tif_luv.c

一个国人自己实现图像库的程序（有参考价值）

	for (shft = 4*8; (shft -= 8) >= 0; )
		for (i = 0; i < npixels; i += rc) {
			if (occ < 4) {
				tif->tif_rawcp = op;
				tif->tif_rawcc = tif->tif_rawdatasize - occ;
				if (!TIFFFlushData1(tif))
					return (-1);
				op = tif->tif_rawcp;
				occ = tif->tif_rawdatasize - tif->tif_rawcc;
			}
			mask = 0xff << shft;		/* find next run */
			for (beg = i; beg < npixels; beg += rc) {
				b = tp[beg] & mask;
				rc = 1;
				while (rc < 127+2 && beg+rc < npixels &&
						(tp[beg+rc] & mask) == b)
					rc++;
				if (rc >= MINRUN)
					break;		/* long enough */
			}
			if (beg-i > 1 && beg-i < MINRUN) {
				b = tp[i] & mask;	/* check short run */
				j = i+1;
				while ((tp[j++] & mask) == b)
					if (j == beg) {
						*op++ = (tidataval_t)(128-2+j-i);
						*op++ = (tidataval_t)(b >> shft);
						occ -= 2;
						i = beg;
						break;
					}
			}
			while (i < beg) {		/* write out non-run */
				if ((j = beg-i) > 127) j = 127;
				if (occ < j+3) {
					tif->tif_rawcp = op;
					tif->tif_rawcc = tif->tif_rawdatasize - occ;
					if (!TIFFFlushData1(tif))
						return (-1);
					op = tif->tif_rawcp;
					occ = tif->tif_rawdatasize - tif->tif_rawcc;
				}
				*op++ = j; occ--;
				while (j--) {
					*op++ = (tidataval_t)(tp[i++] >> shft & 0xff);
					occ--;
				}
			}
			if (rc >= MINRUN) {		/* write out run */
				*op++ = 128-2+rc;
				*op++ = (tidataval_t)(tp[beg] >> shft & 0xff);
				occ -= 2;
			} else
				rc = 0;
		}
	tif->tif_rawcp = op;
	tif->tif_rawcc = tif->tif_rawdatasize - occ;

	return (0);
}

/*
 * Encode a strip of pixels.  We break it into rows to
 * avoid encoding runs across row boundaries.
 */
static int
LogLuvEncodeStrip(TIFF* tif, tidata_t bp, tsize_t cc, tsample_t s)
{
	tsize_t rowlen = TIFFScanlineSize(tif);

	assert(cc%rowlen == 0);
	while (cc && (*tif->tif_encoderow)(tif, bp, rowlen, s) == 0)
		bp += rowlen, cc -= rowlen;
	return (cc == 0);
}

/*
 * Encode a tile of pixels.  We break it into rows to
 * avoid encoding runs across row boundaries.
 */
static int
LogLuvEncodeTile(TIFF* tif, tidata_t bp, tsize_t cc, tsample_t s)
{
	tsize_t rowlen = TIFFTileRowSize(tif);

	assert(cc%rowlen == 0);
	while (cc && (*tif->tif_encoderow)(tif, bp, rowlen, s) == 0)
		bp += rowlen, cc -= rowlen;
	return (cc == 0);
}

/*
 * Encode/Decode functions for converting to and from user formats.
 */

#include "uvcode.h"

#ifndef UVSCALE
#define U_NEU		0.210526316
#define V_NEU		0.473684211
#define UVSCALE		410.
#endif

#ifndef	M_LN2
#define M_LN2		0.69314718055994530942
#endif
#ifndef M_PI
#define M_PI		3.14159265358979323846
#endif
#define log2(x)		((1./M_LN2)*log(x))
#define exp2(x)		exp(M_LN2*(x))

#define itrunc(x,m)	((m)==SGILOGENCODE_NODITHER ? \
				(int)(x) : \
				(int)((x) + rand()*(1./RAND_MAX) - .5))

#if !LOGLUV_PUBLIC
static
#endif
double
LogL16toY(int p16)		/* compute luminance from 16-bit LogL */
{
	int	Le = p16 & 0x7fff;
	double	Y;

	if (!Le)
		return (0.);
	Y = exp(M_LN2/256.*(Le+.5) - M_LN2*64.);
	return (!(p16 & 0x8000) ? Y : -Y);
}

