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///	DDS file support, does decoding, _not_ direct uploading

///	(use SOIL for that ;-)

///	A bunch of DirectDraw Surface structures and flags

typedef struct {

    unsigned int    dwMagic;

    unsigned int    dwSize;

    unsigned int    dwFlags;

    unsigned int    dwHeight;

    unsigned int    dwWidth;

    unsigned int    dwPitchOrLinearSize;

    unsigned int    dwDepth;

    unsigned int    dwMipMapCount;

    unsigned int    dwReserved1[ 11 ];

    //  DDPIXELFORMAT

    struct {

      unsigned int    dwSize;

      unsigned int    dwFlags;

      unsigned int    dwFourCC;

      unsigned int    dwRGBBitCount;

      unsigned int    dwRBitMask;

      unsigned int    dwGBitMask;

      unsigned int    dwBBitMask;

      unsigned int    dwAlphaBitMask;

    }               sPixelFormat;

    //  DDCAPS2

    struct {

      unsigned int    dwCaps1;

      unsigned int    dwCaps2;

      unsigned int    dwDDSX;

      unsigned int    dwReserved;

    }               sCaps;

    unsigned int    dwReserved2;

} DDS_header ;

//	the following constants were copied directly off the MSDN website

//	The dwFlags member of the original DDSURFACEDESC2 structure

//	can be set to one or more of the following values.

#define DDSD_CAPS	0x00000001

#define DDSD_HEIGHT	0x00000002

#define DDSD_WIDTH	0x00000004

#define DDSD_PITCH	0x00000008

#define DDSD_PIXELFORMAT	0x00001000

#define DDSD_MIPMAPCOUNT	0x00020000

#define DDSD_LINEARSIZE	0x00080000

#define DDSD_DEPTH	0x00800000

//	DirectDraw Pixel Format

#define DDPF_ALPHAPIXELS	0x00000001

#define DDPF_FOURCC	0x00000004

#define DDPF_RGB	0x00000040

//	The dwCaps1 member of the DDSCAPS2 structure can be

//	set to one or more of the following values.

#define DDSCAPS_COMPLEX	0x00000008

#define DDSCAPS_TEXTURE	0x00001000

#define DDSCAPS_MIPMAP	0x00400000

//	The dwCaps2 member of the DDSCAPS2 structure can be

//	set to one or more of the following values.

#define DDSCAPS2_CUBEMAP	0x00000200

#define DDSCAPS2_CUBEMAP_POSITIVEX	0x00000400

#define DDSCAPS2_CUBEMAP_NEGATIVEX	0x00000800

#define DDSCAPS2_CUBEMAP_POSITIVEY	0x00001000

#define DDSCAPS2_CUBEMAP_NEGATIVEY	0x00002000

#define DDSCAPS2_CUBEMAP_POSITIVEZ	0x00004000

#define DDSCAPS2_CUBEMAP_NEGATIVEZ	0x00008000

#define DDSCAPS2_VOLUME	0x00200000

static int dds_test(stbi *s)

{

	//	check the magic number

	if (get8(s) != 'D') return 0;

	if (get8(s) != 'D') return 0;

	if (get8(s) != 'S') return 0;

	if (get8(s) != ' ') return 0;

	//	check header size

	if (get32le(s) != 124) return 0;

	return 1;

}

#ifndef STBI_NO_STDIO

int      stbi_dds_test_file        (FILE *f)

{

   stbi s;

   int r,n = ftell(f);

   start_file(&s,f);

   r = dds_test(&s);

   fseek(f,n,SEEK_SET);

   return r;

}

#endif

int      stbi_dds_test_memory      (stbi_uc const *buffer, int len)

{

   stbi s;

   start_mem(&s,buffer, len);

   return dds_test(&s);

}

//	helper functions

int stbi_convert_bit_range( int c, int from_bits, int to_bits )

{

	int b = (1 << (from_bits - 1)) + c * ((1 << to_bits) - 1);

	return (b + (b >> from_bits)) >> from_bits;

}

void stbi_rgb_888_from_565( unsigned int c, int *r, int *g, int *b )

