tif_fax3.c

一个国人自己实现图像库的程序（有参考价值）

		 * be initialized to be ``white'' (done elsewhere).
		 */
		esp->refline = (u_char*) _TIFFmalloc(rowbytes);
		if (esp->refline == NULL) {
			TIFFError("Fax3SetupState",
			    "%s: No space for Group 3/4 reference line",
			    tif->tif_name);
			return (0);
		}
	} else					/* 1d encoding */
		EncoderState(tif)->refline = NULL;
	return (1);
}

/*
 * CCITT Group 3 FAX Encoding.
 */

#define	Fax3FlushBits(tif, sp) {				\
	if ((tif)->tif_rawcc >= (tif)->tif_rawdatasize)		\
		(void) TIFFFlushData1(tif);			\
	*(tif)->tif_rawcp++ = (sp)->data;			\
	(tif)->tif_rawcc++;					\
	(sp)->data = 0, (sp)->bit = 8;				\
}
#define	_FlushBits(tif) {					\
	if ((tif)->tif_rawcc >= (tif)->tif_rawdatasize)		\
		(void) TIFFFlushData1(tif);			\
	*(tif)->tif_rawcp++ = data;				\
	(tif)->tif_rawcc++;					\
	data = 0, bit = 8;					\
}
static const int _msbmask[9] =
    { 0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff };
#define	_PutBits(tif, bits, length) {				\
	while (length > bit) {					\
		data |= bits >> (length - bit);			\
		length -= bit;					\
		_FlushBits(tif);				\
	}							\
	data |= (bits & _msbmask[length]) << (bit - length);	\
	bit -= length;						\
	if (bit == 0)						\
		_FlushBits(tif);				\
}
	
/*
 * Write a variable-length bit-value to
 * the output stream.  Values are
 * assumed to be at most 16 bits.
 */
static void
Fax3PutBits(TIFF* tif, u_int bits, u_int length)
{
	Fax3EncodeState* sp = EncoderState(tif);
	u_int bit = sp->bit;
	int data = sp->data;

	_PutBits(tif, bits, length);

	sp->data = data;
	sp->bit = bit;
}

/*
 * Write a code to the output stream.
 */
#define putcode(tif, te)	Fax3PutBits(tif, (te)->code, (te)->length)

#ifdef FAX3_DEBUG
#define	DEBUG_COLOR(w) (tab == TIFFFaxWhiteCodes ? w "W" : w "B")
#define	DEBUG_PRINT(what,len) {						\
    int t;								\
    printf("%08X/%-2d: %s%5d\t", data, bit, DEBUG_COLOR(what), len);	\
    for (t = length-1; t >= 0; t--)					\
	putchar(code & (1<<t) ? '1' : '0');				\
    putchar('\n');							\
}
#endif

/*
 * Write the sequence of codes that describes
 * the specified span of zero's or one's.  The
 * appropriate table that holds the make-up and
 * terminating codes is supplied.
 */
static void
putspan(TIFF* tif, int32 span, const tableentry* tab)
{
	Fax3EncodeState* sp = EncoderState(tif);
	u_int bit = sp->bit;
	int data = sp->data;
	u_int code, length;

	while (span >= 2624) {
		const tableentry* te = &tab[63 + (2560>>6)];
		code = te->code, length = te->length;
#ifdef FAX3_DEBUG
		DEBUG_PRINT("MakeUp", te->runlen);
#endif
		_PutBits(tif, code, length);
		span -= te->runlen;
	}
	if (span >= 64) {
		const tableentry* te = &tab[63 + (span>>6)];
		assert(te->runlen == 64*(span>>6));
		code = te->code, length = te->length;
#ifdef FAX3_DEBUG
		DEBUG_PRINT("MakeUp", te->runlen);
#endif
		_PutBits(tif, code, length);
		span -= te->runlen;
	}
	code = tab[span].code, length = tab[span].length;
#ifdef FAX3_DEBUG
	DEBUG_PRINT("  Term", tab[span].runlen);
#endif
	_PutBits(tif, code, length);

	sp->data = data;
	sp->bit = bit;
}

/*
 * Write an EOL code to the output stream.  The zero-fill
 * logic for byte-aligning encoded scanlines is handled
 * here.  We also handle writing the tag bit for the next
 * scanline when doing 2d encoding.
 */
static void
Fax3PutEOL(TIFF* tif)
{
	Fax3EncodeState* sp = EncoderState(tif);
	u_int bit = sp->bit;
	int data = sp->data;
	u_int code, length, tparm;

