#include "readloop-cvt.h"

double cvt_Kr;
double cvt_Kb;
int cvt_clip_Y;
int cvt_clip_CbCr;

//static unsigned short int to_rgb[3][3];

/*
 * In analog terms,
 *
 *	Y' = Kr R' + (1 - Kr - Kb) G' + Kb B'
 *	Pr = .5 (R' - Y') / (1 - Kr)
 *	Pb = .5 (B' - Y') / (1 - Kb)
 *
 * Expanding this to create the matrix form, we get, successively,
 *
 *	Y' = Kr R' + (1-Kr-Kb) G' + Kb B'
 *	Pr = .5 (R' - (Kr R' + (1-Kr-Kb) G' + Kb B')) / (1-Kr)
 *	Pb = .5 (B' - (Kr R' + (1-Kr-Kb) G' + Kb B')) / (1-Kb)
 *
 *	Y' = Kr R' + (1-Kr-Kb) G' + Kb B'
 *	Pr = .5 (R' - Kr R' - (1-Kr-Kb) G' - Kb B') / (1-Kr)
 *	Pb = .5 (B' - Kr R' - (1-Kr-Kb) G' - Kb B') / (1-Kb)
 *
 *	Y' = Kr R' + (1-Kr-Kb) G' + Kb B'
 *	Pr = ˝ R' - ˝(1-Kr-Kb)/(1-Kr) G' - ˝Kb/(1-Kr) B'
 *	Pb = - ˝Kr/(1-Kb) R' - ˝(1-Kr-Kb)/(1-Kb) G' + ˝ B'
 *
 *	[ Y' ]   [  Kr         1-Kr-Kb             Kb         ] [ R' ]
 *	[ Pr ] = [  ˝          -˝(1-Kr-Kb)/(1-Kr) -˝Kb/(1-Kr) ] [ G' ]
 *	[ Pb ]   [ -˝Kr/(1-Kb) -˝(1-Kr-Kb)/(1-Kb)  ˝          ] [ B' ]
 *
 * Because R'/G'/B' and Y'/Pr/Pb use the same scale (a range of 1,
 *  [0,1] for Y'/R'/G'/B' and [-˝,˝] for Pr/Pb) exactly the same matrix
 *  works for [0..255] Y'/R'/G'/B' and [-128..127] Cr/Cb.  When
 *  limited-range clipping is turned on, we have to adjust for it.
 *
 * In any case, the above is the wrong matrix, because it's to go
 *  _from_ RGB triples, not _to_ RGB triples.  We have to invert it.
 */

static void reset_cvt(void)
{
 double Kg;

 Kg = 1 - cvt_Kr - cvt_Kb;
}

void init_cvt(void)
{
 cvt_Kr = .299;
 cvt_Kb = .114;
 cvt_clip_Y = 0;
 cvt_clip_CbCr = 0;
 reset_cvt();
}