{

	*r = stbi_convert_bit_range( (c >> 11) & 31, 5, 8 );

	*g = stbi_convert_bit_range( (c >> 05) & 63, 6, 8 );

	*b = stbi_convert_bit_range( (c >> 00) & 31, 5, 8 );

}

void stbi_decode_DXT1_block(

			unsigned char uncompressed[16*4],

			unsigned char compressed[8] )

{

	int next_bit = 4*8;

	int i, r, g, b;

	int c0, c1;

	unsigned char decode_colors[4*4];

	//	find the 2 primary colors

	c0 = compressed[0] + (compressed[1] << 8);

	c1 = compressed[2] + (compressed[3] << 8);

	stbi_rgb_888_from_565( c0, &r, &g, &b );

	decode_colors[0] = r;

	decode_colors[1] = g;

	decode_colors[2] = b;

	decode_colors[3] = 255;

	stbi_rgb_888_from_565( c1, &r, &g, &b );

	decode_colors[4] = r;

	decode_colors[5] = g;

	decode_colors[6] = b;

	decode_colors[7] = 255;

	if( c0 > c1 )

	{

		//	no alpha, 2 interpolated colors

		decode_colors[8] = (2*decode_colors[0] + decode_colors[4]) / 3;

		decode_colors[9] = (2*decode_colors[1] + decode_colors[5]) / 3;

		decode_colors[10] = (2*decode_colors[2] + decode_colors[6]) / 3;

		decode_colors[11] = 255;

		decode_colors[12] = (decode_colors[0] + 2*decode_colors[4]) / 3;

		decode_colors[13] = (decode_colors[1] + 2*decode_colors[5]) / 3;

		decode_colors[14] = (decode_colors[2] + 2*decode_colors[6]) / 3;

		decode_colors[15] = 255;

	} else

	{

		//	1 interpolated color, alpha

		decode_colors[8] = (decode_colors[0] + decode_colors[4]) / 2;

		decode_colors[9] = (decode_colors[1] + decode_colors[5]) / 2;

		decode_colors[10] = (decode_colors[2] + decode_colors[6]) / 2;

		decode_colors[11] = 255;

		decode_colors[12] = 0;

		decode_colors[13] = 0;

		decode_colors[14] = 0;

		decode_colors[15] = 0;

	}

	//	decode the block

	for( i = 0; i < 16*4; i += 4 )

	{

		int idx = ((compressed[next_bit>>3] >> (next_bit & 7)) & 3) * 4;

		next_bit += 2;

		uncompressed[i+0] = decode_colors[idx+0];

		uncompressed[i+1] = decode_colors[idx+1];

		uncompressed[i+2] = decode_colors[idx+2];

		uncompressed[i+3] = decode_colors[idx+3];

	}

	//	done

}

void stbi_decode_DXT23_alpha_block(

			unsigned char uncompressed[16*4],

			unsigned char compressed[8] )

{

	int i, next_bit = 0;

	//	each alpha value gets 4 bits

	for( i = 3; i < 16*4; i += 4 )

	{

		uncompressed[i] = stbi_convert_bit_range(

				(compressed[next_bit>>3] >> (next_bit&7)) & 15,

				4, 8 );

		next_bit += 4;

	}

}

void stbi_decode_DXT45_alpha_block(

			unsigned char uncompressed[16*4],

			unsigned char compressed[8] )

{

	int i, next_bit = 8*2;

	unsigned char decode_alpha[8];

	//	each alpha value gets 3 bits, and the 1st 2 bytes are the range

	decode_alpha[0] = compressed[0];

	decode_alpha[1] = compressed[1];

	if( decode_alpha[0] > decode_alpha[1] )

	{

		//	6 step intermediate

		decode_alpha[2] = (6*decode_alpha[0] + 1*decode_alpha[1]) / 7;

		decode_alpha[3] = (5*decode_alpha[0] + 2*decode_alpha[1]) / 7;

		decode_alpha[4] = (4*decode_alpha[0] + 3*decode_alpha[1]) / 7;

		decode_alpha[5] = (3*decode_alpha[0] + 4*decode_alpha[1]) / 7;

		decode_alpha[6] = (2*decode_alpha[0] + 5*decode_alpha[1]) / 7;

		decode_alpha[7] = (1*decode_alpha[0] + 6*decode_alpha[1]) / 7;