	if (sp->b.groupoptions & GROUP3OPT_FILLBITS) {
		/*
		 * Force bit alignment so EOL will terminate on
		 * a byte boundary.  That is, force the bit alignment
		 * to 16-12 = 4 before putting out the EOL code.
		 */
		int align = 8 - 4;
		if (align != sp->bit) {
			if (align > sp->bit)
				align = sp->bit + (8 - align);
			else
				align = sp->bit - align;
			code = 0;
			tparm=align; 
			_PutBits(tif, 0, tparm);
		}
	}
	code = EOL, length = 12;
	if (is2DEncoding(sp))
		code = (code<<1) | (sp->tag == G3_1D), length++;
	_PutBits(tif, code, length);

	sp->data = data;
	sp->bit = bit;
}

/*
 * Reset encoding state at the start of a strip.
 */
static int
Fax3PreEncode(TIFF* tif, tsample_t s)
{
	Fax3EncodeState* sp = EncoderState(tif);

	(void) s;
	assert(sp != NULL);
	sp->bit = 8;
	sp->data = 0;
	sp->tag = G3_1D;
	/*
	 * This is necessary for Group 4; otherwise it isn't
	 * needed because the first scanline of each strip ends
	 * up being copied into the refline.
	 */
	if (sp->refline)
		_TIFFmemset(sp->refline, 0x00, sp->b.rowbytes);
	if (is2DEncoding(sp)) {
		float res = tif->tif_dir.td_yresolution;
		/*
		 * The CCITT spec says that when doing 2d encoding, you
		 * should only do it on K consecutive scanlines, where K
		 * depends on the resolution of the image being encoded
		 * (2 for <= 200 lpi, 4 for > 200 lpi).  Since the directory
		 * code initializes td_yresolution to 0, this code will
		 * select a K of 2 unless the YResolution tag is set
		 * appropriately.  (Note also that we fudge a little here
		 * and use 150 lpi to avoid problems with units conversion.)
		 */
		if (tif->tif_dir.td_resolutionunit == RESUNIT_CENTIMETER)
			res *= 2.54f;		/* convert to inches */
		sp->maxk = (res > 150 ? 4 : 2);
		sp->k = sp->maxk-1;
	} else
		sp->k = sp->maxk = 0;
	return (1);
}

static const u_char zeroruns[256] = {
    8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4,	/* 0x00 - 0x0f */
    3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,	/* 0x10 - 0x1f */
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,	/* 0x20 - 0x2f */
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,	/* 0x30 - 0x3f */
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,	/* 0x40 - 0x4f */
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,	/* 0x50 - 0x5f */
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,	/* 0x60 - 0x6f */
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,	/* 0x70 - 0x7f */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0x80 - 0x8f */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0x90 - 0x9f */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0xa0 - 0xaf */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0xb0 - 0xbf */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0xc0 - 0xcf */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0xd0 - 0xdf */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0xe0 - 0xef */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0xf0 - 0xff */
};
static const u_char oneruns[256] = {
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0x00 - 0x0f */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0x10 - 0x1f */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0x20 - 0x2f */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0x30 - 0x3f */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0x40 - 0x4f */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0x50 - 0x5f */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0x60 - 0x6f */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,	/* 0x70 - 0x7f */
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,	/* 0x80 - 0x8f */
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,	/* 0x90 - 0x9f */
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,	/* 0xa0 - 0xaf */
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,	/* 0xb0 - 0xbf */
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,	/* 0xc0 - 0xcf */
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,	/* 0xd0 - 0xdf */
    3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,	/* 0xe0 - 0xef */
    4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 7, 8,	/* 0xf0 - 0xff */
};

/*
 * On certain systems it pays to inline
 * the routines that find pixel spans.
 */
#ifdef VAXC
static	int32 find0span(u_char*, int32, int32);
static	int32 find1span(u_char*, int32, int32);
#pragma inline(find0span,find1span)
#endif

