ddslib.cpp

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/* -----------------------------------------------------------------------------

DDS Library 

Based on code from Nvidia's DDS example:
http://www.nvidia.com/object/dxtc_decompression_code.html

Copyright (c) 2003 Randy Reddig
All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list
of conditions and the following disclaimer.

Redistributions in binary form must reproduce the above copyright notice, this
list of conditions and the following disclaimer in the documentation and/or
other materials provided with the distribution.

Neither the names of the copyright holders nor the names of its contributors may
be used to endorse or promote products derived from this software without
specific prior written permission. 

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Modified by: John Steele November 2005
----------------------------------------------------------------------------- */



/* marker */
#define DDSLIB_C

/* dependencies */
#include "ddslib.h"

/* endian tomfoolery */
typedef union
{
	float	f;
	char	c[ 4 ];
}
floatSwapUnion;

#ifndef __BIG_ENDIAN__
	#ifdef _SGI_SOURCE
		#define	__BIG_ENDIAN__
	#endif
#endif


#ifdef __BIG_ENDIAN__

	int   DDSBigLong( int src ) { return src; }
	short DDSBigShort( short src ) { return src; }
	float DDSBigFloat( float src ) { return src; }

	int DDSLittleLong( int src )
	{
		return ((src & 0xFF000000) >> 24) |
			   ((src & 0x00FF0000) >> 8) |
			   ((src & 0x0000FF00) << 8) |
			   ((src & 0x000000FF) << 24);
	}

	short DDSLittleShort( short src )
	{
		return ((src & 0xFF00) >> 8) |
			   ((src & 0x00FF) << 8);
	}

	float DDSLittleFloat( float src )
	{
		floatSwapUnion in,out;
		in.f = src;
		out.c[ 0 ] = in.c[ 3 ];
		out.c[ 1 ] = in.c[ 2 ];
		out.c[ 2 ] = in.c[ 1 ];
		out.c[ 3 ] = in.c[ 0 ];
		return out.f;
	}

#else /*__BIG_ENDIAN__*/

	int   DDSLittleLong( int src ) { return src; }
	short DDSLittleShort( short src ) { return src; }
	float DDSLittleFloat( float src ) { return src; }
		
	int DDSBigLong( int src )
	{
		return ((src & 0xFF000000) >> 24) |
			   ((src & 0x00FF0000) >> 8) |
			   ((src & 0x0000FF00) << 8) |
			   ((src & 0x000000FF) << 24);
	}
		
	short DDSBigShort( short src )
	{
		return ((src & 0xFF00) >> 8) |
			   ((src & 0x00FF) << 8);
	}
		
	float DDSBigFloat( float src )
	{
		floatSwapUnion in,out;
		in.f = src;
		out.c[ 0 ] = in.c[ 3 ];
		out.c[ 1 ] = in.c[ 2 ];
		out.c[ 2 ] = in.c[ 1 ];
		out.c[ 3 ] = in.c[ 0 ];
		return out.f;
	}

