protected:
	unsigned m_alphas[8];
	unsigned m_alphaBits;
	int m_offset;

public:
	void Setup (const BYTE *pBlock) {
		base::Setup (pBlock);

		const DXTAlphaBlock3BitLinear &block = m_pBlock->alpha;
		m_alphas[0] = block.alpha[0];
		m_alphas[1] = block.alpha[1];
		if (m_alphas[0] > m_alphas[1]) {
			// 8 alpha block
			for (int i = 0; i < 6; i++) {
				m_alphas[i + 2] = ((6 - i) * m_alphas[0] + (1 + i) * m_alphas[1] + 3) / 7;
			}
		}
		else {
			// 6 alpha block
			for (int i = 0; i < 4; i++) {
				m_alphas[i + 2] = ((4 - i) * m_alphas[0] + (1 + i) * m_alphas[1] + 2) / 5;
			}
			m_alphas[6] = 0;
			m_alphas[7] = 0xFF;
		}

	}

	void SetY (int y) {
		base::SetY (y);
		int i = y / 2;
		const DXTAlphaBlock3BitLinear &block = m_pBlock->alpha;
		m_alphaBits = unsigned(block.data[0 + i * 3]) | (unsigned(block.data[1 + i * 3]) << 8)
			| (unsigned(block.data[2 + i * 3]) << 16);
		m_offset = (y & 1) * 12;
	}

	void GetColor (int x, int y, Color8888 &color) {
		base::GetColor (x, y, color);
		unsigned bits = (m_alphaBits >> (x * 3 + m_offset)) & 7;
		color.a = m_alphas[bits];
	}
};

template <class DECODER> void DecodeDXTBlock (BYTE *dstData, const BYTE *srcBlock, long dstPitch, int bw, int bh) {
	DECODER decoder;
	decoder.Setup (srcBlock);
	for (int y = 0; y < bh; y++) {
		BYTE *dst = dstData - y * dstPitch;
		decoder.SetY (y);
		for (int x = 0; x < bw; x++) {
			decoder.GetColor (x, y, (Color8888 &)*dst);
			dst += 4;
		}
	}
}

// ==========================================================
// Plugin Interface
// ==========================================================

static int s_format_id;

// ==========================================================
// Internal functions
// ==========================================================

static FIBITMAP *
LoadRGB (DDSURFACEDESC2 &desc, FreeImageIO *io, fi_handle handle, int page, int flags, void *data) {
	int width = (int)desc.dwWidth;
	int height = (int)desc.dwHeight;
	int bpp = (int)desc.ddpfPixelFormat.dwRGBBitCount;
	
	// allocate a new dib
	FIBITMAP *dib = FreeImage_Allocate (width, height, bpp, desc.ddpfPixelFormat.dwRBitMask,
		desc.ddpfPixelFormat.dwGBitMask, desc.ddpfPixelFormat.dwBBitMask);
	if (dib == NULL)
		return NULL;

#ifdef FREEIMAGE_BIGENDIAN
		// Calculate the number of bytes per pixel (3 for 24-bit or 4 for 32-bit)
		int bytespp = FreeImage_GetLine(dib) / FreeImage_GetWidth(dib);
#endif
	
	// read the file
	int line   = CalculateLine(width, bpp);
	int filePitch = (desc.dwFlags & DDSD_PITCH) ? (int)desc.dwPitchOrLinearSize : line;
	long delta = (long)filePitch - (long)line;
	for (int i = 0; i < height; i++) {
		BYTE *pixels = FreeImage_GetScanLine(dib, height - i - 1);
		io->read_proc (pixels, 1, line, handle);
		io->seek_proc (handle, delta, SEEK_CUR);
#ifdef FREEIMAGE_BIGENDIAN
 		for(int x = 0; x < width; x++) {
			INPLACESWAP(pixels[FI_RGBA_RED],pixels[FI_RGBA_BLUE]);
			pixels += bytespp;
		}
#endif
	}
	