	} else

	{

		//	4 step intermediate, pluss full and none

		decode_alpha[2] = (4*decode_alpha[0] + 1*decode_alpha[1]) / 5;

		decode_alpha[3] = (3*decode_alpha[0] + 2*decode_alpha[1]) / 5;

		decode_alpha[4] = (2*decode_alpha[0] + 3*decode_alpha[1]) / 5;

		decode_alpha[5] = (1*decode_alpha[0] + 4*decode_alpha[1]) / 5;

		decode_alpha[6] = 0;

		decode_alpha[7] = 255;

	}

	for( i = 3; i < 16*4; i += 4 )

	{

		int idx = 0, bit;

		bit = (compressed[next_bit>>3] >> (next_bit&7)) & 1;

		idx += bit << 0;

		++next_bit;

		bit = (compressed[next_bit>>3] >> (next_bit&7)) & 1;

		idx += bit << 1;

		++next_bit;

		bit = (compressed[next_bit>>3] >> (next_bit&7)) & 1;

		idx += bit << 2;

		++next_bit;

		uncompressed[i] = decode_alpha[idx & 7];

	}

	//	done

}

void stbi_decode_DXT_color_block(

			unsigned char uncompressed[16*4],

			unsigned char compressed[8] )

{

	int next_bit = 4*8;

	int i, r, g, b;

	int c0, c1;

	unsigned char decode_colors[4*3];

	//	find the 2 primary colors

	c0 = compressed[0] + (compressed[1] << 8);

	c1 = compressed[2] + (compressed[3] << 8);

	stbi_rgb_888_from_565( c0, &r, &g, &b );

	decode_colors[0] = r;

	decode_colors[1] = g;

	decode_colors[2] = b;

	stbi_rgb_888_from_565( c1, &r, &g, &b );

	decode_colors[3] = r;

	decode_colors[4] = g;

	decode_colors[5] = b;

	//	Like DXT1, but no choicees:

	//	no alpha, 2 interpolated colors

	decode_colors[6] = (2*decode_colors[0] + decode_colors[3]) / 3;

	decode_colors[7] = (2*decode_colors[1] + decode_colors[4]) / 3;

	decode_colors[8] = (2*decode_colors[2] + decode_colors[5]) / 3;

	decode_colors[9] = (decode_colors[0] + 2*decode_colors[3]) / 3;

	decode_colors[10] = (decode_colors[1] + 2*decode_colors[4]) / 3;

	decode_colors[11] = (decode_colors[2] + 2*decode_colors[5]) / 3;

	//	decode the block

	for( i = 0; i < 16*4; i += 4 )

	{

		int idx = ((compressed[next_bit>>3] >> (next_bit & 7)) & 3) * 3;

		next_bit += 2;

		uncompressed[i+0] = decode_colors[idx+0];

		uncompressed[i+1] = decode_colors[idx+1];

		uncompressed[i+2] = decode_colors[idx+2];

	}

	//	done

}

static stbi_uc *dds_load(stbi *s, int *x, int *y, int *comp, int req_comp)

{

	//	all variables go up front

	stbi_uc *dds_data = NULL;

	stbi_uc block[16*4];

	stbi_uc compressed[8];

	int flags, DXT_family;

	int has_alpha, has_mipmap;

	int is_compressed, cubemap_faces;

	int block_pitch, num_blocks;

	DDS_header header;

	int i, sz, cf;

	//	load the header

	if( sizeof( DDS_header ) != 128 )

	{

		return NULL;

	}

	getn( s, (stbi_uc*)(&header), 128 );

	//	and do some checking

	if( header.dwMagic != (('D' << 0) | ('D' << 8) | ('S' << 16) | (' ' << 24)) ) return NULL;

	if( header.dwSize != 124 ) return NULL;

	flags = DDSD_CAPS | DDSD_HEIGHT | DDSD_WIDTH | DDSD_PIXELFORMAT;

	if( (header.dwFlags & flags) != flags ) return NULL;