#endif /*__BIG_ENDIAN__*/



///*
//DDSDecodePixelFormat()
//determines which pixel format the dds texture is in
//*/
//
//static void DDSDecodePixelFormat( ddsBuffer_t *dds, ddsPF_t *pf )
//{
//	unsigned int	fourCC;
//	
//	
//	/* dummy check */
//	if(	dds == NULL || pf == NULL )
//		return;
//	
//	/* extract fourCC */
//	fourCC = dds->pixelFormat.fourCC;
//	
//	/* test it */
//	if( fourCC == 0 )
//		*pf = DDS_PF_ARGB8888;
//	else if( fourCC == *((unsigned int*) "DXT1") )
//		*pf = DDS_PF_DXT1;
//	else if( fourCC == *((unsigned int*) "DXT2") )
//		*pf = DDS_PF_DXT2;
//	else if( fourCC == *((unsigned int*) "DXT3") )
//		*pf = DDS_PF_DXT3;
//	else if( fourCC == *((unsigned int*) "DXT4") )
//		*pf = DDS_PF_DXT4;
//	else if( fourCC == *((unsigned int*) "DXT5") )
//		*pf = DDS_PF_DXT5;
//	else
//		*pf = DDS_PF_UNKNOWN;
//}
//
//
//
///*
//DDSGetInfo()
//extracts relevant info from a dds texture, returns 0 on success
//*/
//
//int DDSGetInfo( ddsBuffer_t *dds, int *width, int *height, ddsPF_t *pf )
//{
//	/* dummy test */
//	if( dds == NULL )
//		return -1;
//	
//	/* test dds header */
//	if( *((int*) dds->magic) != *((int*) "DDS ") )
//		return -1;
//	if( DDSLittleLong( dds->size ) != 124 )
//		return -1;
//	
//	/* extract width and height */
//	if( width != NULL )
//		*width = DDSLittleLong( dds->width );
//	if( height != NULL )
//		*height = DDSLittleLong( dds->height );
//	
//	/* get pixel format */
//	DDSDecodePixelFormat( dds, pf );
//	
//	/* return ok */
//	return 0;
//}



/*
DDSGetColorBlockColors()
extracts colors from a dds color block
*/

static void DDSGetColorBlockColors( ddsColorBlock_t *block, ddsColor_t colors[ 4 ] )
{
	unsigned short		word;

	
	/* color 0 */
	word = DDSLittleShort( block->colors[ 0 ] );
	colors[ 0 ].a = 0xff;
	
	/* extract rgb bits */
	colors[ 0 ].b = (unsigned char)(word & 0xFF);
	colors[ 0 ].b <<= 3;
	colors[ 0 ].b |= (colors[ 0 ].b >> 5);
	word >>= 5;
	colors[ 0 ].g = (unsigned char)(word & 0xFF);
	colors[ 0 ].g <<= 2;
	colors[ 0 ].g |= (colors[ 0 ].g >> 5);
	word >>= 6;
	colors[ 0 ].r = (unsigned char)(word & 0xFF);
	colors[ 0 ].r <<= 3;
	colors[ 0 ].r |= (colors[ 0 ].r >> 5);

	/* same for color 1 */
	word = DDSLittleShort( block->colors[ 1 ] );
	colors[ 1 ].a = 0xff;
	
	/* extract rgb bits */
	colors[ 1 ].b = (unsigned char)(word & 0xFF);
	colors[ 1 ].b <<= 3;
	colors[ 1 ].b |= (colors[ 1 ].b >> 5);
	word >>= 5;
	colors[ 1 ].g = (unsigned char)(word & 0xFF);
	colors[ 1 ].g <<= 2;
	colors[ 1 ].g |= (colors[ 1 ].g >> 5);
	word >>= 6;
	colors[ 1 ].r = (unsigned char)(word & 0xFF);
	colors[ 1 ].r <<= 3;
	colors[ 1 ].r |= (colors[ 1 ].r >> 5);
	
	/* use this for all but the super-freak math method */
	if( block->colors[ 0 ] > block->colors[ 1 ] )
	{
		/* four-color block: derive the other two colors.    
		   00 = color 0, 01 = color 1, 10 = color 2, 11 = color 3
		   these two bit codes correspond to the 2-bit fields 
		   stored in the 64-bit block. */

		word = ((unsigned short) colors[ 0 ].r * 2 + (unsigned short) colors[ 1 ].r ) / 3;
											/* no +1 for rounding */
											/* as bits have been shifted to 888 */
		colors[ 2 ].r = (unsigned char) word;
		word = ((unsigned short) colors[ 0 ].g * 2 + (unsigned short) colors[ 1 ].g) / 3;
		colors[ 2 ].g = (unsigned char) word;
		word = ((unsigned short) colors[ 0 ].b * 2 + (unsigned short) colors[ 1 ].b) / 3;
		colors[ 2 ].b = (unsigned char) word;
		colors[ 2 ].a = 0xff;