/*
 * Find a span of ones or zeros using the supplied
 * table.  The ``base'' of the bit string is supplied
 * along with the start+end bit indices.
 */
INLINE static int32
find0span(u_char* bp, int32 bs, int32 be)
{
	int32 bits = be - bs;
	int32 n, span;

	bp += bs>>3;
	/*
	 * Check partial byte on lhs.
	 */
	if (bits > 0 && (n = (bs & 7))) {
		span = zeroruns[(*bp << n) & 0xff];
		if (span > 8-n)		/* table value too generous */
			span = 8-n;
		if (span > bits)	/* constrain span to bit range */
			span = bits;
		if (n+span < 8)		/* doesn't extend to edge of byte */
			return (span);
		bits -= span;
		bp++;
	} else
		span = 0;
	if (bits >= 2*8*sizeof (long)) {
		long* lp;
		/*
		 * Align to longword boundary and check longwords.
		 */
		while (!isAligned(bp, long)) {
			if (*bp != 0x00)
				return (span + zeroruns[*bp]);
			span += 8, bits -= 8;
			bp++;
		}
		lp = (long*) bp;
		while (bits >= 8*sizeof (long) && *lp == 0) {
			span += 8*sizeof (long), bits -= 8*sizeof (long);
			lp++;
		}
		bp = (u_char*) lp;
	}
	/*
	 * Scan full bytes for all 0's.
	 */
	while (bits >= 8) {
		if (*bp != 0x00)	/* end of run */
			return (span + zeroruns[*bp]);
		span += 8, bits -= 8;
		bp++;
	}
	/*
	 * Check partial byte on rhs.
	 */
	if (bits > 0) {
		n = zeroruns[*bp];
		span += (n > bits ? bits : n);
	}
	return (span);
}

INLINE static int32
find1span(u_char* bp, int32 bs, int32 be)
{
	int32 bits = be - bs;
	int32 n, span;

	bp += bs>>3;
	/*
	 * Check partial byte on lhs.
	 */
	if (bits > 0 && (n = (bs & 7))) {
		span = oneruns[(*bp << n) & 0xff];
		if (span > 8-n)		/* table value too generous */
			span = 8-n;
		if (span > bits)	/* constrain span to bit range */
			span = bits;
		if (n+span < 8)		/* doesn't extend to edge of byte */
			return (span);
		bits -= span;
		bp++;
	} else
		span = 0;
	if (bits >= 2*8*sizeof (long)) {
		long* lp;
		/*
		 * Align to longword boundary and check longwords.
		 */
		while (!isAligned(bp, long)) {
			if (*bp != 0xff)
				return (span + oneruns[*bp]);
			span += 8, bits -= 8;
			bp++;
		}
		lp = (long*) bp;
		while (bits >= 8*sizeof (long) && *lp == ~0) {
			span += 8*sizeof (long), bits -= 8*sizeof (long);
			lp++;
		}
		bp = (u_char*) lp;
	}
	/*
	 * Scan full bytes for all 1's.
	 */
	while (bits >= 8) {
		if (*bp != 0xff)	/* end of run */
			return (span + oneruns[*bp]);
		span += 8, bits -= 8;
		bp++;
	}
	/*
	 * Check partial byte on rhs.
	 */
	if (bits > 0) {
		n = oneruns[*bp];
		span += (n > bits ? bits : n);
	}
	return (span);
}

/*
 * Return the offset of the next bit in the range
 * [bs..be] that is different from the specified
 * color.  The end, be, is returned if no such bit
 * exists.
 */
#define	finddiff(_cp, _bs, _be, _color)	\
	(_bs + (_color ? find1span(_cp,_bs,_be) : find0span(_cp,_bs,_be)))
/*
 * Like finddiff, but also check the starting bit
 * against the end in case start > end.
 */
#define	finddiff2(_cp, _bs, _be, _color) \
	(_bs < _be ? finddiff(_cp,_bs,_be,_color) : _be)

