Use DrawIconEx because DrawIcon always draws a large (usually 32x32) icon!
					DrawIconEx(hdc, 0, 0, ahIcon, 0, 0, 0, NULL, DI_NORMAL);

					// May be necessary for bits to be in sync, according to documentation for CreateDIBSection:
					GdiFlush();

					// Calculate end of bitmap data.
					UINT *bits_end = bits + width*height;
					
					UINT *this_pixel; // Used in a few loops below.

					// Check for alpha data.
					bool has_nonzero_alpha = false;
					for (this_pixel = bits; this_pixel < bits_end; ++this_pixel)
					{
						if (*this_pixel >> 24)
						{
							has_nonzero_alpha = true;
							break;
						}
					}