	/*	According to the MSDN spec, the dwFlags should contain

		DDSD_LINEARSIZE if it's compressed, or DDSD_PITCH if

		uncompressed.  Some DDS writers do not conform to the

		spec, so I need to make my reader more tolerant	*/

	if( header.sPixelFormat.dwSize != 32 ) return NULL;

	flags = DDPF_FOURCC | DDPF_RGB;

	if( (header.sPixelFormat.dwFlags & flags) == 0 ) return NULL;

	if( (header.sCaps.dwCaps1 & DDSCAPS_TEXTURE) == 0 ) return NULL;

	//	get the image data

	s->img_x = header.dwWidth;

	s->img_y = header.dwHeight;

	s->img_n = 4;

	is_compressed = (header.sPixelFormat.dwFlags & DDPF_FOURCC) / DDPF_FOURCC;

	has_alpha = (header.sPixelFormat.dwFlags & DDPF_ALPHAPIXELS) / DDPF_ALPHAPIXELS;

	has_mipmap = (header.sCaps.dwCaps1 & DDSCAPS_MIPMAP) && (header.dwMipMapCount > 1);

	cubemap_faces = (header.sCaps.dwCaps2 & DDSCAPS2_CUBEMAP) / DDSCAPS2_CUBEMAP;

	/*	I need cubemaps to have square faces	*/

	cubemap_faces &= (s->img_x == s->img_y);

	cubemap_faces *= 5;

	cubemap_faces += 1;

	block_pitch = (s->img_x+3) >> 2;

	num_blocks = block_pitch * ((s->img_y+3) >> 2);

	/*	let the user know what's going on	*/

	*x = s->img_x;

	*y = s->img_y;

	*comp = s->img_n;

	/*	is this uncompressed?	*/

	if( is_compressed )

	{

		/*	compressed	*/

		//	note: header.sPixelFormat.dwFourCC is something like (('D'<<0)|('X'<<8)|('T'<<16)|('1'<<24))

		DXT_family = 1 + (header.sPixelFormat.dwFourCC >> 24) - '1';

		if( (DXT_family < 1) || (DXT_family > 5) ) return NULL;

		/*	check the expected size...oops, nevermind...

			those non-compliant writers leave

			dwPitchOrLinearSize == 0	*/

		//	passed all the tests, get the RAM for decoding

		sz = (s->img_x)*(s->img_y)*4*cubemap_faces;

		dds_data = (unsigned char*)malloc( sz );

		/*	do this once for each face	*/

		for( cf = 0; cf < cubemap_faces; ++ cf )

		{

			//	now read and decode all the blocks

			for( i = 0; i < num_blocks; ++i )

			{

				//	where are we?

				int bx, by, bw=4, bh=4;

				int ref_x = 4 * (i % block_pitch);

				int ref_y = 4 * (i / block_pitch);

				//	get the next block's worth of compressed data, and decompress it

				if( DXT_family == 1 )

				{

					//	DXT1

					getn( s, compressed, 8 );

					stbi_decode_DXT1_block( block, compressed );

				} else if( DXT_family < 4 )

				{

					//	DXT2/3

					getn( s, compressed, 8 );

					stbi_decode_DXT23_alpha_block ( block, compressed );

					getn( s, compressed, 8 );

					stbi_decode_DXT_color_block ( block, compressed );

				} else

				{

					//	DXT4/5

					getn( s, compressed, 8 );

					stbi_decode_DXT45_alpha_block ( block, compressed );

					getn( s, compressed, 8 );

					stbi_decode_DXT_color_block ( block, compressed );

				}

				//	is this a partial block?

				if( ref_x + 4 > s->img_x )

				{

					bw = s->img_x - ref_x;

				}

				if( ref_y + 4 > s->img_y )

				{

					bh = s->img_y - ref_y;

				}

				//	now drop our decompressed data into the buffer

				for( by = 0; by < bh; ++by )