/*
 * 1d-encode a row of pixels.  The encoding is
 * a sequence of all-white or all-black spans
 * of pixels encoded with Huffman codes.
 */
static int
Fax3Encode1DRow(TIFF* tif, u_char* bp, uint32 bits)
{
	Fax3EncodeState* sp = EncoderState(tif);
	int32 span;
        uint32 bs = 0;

	for (;;) {
		span = find0span(bp, bs, bits);		/* white span */
		putspan(tif, span, TIFFFaxWhiteCodes);
		bs += span;
		if (bs >= bits)
			break;
		span = find1span(bp, bs, bits);		/* black span */
		putspan(tif, span, TIFFFaxBlackCodes);
		bs += span;
		if (bs >= bits)
			break;
	}
	if (sp->b.mode & (FAXMODE_BYTEALIGN|FAXMODE_WORDALIGN)) {
		if (sp->bit != 8)			/* byte-align */
			Fax3FlushBits(tif, sp);
		if ((sp->b.mode&FAXMODE_WORDALIGN) &&
		    !isAligned(tif->tif_rawcp, uint16))
			Fax3FlushBits(tif, sp);
	}
	return (1);
}

static const tableentry horizcode =
    { 3, 0x1 };		/* 001 */
static const tableentry passcode =
    { 4, 0x1 };		/* 0001 */
static const tableentry vcodes[7] = {
    { 7, 0x03 },	/* 0000 011 */
    { 6, 0x03 },	/* 0000 11 */
    { 3, 0x03 },	/* 011 */
    { 1, 0x1 },		/* 1 */
    { 3, 0x2 },		/* 010 */
    { 6, 0x02 },	/* 0000 10 */
    { 7, 0x02 }		/* 0000 010 */
};

/*
 * 2d-encode a row of pixels.  Consult the CCITT
 * documentation for the algorithm.
 */
static int
Fax3Encode2DRow(TIFF* tif, u_char* bp, u_char* rp, uint32 bits)
{
#define	PIXEL(buf,ix)	((((buf)[(ix)>>3]) >> (7-((ix)&7))) & 1)
        uint32 a0 = 0;
	uint32 a1 = (PIXEL(bp, 0) != 0 ? 0 : finddiff(bp, 0, bits, 0));
	uint32 b1 = (PIXEL(rp, 0) != 0 ? 0 : finddiff(rp, 0, bits, 0));
	uint32 a2, b2;

	for (;;) {
		b2 = finddiff2(rp, b1, bits, PIXEL(rp,b1));
		if (b2 >= a1) {
			int32 d = b1 - a1;
			if (!(-3 <= d && d <= 3)) {	/* horizontal mode */
				a2 = finddiff2(bp, a1, bits, PIXEL(bp,a1));
				putcode(tif, &horizcode);
				if (a0+a1 == 0 || PIXEL(bp, a0) == 0) {
					putspan(tif, a1-a0, TIFFFaxWhiteCodes);
					putspan(tif, a2-a1, TIFFFaxBlackCodes);
				} else {
					putspan(tif, a1-a0, TIFFFaxBlackCodes);
					putspan(tif, a2-a1, TIFFFaxWhiteCodes);
				}
				a0 = a2;
			} else {			/* vertical mode */
				putcode(tif, &vcodes[d+3]);
				a0 = a1;
			}
		} else {				/* pass mode */
			putcode(tif, &passcode);
			a0 = b2;
		}
		if (a0 >= bits)
			break;
		a1 = finddiff(bp, a0, bits, PIXEL(bp,a0));
		b1 = finddiff(rp, a0, bits, !PIXEL(bp,a0));
		b1 = finddiff(rp, b1, bits, PIXEL(bp,a0));
	}
	return (1);
#undef PIXEL
}

/*
 * Encode a buffer of pixels.
 */
static int
Fax3Encode(TIFF* tif, tidata_t bp, tsize_t cc, tsample_t s)
{
	Fax3EncodeState* sp = EncoderState(tif);

	(void) s;
	while ((long)cc > 0) {
		if ((sp->b.mode & FAXMODE_NOEOL) == 0)
			Fax3PutEOL(tif);
		if (is2DEncoding(sp)) {
			if (sp->tag == G3_1D) {
				if (!Fax3Encode1DRow(tif, bp, sp->b.rowpixels))
					return (0);
				sp->tag = G3_2D;
			} else {
				if (!Fax3Encode2DRow(tif, bp, sp->refline, sp->b.rowpixels))
					return (0);
				sp->k--;
			}
			if (sp->k == 0) {
				sp->tag = G3_1D;
				sp->k = sp->maxk-1;
			} else
				_TIFFmemcpy(sp->refline, bp, sp->b.rowbytes);
		} else {
			if (!Fax3Encode1DRow(tif, bp, sp->b.rowpixels))
				return (0);