#if !LOGLUV_PUBLIC
static
#endif
int
LogL16fromY(double Y, int em)	/* get 16-bit LogL from Y */
{
	if (Y >= 1.8371976e19)
		return (0x7fff);
	if (Y <= -1.8371976e19)
		return (0xffff);
	if (Y > 5.4136769e-20)
		return itrunc(256.*(log2(Y) + 64.), em);
	if (Y < -5.4136769e-20)
		return (~0x7fff | itrunc(256.*(log2(-Y) + 64.), em));
	return (0);
}

static void
L16toY(LogLuvState* sp, tidata_t op, int n)
{
	int16* l16 = (int16*) sp->tbuf;
	float* yp = (float*) op;

	while (n-- > 0)
		*yp++ = (float)LogL16toY(*l16++);
}

static void
L16toGry(LogLuvState* sp, tidata_t op, int n)
{
	int16* l16 = (int16*) sp->tbuf;
	uint8* gp = (uint8*) op;

	while (n-- > 0) {
		double Y = LogL16toY(*l16++);
		*gp++ = (Y <= 0.) ? 0 : (Y >= 1.) ? 255 : (int)(256.*sqrt(Y));
	}
}

static void
L16fromY(LogLuvState* sp, tidata_t op, int n)
{
	int16* l16 = (int16*) sp->tbuf;
	float* yp = (float*) op;

	while (n-- > 0)
		*l16++ = LogL16fromY(*yp++, sp->encode_meth);
}

#if !LOGLUV_PUBLIC
static
#endif
void
XYZtoRGB24(float xyz[3], uint8 rgb[3])
{
	double	r, g, b;
					/* assume CCIR-709 primaries */
	r =  2.690*xyz[0] + -1.276*xyz[1] + -0.414*xyz[2];
	g = -1.022*xyz[0] +  1.978*xyz[1] +  0.044*xyz[2];
	b =  0.061*xyz[0] + -0.224*xyz[1] +  1.163*xyz[2];
					/* assume 2.0 gamma for speed */
	/* could use integer sqrt approx., but this is probably faster */
	rgb[0] = (r <= 0.) ? 0 : (r >= 1.) ? 255 : (int)(256.*sqrt(r));
	rgb[1] = (g <= 0.) ? 0 : (g >= 1.) ? 255 : (int)(256.*sqrt(g));
	rgb[2] = (b <= 0.) ? 0 : (b >= 1.) ? 255 : (int)(256.*sqrt(b));
}

#if !LOGLUV_PUBLIC
static
#endif
double
LogL10toY(int p10)		/* compute luminance from 10-bit LogL */
{
	if (p10 == 0)
		return (0.);
	return (exp(M_LN2/64.*(p10+.5) - M_LN2*12.));
}

#if !LOGLUV_PUBLIC
static
#endif
int
LogL10fromY(double Y, int em)	/* get 10-bit LogL from Y */
{
	if (Y >= 15.742)
		return (0x3ff);
	else if (Y <= .00024283)
		return (0);
	else
		return itrunc(64.*(log2(Y) + 12.), em);
}

#define NANGLES		100
#define uv2ang(u, v)	( (NANGLES*.499999999/M_PI) \
				* atan2((v)-V_NEU,(u)-U_NEU) + .5*NANGLES )

static int
oog_encode(double u, double v)		/* encode out-of-gamut chroma */
{
	static int	oog_table[NANGLES];
	static int	initialized = 0;
	register int	i;
	
	if (!initialized) {		/* set up perimeter table */
		double	eps[NANGLES], ua, va, ang, epsa;
		int	ui, vi, ustep;
		for (i = NANGLES; i--; )
			eps[i] = 2.;
		for (vi = UV_NVS; vi--; ) {
			va = UV_VSTART + (vi+.5)*UV_SQSIZ;
			ustep = uv_row[vi].nus-1;
			if (vi == UV_NVS-1 || vi == 0 || ustep <= 0)
				ustep = 1;
			for (ui = uv_row[vi].nus-1; ui >= 0; ui -= ustep) {
				ua = uv_row[vi].ustart + (ui+.5)*UV_SQSIZ;
				ang = uv2ang(ua, va);
                                i = (int) ang;
				epsa = fabs(ang - (i+.5));
				if (epsa < eps[i]) {
					oog_table[i] = uv_row[vi].ncum + ui;
					eps[i] = epsa;
				}
			}
		}
		for (i = NANGLES; i--; )	/* fill any holes */
			if (eps[i] > 1.5) {
				int	i1, i2;
				for (i1 = 1; i1 < NANGLES/2; i1++)
					if (eps[(i+i1)%NANGLES] < 1.5)
						break;
				for (i2 = 1; i2 < NANGLES/2; i2++)
					if (eps[(i+NANGLES-i2)%NANGLES] < 1.5)
						break;
				if (i1 < i2)
					oog_table[i] =
						oog_table[(i+i1)%NANGLES];
				else
					oog_table[i] =
						oog_table[(i+NANGLES-i2)%NANGLES];
			}
		initialized = 1;
	}
	i = (int) uv2ang(u, v);		/* look up hue angle */
	return (oog_table[i]);
}