		word = ((unsigned short) colors[ 0 ].r + (unsigned short) colors[ 1 ].r * 2) / 3;
		colors[ 3 ].r = (unsigned char) word;
		word = ((unsigned short) colors[ 0 ].g + (unsigned short) colors[ 1 ].g * 2) / 3;
		colors[ 3 ].g = (unsigned char) word;
		word = ((unsigned short) colors[ 0 ].b + (unsigned short) colors[ 1 ].b * 2) / 3;
		colors[ 3 ].b = (unsigned char) word;
		colors[ 3 ].a = 0xff;
	} else {
		/* three-color block: derive the other color.
		   00 = color 0, 01 = color 1, 10 = color 2,  
		   11 = transparent.
		   These two bit codes correspond to the 2-bit fields 
		   stored in the 64-bit block */

		word = ((unsigned short) colors[ 0 ].r + (unsigned short) colors[ 1 ].r) / 2;
		colors[ 2 ].r = (unsigned char)(word & 0xFF);
		word = ((unsigned short) colors[ 0 ].g + (unsigned short) colors[ 1 ].g) / 2;
		colors[ 2 ].g = (unsigned char)(word & 0xFF);
		word = ((unsigned short) colors[ 0 ].b + (unsigned short) colors[ 1 ].b) / 2;
		colors[ 2 ].b = (unsigned char)(word & 0xFF);
		colors[ 2 ].a = 0xff;
		
		/* random color to indicate alpha */
		colors[ 3 ].r = 0x00;
		colors[ 3 ].g = 0xff;
		colors[ 3 ].b = 0xff;
		colors[ 3 ].a = 0x00;
	}
}



/*
DDSDecodeColorBlock()
decodes a dds color block
fixme: make endian-safe
*/

static void DDSDecodeColorBlock( unsigned int *pixel, ddsColorBlock_t *block, int width, unsigned int colors[ 4 ] )
{
	int				r, n;
	unsigned int	bits;
	unsigned int	masks[] = { 3, 12, 3 << 4, 3 << 6 };	/* bit masks = 00000011, 00001100, 00110000, 11000000 */
	int				shift[] = { 0, 2, 4, 6 };
	
	
	/* r steps through lines in y */
	for( r = 0; r < 4; r++, pixel += (width - 4) )	/* no width * 4 as unsigned int ptr inc will * 4 */
	{
		/* width * 4 bytes per pixel per line, each j dxtc row is 4 lines of pixels */

		/* n steps through pixels */
		for( n = 0; n < 4; n++ )
		{
			bits = block->row[ r ] & masks[ n ];
			bits >>= shift[ n ];

			switch( bits )
			{
				case 0:
					*pixel = colors[ 0 ];
					pixel++;
					break;

				case 1:
					*pixel = colors[ 1 ];
					pixel++;
					break;

				case 2:
					*pixel = colors[ 2 ];
					pixel++;
					break;

				case 3:
					*pixel = colors[ 3 ];
					pixel++;
					break;

				default:
					/* invalid */
					pixel++;
					break;
			}
		}
	}
}



/*
DDSDecodeAlphaExplicit()
decodes a dds explicit alpha block
*/

static void DDSDecodeAlphaExplicit( unsigned int *pixel, ddsAlphaBlockExplicit_t *alphaBlock, int width, unsigned int alphaZero )
{	
	int				row, pix;
	unsigned short	word;
	ddsColor_t		color;
	
	
	/* clear color */
	color.r = 0;
	color.g = 0;
	color.b = 0;
	
	/* walk rows */
	for( row = 0; row < 4; row++, pixel += (width - 4) )
	{
		word = DDSLittleShort( alphaBlock->row[ row ] );
		
		/* walk pixels */
		for( pix = 0; pix < 4; pix++ )
		{
			/* zero the alpha bits of image pixel */
			*pixel &= alphaZero;
			color.a = word & 0x000F;
			color.a = color.a | (color.a << 4);
			*pixel |= *((unsigned int*) &color);
			word >>= 4;		/* move next bits to lowest 4 */
			pixel++;		/* move to next pixel in the row */

		}
	}
}



/*
DDSDecodeAlpha3BitLinear()
decodes interpolated alpha block
*/