Drawing AA Text to a DIBitmap

[jamesleighe]

So, the idea is I'm trying to draw anti-aliased text to a DIB so that I can bitcopy that onto a texture for use as a bitmap-font.

Here is some code:

	// create a GDI font
	HFONT fontHandle = CreateFontA (
		size,					// height
		0,					// width
		0,					// escapement
		0,					// orientation
		FW_NORMAL,				// weight
		FALSE,					// italic
		FALSE,					// underline
		FALSE,					// strikeout
		ANSI_CHARSET,				// char set
		OUT_OUTLINE_PRECIS,			// out precision
		CLIP_DEFAULT_PRECIS,			// clip precision
		ANTIALIASED_QUALITY,			// quality
		VARIABLE_PITCH || FF_DONTCARE,		// pitch and family
		data_->face.CString ());		// face name

	HDC deviceContext = CreateCompatibleDC (NULL);
	if (!deviceContext)
		assert (0);

	// create a bitmap to render individual glyphs to
	BITMAPINFO bitmapInfo;
	memset (&bitmapInfo, 0, sizeof (bitmapInfo));
	bitmapInfo.bmiHeader.biSize = sizeof (BITMAPINFOHEADER);
	bitmapInfo.bmiHeader.biWidth = glyphSize;
	// negative height to store bitmatp data in raster scan order
	bitmapInfo.bmiHeader.biHeight = -glyphSize;
	bitmapInfo.bmiHeader.biPlanes = 1;
	bitmapInfo.bmiHeader.biBitCount = 32;

	void* bitmapMemoryBase;
	HBITMAP bitmap = CreateDIBSection (NULL, &bitmapInfo, DIB_RGB_COLORS, &bitmapMemoryBase, NULL, NULL);
	if (!bitmap)
		assert (0);

	// select in objects & setup for rendering
	SelectObject (deviceContext, fontHandle);
	SelectObject (deviceContext, bitmap);
	SetTextColor (deviceContext, RGB (255, 255, 255));
	SetBkColor (deviceContext, RGB (0, 0, 0));
	SetBkMode (deviceContext, OPAQUE);


(some time later)
	if (DrawTextA (deviceContext, (LPCSTR)stringBuf.CString (), 1, &rect, DT_LEFT | DT_SINGLELINE | DT_NOCLIP) == 0)
			assert (0);

Using this method the text comes out without anti-aliasing.

I found that I can get AA to work if I use the "SCREEN" dc and a DDB instead of a DIB but that renders visibly to the screen...

Any ideas?

[ahmd]

My guess would be that you somehow lose the alpha-channel information for your DIB section. In most cases GDI functions can only process the RGB data, when anti-aliasing deals with RGBA or ARGB (meaning that there's also a byte for an alpha channel). Since your code sample above doesn't show how you deal with bitmapMemoryBase my guess would be that...