#undef uv2ang
#undef NANGLES

#if !LOGLUV_PUBLIC
static
#endif
int
uv_encode(double u, double v, int em)	/* encode (u',v') coordinates */
{
	register int	vi, ui;

	if (v < UV_VSTART)
		return oog_encode(u, v);
	vi = itrunc((v - UV_VSTART)*(1./UV_SQSIZ), em);
	if (vi >= UV_NVS)
		return oog_encode(u, v);
	if (u < uv_row[vi].ustart)
		return oog_encode(u, v);
	ui = itrunc((u - uv_row[vi].ustart)*(1./UV_SQSIZ), em);
	if (ui >= uv_row[vi].nus)
		return oog_encode(u, v);

	return (uv_row[vi].ncum + ui);
}

#if !LOGLUV_PUBLIC
static
#endif
int
uv_decode(double *up, double *vp, int c)	/* decode (u',v') index */
{
	int	upper, lower;
	register int	ui, vi;

	if (c < 0 || c >= UV_NDIVS)
		return (-1);
	lower = 0;				/* binary search */
	upper = UV_NVS;
	while (upper - lower > 1) {
		vi = (lower + upper) >> 1;
		ui = c - uv_row[vi].ncum;
		if (ui > 0)
			lower = vi;
		else if (ui < 0)
			upper = vi;
		else {
			lower = vi;
			break;
		}
	}
	vi = lower;
	ui = c - uv_row[vi].ncum;
	*up = uv_row[vi].ustart + (ui+.5)*UV_SQSIZ;
	*vp = UV_VSTART + (vi+.5)*UV_SQSIZ;
	return (0);
}

#if !LOGLUV_PUBLIC
static
#endif
void
LogLuv24toXYZ(uint32 p, float XYZ[3])
{
	int	Ce;
	double	L, u, v, s, x, y;
					/* decode luminance */
	L = LogL10toY(p>>14 & 0x3ff);
	if (L <= 0.) {
		XYZ[0] = XYZ[1] = XYZ[2] = 0.;
		return;
	}
					/* decode color */
	Ce = p & 0x3fff;
	if (uv_decode(&u, &v, Ce) < 0) {
		u = U_NEU; v = V_NEU;
	}
	s = 1./(6.*u - 16.*v + 12.);
	x = 9.*u * s;
	y = 4.*v * s;
					/* convert to XYZ */
	XYZ[0] = (float)(x/y * L);
	XYZ[1] = (float)L;
	XYZ[2] = (float)((1.-x-y)/y * L);
}

#if !LOGLUV_PUBLIC
static
#endif
uint32
LogLuv24fromXYZ(float XYZ[3], int em)
{
	int	Le, Ce;
	double	u, v, s;
					/* encode luminance */
	Le = LogL10fromY(XYZ[1], em);
					/* encode color */
	s = XYZ[0] + 15.*XYZ[1] + 3.*XYZ[2];
	if (!Le || s <= 0.) {
		u = U_NEU;
		v = V_NEU;
	} else {
		u = 4.*XYZ[0] / s;
		v = 9.*XYZ[1] / s;
	}
	Ce = uv_encode(u, v, em);
	if (Ce < 0)			/* never happens */
		Ce = uv_encode(U_NEU, V_NEU, SGILOGENCODE_NODITHER);
					/* combine encodings */
	return (Le << 14 | Ce);
}

static void
Luv24toXYZ(LogLuvState* sp, tidata_t op, int n)
{
	uint32* luv = (uint32*) sp->tbuf;
	float* xyz = (float*) op;

	while (n-- > 0) {
		LogLuv24toXYZ(*luv, xyz);
		xyz += 3;
		luv++;
	}
}

static void
Luv24toLuv48(LogLuvState* sp, tidata_t op, int n)
{
	uint32* luv = (uint32*) sp->tbuf;
	int16* luv3 = (int16*) op;

	while (n-- > 0) {
		double u, v;