	// enable transparency
	FreeImage_SetTransparent (dib, (desc.ddpfPixelFormat.dwFlags & DDPF_ALPHAPIXELS) ? TRUE : FALSE);

	if (!(desc.ddpfPixelFormat.dwFlags & DDPF_ALPHAPIXELS) && bpp == 32) {
		// no transparency: convert to 24-bit
		FIBITMAP *old = dib;
		dib = FreeImage_ConvertTo24Bits (old);
		FreeImage_Unload (old);
	}
	return dib;
}

template <class DECODER> static void 
LoadDXT_Helper (FreeImageIO *io, fi_handle handle, int page, int flags, void *data, FIBITMAP *dib, BYTE *bits, int width, int height, int line) {
	typedef typename DECODER::INFO INFO;
	typedef typename INFO::Block Block;

	Block *input_buffer = new Block[(width + 3) / 4];
	int widthFullBlocks = width / 4;
	int heightFullBlocks = height / 4;
	int widthRest = (int) width & 3;
	int heightRest = (int) height & 3;
	int inputLine = (width + 3) / 4;
	int y = 0;

	if (height >= 4) {
		for (; y < height; y += 4) {
			io->read_proc (input_buffer, sizeof (typename INFO::Block), inputLine, handle);
			// TODO: probably need some endian work here
			BYTE *pbSrc = (BYTE *)input_buffer;
			BYTE *pbDst = FreeImage_GetScanLine (dib, height - y - 1);

			if (width >= 4) {
				for (int x = 0; x < width; x += 4) {
					DecodeDXTBlock <DECODER> (pbDst, pbSrc,	line, 4, 4);
					pbSrc += INFO::bytesPerBlock;
					pbDst += 4 * 4;
				}
			}
			if (widthRest) {
				DecodeDXTBlock <DECODER> (pbDst, pbSrc, line, widthRest, 4);
			}
		}
	}
	if (heightRest)	{
		io->read_proc (input_buffer, sizeof (typename INFO::Block), inputLine, handle);
		// TODO: probably need some endian work here
		BYTE *pbSrc = (BYTE *)input_buffer;
		BYTE *pbDst = FreeImage_GetScanLine (dib, height - y - 1);

		if (width >= 4) {
			for (int x = 0; x < width; x += 4) {
				DecodeDXTBlock <DECODER> (pbDst, pbSrc,	line, 4, heightRest);
				pbSrc += INFO::bytesPerBlock;
				pbDst += 4 * 4;
			}
		}
		if (widthRest) {
			DecodeDXTBlock <DECODER> (pbDst, pbSrc,	line, widthRest, heightRest);
		}

	}
}

static FIBITMAP *
LoadDXT (int type, DDSURFACEDESC2 &desc, FreeImageIO *io, fi_handle handle, int page, int flags, void *data) {
	int width = (int)desc.dwWidth;
	int height = (int)desc.dwHeight;

	// allocate a 32-bit dib
	FIBITMAP *dib = FreeImage_Allocate (width, height, 32, FI_RGBA_RED_MASK, FI_RGBA_GREEN_MASK, FI_RGBA_BLUE_MASK);
	if (dib == NULL)
		return NULL;

	int bpp = FreeImage_GetBPP (dib);
	int line = CalculateLine (width, bpp);
	BYTE *bits = FreeImage_GetBits (dib);

	// select the right decoder
	switch (type) {
		case 1:
			LoadDXT_Helper <DXT_BLOCKDECODER_1> (io, handle, page, flags, data, dib, bits, width, height, line);
			break;
		case 3:
			LoadDXT_Helper <DXT_BLOCKDECODER_3> (io, handle, page, flags, data, dib, bits, width, height, line);
			break;
		case 5:
			LoadDXT_Helper <DXT_BLOCKDECODER_5> (io, handle, page, flags, data, dib, bits, width, height, line);
			break;
	}
	
	return dib;
}
// ==========================================================
// Plugin Implementation
// ==========================================================

