/*
	Jonathan?Dummer
	2007-07-31-10.32

	simple?DXT?compression?/?decompression?code

	public?domain
*/

#include?“image_DXT.h“
#include?
#include?
#include?
#include?

/*	set?this?=1?if?you?want?to?use?the?covarince?matrix?method...
	which?is?better?than?my?method?of?using?standard?deviations
	overall?except?on?the?infintesimal?chance?that?the?power
	method?fails?for?finding?the?largest?eigenvector	*/
#define?USE_COV_MAT	1

/*********?Function?Prototypes?*********/
/*
	Takes?a?4x4?block?of?pixels?and?compresses?it?into?8?bytes
	in?DXT1?format?（color?only?no?alpha）.??Speed?is?valued
	over?prettyness?at?least?for?now.
*/
void?compress_DDS_color_block（
				int?channels
				const?unsigned?char?*const?uncompressed
				unsigned?char?compressed[8]?）;
/*
	Takes?a?4x4?block?of?pixels?and?compresses?the?alpha
	component?it?into?8?bytes?for?use?in?DXT5?DDS?files.
	Speed?is?valued?over?prettyness?at?least?for?now.
*/
void?compress_DDS_alpha_block（
				const?unsigned?char?*const?uncompressed
				unsigned?char?compressed[8]?）;

/*********?Actual?Exposed?Functions?*********/
int
	save_image_as_DDS
	（
		const?char?*filename
		int?width?int?height?int?channels
		const?unsigned?char?*const?data
	）
{
	/*	variables	*/
	FILE?*fout;
	unsigned?char?*DDS_data;
	DDS_header?header;
	int?DDS_size;
	/*	error?check	*/
	if（?（NULL?==?filename）?||
		（width?		（channels??4）?||
		（data?==?NULL?）?）
	{
		return?0;
	}
	/*	Convert?the?image	*/
	if（?（channels?&?1）?==?1?）
	{
		/*	no?alpha?just?use?DXT1	*/
		DDS_data?=?convert_image_to_DXT1（?data?width?height?channels?&DDS_size?）;
	}?else
	{
		/*	has?alpha?so?use?DXT5	*/
		DDS_data?=?convert_image_to_DXT5（?data?width?height?channels?&DDS_size?）;
	}
	/*	save?it	*/
	memset（?&header?0?sizeof（?DDS_header?）?）;
	header.dwMagic?=?（‘D‘?<	header.dwSize?=?124;
	header.dwFlags?=?DDSD_CAPS?|?DDSD_HEIGHT?|?DDSD_WIDTH?|?DDSD_PIXELFORMAT?|?DDSD_LINEARSIZE;
	header.dwWidth?=?width;
	header.dwHeight?=?height;
	header.dwPitchOrLinearSize?=?DDS_size;
	header.sPixelFormat.dwSize?=?32;
	header.sPixelFormat.dwFlags?=?DDPF_FOURCC;
	if（?（channels?&?1）?==?1?）
	{
		header.sPixelFormat.dwFourCC?=?（‘D‘?<	}?else
	{
		header.sPixelFormat.dwFourCC?=?（‘D‘?<	}
	header.sCaps.dwCaps1?=?DDSCAPS_TEXTURE;
	/*	write?it?out	*/
	fout?=?fopen（?filename?“wb“）;
	fwrite（?&header?sizeof（?DDS_header?）?1?fout?）;
	fwrite（?DDS_data?1?DDS_size?fout?）;
	fclose（?fout?）;
	/*	done	*/
	free（?DDS_data?）;
	return?1;
}

unsigned?char*?convert_image_to_DXT1（
		const?unsigned?char?*const?uncompressed
		int?width?int?height?int?channels
		int?*out_size?）
{
	unsigned?char?*compressed;
	int?i?j?x?y;
	unsigned?char?ublock[16*3];
	unsigned?cha