		*luv3++ = (int16)((*luv >> 12 & 0xffd) + 13314);
		if (uv_decode(&u, &v, *luv&0x3fff) < 0) {
			u = U_NEU;
			v = V_NEU;
		}
		*luv3++ = (int16)(u * (1L<<15));
		*luv3++ = (int16)(v * (1L<<15));
		luv++;
	}
}

static void
Luv24toRGB(LogLuvState* sp, tidata_t op, int n)
{
	uint32* luv = (uint32*) sp->tbuf;
	uint8* rgb = (uint8*) op;

	while (n-- > 0) {
		float xyz[3];

		LogLuv24toXYZ(*luv++, xyz);
		XYZtoRGB24(xyz, rgb);
		rgb += 3;
	}
}

static void
Luv24fromXYZ(LogLuvState* sp, tidata_t op, int n)
{
	uint32* luv = (uint32*) sp->tbuf;
	float* xyz = (float*) op;

	while (n-- > 0) {
		*luv++ = LogLuv24fromXYZ(xyz, sp->encode_meth);
		xyz += 3;
	}
}

static void
Luv24fromLuv48(LogLuvState* sp, tidata_t op, int n)
{
	uint32* luv = (uint32*) sp->tbuf;
	int16* luv3 = (int16*) op;

	while (n-- > 0) {
		int Le, Ce;

		if (luv3[0] <= 0)
			Le = 0;
		else if (luv3[0] >= (1<<12)+3314)
			Le = (1<<10) - 1;
		else if (sp->encode_meth == SGILOGENCODE_NODITHER)
			Le = (luv3[0]-3314) >> 2;
		else
			Le = itrunc(.25*(luv3[0]-3314.), sp->encode_meth);

		Ce = uv_encode((luv[1]+.5)/(1<<15), (luv[2]+.5)/(1<<15),
					sp->encode_meth);
		if (Ce < 0)	/* never happens */
			Ce = uv_encode(U_NEU, V_NEU, SGILOGENCODE_NODITHER);
		*luv++ = (uint32)Le << 14 | Ce;
		luv3 += 3;
	}
}

#if !LOGLUV_PUBLIC
static
#endif
void
LogLuv32toXYZ(uint32 p, float XYZ[3])
{
	double	L, u, v, s, x, y;
					/* decode luminance */
	L = LogL16toY((int)p >> 16);
	if (L <= 0.) {
		XYZ[0] = XYZ[1] = XYZ[2] = 0.;
		return;
	}
					/* decode color */
	u = 1./UVSCALE * ((p>>8 & 0xff) + .5);
	v = 1./UVSCALE * ((p & 0xff) + .5);
	s = 1./(6.*u - 16.*v + 12.);
	x = 9.*u * s;
	y = 4.*v * s;
					/* convert to XYZ */
	XYZ[0] = (float)(x/y * L);
	XYZ[1] = (float)L;
	XYZ[2] = (float)((1.-x-y)/y * L);
}

#if !LOGLUV_PUBLIC
static
#endif
uint32
LogLuv32fromXYZ(float XYZ[3], int em)
{
	unsigned int	Le, ue, ve;
	double	u, v, s;
					/* encode luminance */
	Le = (unsigned int)LogL16fromY(XYZ[1], em);
					/* encode color */
	s = XYZ[0] + 15.*XYZ[1] + 3.*XYZ[2];
	if (!Le || s <= 0.) {
		u = U_NEU;
		v = V_NEU;
	} else {
		u = 4.*XYZ[0] / s;
		v = 9.*XYZ[1] / s;
	}
	if (u <= 0.) ue = 0;
	else ue = itrunc(UVSCALE*u, em);
	if (ue > 255) ue = 255;
	if (v <= 0.) ve = 0;
	else ve = itrunc(UVSCALE*v, em);
	if (ve > 255) ve = 255;
					/* combine encodings */
	return (Le << 16 | ue << 8 | ve);
}