static const char * DLL_CALLCONV
Format() {
	return "DDS";
}

static const char * DLL_CALLCONV
Description() {
	return "DirectX Surface";
}

static const char * DLL_CALLCONV
Extension() {
	return "dds";
}

static const char * DLL_CALLCONV
RegExpr() {
	return NULL;
}

static const char * DLL_CALLCONV
MimeType() {
	return "image/freeimage-dds";
}

static BOOL DLL_CALLCONV
Validate(FreeImageIO *io, fi_handle handle) {
	DDSHEADER header;
	io->read_proc(&header, 1, sizeof(header), handle);
#ifdef FREEIMAGE_BIGENDIAN
	SwapHeader(&header);
#endif
	if (header.dwMagic != MAKEFOURCC ('D','D','S',' '))
		return FALSE;
	if (header.surfaceDesc.dwSize != sizeof (header.surfaceDesc) ||
		header.surfaceDesc.ddpfPixelFormat.dwSize != sizeof (header.surfaceDesc.ddpfPixelFormat))
		return FALSE;
	return TRUE;
}

static BOOL DLL_CALLCONV
SupportsExportDepth(int depth) {
	return FALSE;
}

static BOOL DLL_CALLCONV 
SupportsExportType(FREE_IMAGE_TYPE type) {
	return (type == FIT_BITMAP) ? TRUE : FALSE;
}

// ----------------------------------------------------------

static void * DLL_CALLCONV
Open(FreeImageIO *io, fi_handle handle, BOOL read) {
	return NULL;
}

static void DLL_CALLCONV
Close(FreeImageIO *io, fi_handle handle, void *data) {
}

// ----------------------------------------------------------

static FIBITMAP * DLL_CALLCONV
Load(FreeImageIO *io, fi_handle handle, int page, int flags, void *data) {
	DDSHEADER header;
	FIBITMAP *dib = NULL;
	io->read_proc(&header, 1, sizeof(header), handle);
#ifdef FREEIMAGE_BIGENDIAN
	SwapHeader(&header);
#endif
	if (header.surfaceDesc.ddpfPixelFormat.dwFlags & DDPF_RGB) {
		dib = LoadRGB (header.surfaceDesc, io, handle, page, flags, data);
	}
	else if (header.surfaceDesc.ddpfPixelFormat.dwFlags & DDPF_FOURCC) {
		switch (header.surfaceDesc.ddpfPixelFormat.dwFourCC) {
			case FOURCC_DXT1:
				dib = LoadDXT (1, header.surfaceDesc, io, handle, page, flags, data);
				break;
			case FOURCC_DXT3:
				dib = LoadDXT (3, header.surfaceDesc, io, handle, page, flags, data);
				break;
			case FOURCC_DXT5:
				dib = LoadDXT (5, header.surfaceDesc, io, handle, page, flags, data);
				break;
		}
	}
	return dib;
}

static BOOL DLL_CALLCONV
Save(FreeImageIO *io, FIBITMAP *dib, fi_handle handle, int page, int flags, void *data) {
	return FALSE;
}

// ==========================================================
//   Init
// ==========================================================

void DLL_CALLCONV
InitDDS(Plugin *plugin, int format_id) {
	s_format_id = format_id;

	plugin->format_proc = Format;
	plugin->description_proc = Description;
	plugin->extension_proc = Extension;
	plugin->regexpr_proc = RegExpr;
	plugin->open_proc = Open;
	plugin->close_proc = Close;
	plugin->pagecount_proc = NULL;
	plugin->pagecapability_proc = NULL;
	plugin->load_proc = Load;
	plugin->save_proc = NULL;	//Save;	// not implemented (yet?)
	plugin->validate_proc = Validate;
	plugin->mime_proc = MimeType;
	plugin->supports_export_bpp_proc = SupportsExportDepth;
	plugin->supports_export_type_proc = SupportsExportType;
	plugin->supports_icc_profiles_proc = NULL;
}