				{

					int idx = 4*((ref_y+by+cf*s->img_x)*s->img_x + ref_x);

					for( bx = 0; bx < bw*4; ++bx )

					{

						dds_data[idx+bx] = block[by*16+bx];

					}

				}

			}

			/*	done reading and decoding the main image...

				skip MIPmaps if present	*/

			if( has_mipmap )

			{

				int block_size = 16;

				if( DXT_family == 1 )

				{

					block_size = 8;

				}

				for( i = 1; i < header.dwMipMapCount; ++i )

				{

					int mx = s->img_x >> (i + 2);

					int my = s->img_y >> (i + 2);

					if( mx < 1 )

					{

						mx = 1;

					}

					if( my < 1 )

					{

						my = 1;

					}

					skip( s, mx*my*block_size );

				}

			}

		}/* per cubemap face */

	} else

	{

		/*	uncompressed	*/

		DXT_family = 0;

		s->img_n = 3;

		if( has_alpha )

		{

			s->img_n = 4;

		}

		*comp = s->img_n;

		sz = s->img_x*s->img_y*s->img_n*cubemap_faces;

		dds_data = (unsigned char*)malloc( sz );

		/*	do this once for each face	*/

		for( cf = 0; cf < cubemap_faces; ++ cf )

		{

			/*	read the main image for this face	*/

			getn( s, &dds_data[cf*s->img_x*s->img_y*s->img_n], s->img_x*s->img_y*s->img_n );

			/*	done reading and decoding the main image...

				skip MIPmaps if present	*/

			if( has_mipmap )

			{

				for( i = 1; i < header.dwMipMapCount; ++i )

				{

					int mx = s->img_x >> i;

					int my = s->img_y >> i;

					if( mx < 1 )

					{

						mx = 1;

					}

					if( my < 1 )

					{

						my = 1;

					}

					skip( s, mx*my*s->img_n );

				}

			}

		}

		/*	data was BGR, I need it RGB	*/

		for( i = 0; i < sz; i += s->img_n )

		{

			unsigned char temp = dds_data[i];

			dds_data[i] = dds_data[i+2];

			dds_data[i+2] = temp;

		}

	}

	/*	finished decompressing into RGBA,

		adjust the y size if we have a cubemap

		note: sz is already up to date	*/

	s->img_y *= cubemap_faces;

	*y = s->img_y;

	//	did the user want something else, or

	//	see if all the alpha values are 255 (i.e. no transparency)

	has_alpha = 0;

	if( s->img_n == 4)

	{

		for( i = 3; (i < sz) && (has_alpha == 0); i += 4 )

		{

			has_alpha |= (dds_data[i] < 255);

		}

	}

	if( (req_comp <= 4) && (req_comp >= 1) )

	{

		//	user has some requirements, meet them

		if( req_comp != s->img_n )

		{

			dds_data = convert_format( dds_data, s->img_n, req_comp, s->img_x, s->img_y );

			*comp = s->img_n;

		}

	} else

	{

		//	user had no requirements, only drop to RGB is no alpha

		if( (has_alpha == 0) && (s->img_n == 4) )

		{

			dds_data = convert_format( dds_data, 4, 3, s->img_x, s->img_y );

			*comp = 3;

		}

	}

	//	OK, done

	return dds_data;

}

#ifndef STBI_NO_STDIO

stbi_uc *stbi_dds_load_from_file   (FILE *f,                  int *x, int *y, int *comp, int req_comp)

{

	stbi s;

   start_file(&s,f);

   return dds_load(&s,x,y,comp,req_comp);

}

stbi_uc *stbi_dds_load             (char *filename,           int *x, int *y, int *comp, int req_comp)

{

   stbi_uc *data;

   FILE *f = fopen(filename, "rb");

   if (!f) return NULL;

   data = stbi_dds_load_from_file(f,x,y,comp,req_comp);

   fclose(f);

   return data;

}

#endif

stbi_uc *stbi_dds_load_from_memory (stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)

{

	stbi s;

   start_mem(&s,buffer, len);

   return dds_load(&s,x,y,comp,req_comp);

}