tif_fax3.h

一个国人自己实现图像库的程序（有参考价值）

/* $Id: tif_fax3.h,v 1.4 2000/12/01 15:46:46 warmerda Exp $ */

/*
 * Copyright (c) 1990-1997 Sam Leffler
 * Copyright (c) 1991-1997 Silicon Graphics, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software and 
 * its documentation for any purpose is hereby granted without fee, provided
 * that (i) the above copyright notices and this permission notice appear in
 * all copies of the software and related documentation, and (ii) the names of
 * Sam Leffler and Silicon Graphics may not be used in any advertising or
 * publicity relating to the software without the specific, prior written
 * permission of Sam Leffler and Silicon Graphics.
 * 
 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY 
 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  
 * 
 * IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
 * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
 * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF 
 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 
 * OF THIS SOFTWARE.
 */

#ifndef _FAX3_
#define	_FAX3_
/*
 * TIFF Library.
 *
 * CCITT Group 3 (T.4) and Group 4 (T.6) Decompression Support.
 *
 * Decoder support is derived, with permission, from the code
 * in Frank Cringle's viewfax program;
 *      Copyright (C) 1990, 1995  Frank D. Cringle.
 */
#include "tiff.h"

/*
 * To override the default routine used to image decoded
 * spans one can use the pseduo tag TIFFTAG_FAXFILLFUNC.
 * The routine must have the type signature given below;
 * for example:
 *
 * fillruns(unsigned char* buf, uint32* runs, uint32* erun, uint32 lastx)
 *
 * where buf is place to set the bits, runs is the array of b&w run
 * lengths (white then black), erun is the last run in the array, and
 * lastx is the width of the row in pixels.  Fill routines can assume
 * the run array has room for at least lastx runs and can overwrite
 * data in the run array as needed (e.g. to append zero runs to bring
 * the count up to a nice multiple).
 */
typedef	void (*TIFFFaxFillFunc)(unsigned char*, uint32*, uint32*, uint32);

/*
 * The default run filler; made external for other decoders.
 */
#if defined(__cplusplus)
extern "C" {
#endif
extern	void _TIFFFax3fillruns(unsigned char*, uint32*, uint32*, uint32);
#if defined(__cplusplus)
}
#endif


/* finite state machine codes */
#define S_Null		0
#define S_Pass		1
#define S_Horiz		2
#define S_V0		3
#define S_VR		4
#define S_VL		5
#define S_Ext		6
#define S_TermW		7
#define S_TermB		8
#define S_MakeUpW	9
#define S_MakeUpB	10
#define S_MakeUp	11
#define S_EOL		12

typedef struct {		/* state table entry */
	unsigned char State;	/* see above */
	unsigned char Width;	/* width of code in bits */
	uint32	Param;		/* unsigned 32-bit run length in bits */
} TIFFFaxTabEnt;

extern	const TIFFFaxTabEnt TIFFFaxMainTable[];
extern	const TIFFFaxTabEnt TIFFFaxWhiteTable[];
extern	const TIFFFaxTabEnt TIFFFaxBlackTable[];

/*
 * The following macros define the majority of the G3/G4 decoder
 * algorithm using the state tables defined elsewhere.  To build
 * a decoder you need some setup code and some glue code. Note
 * that you may also need/want to change the way the NeedBits*
 * macros get input data if, for example, you know the data to be
 * decoded is properly aligned and oriented (doing so before running
 * the decoder can be a big performance win).
 *
 * Consult the decoder in the TIFF library for an idea of what you
 * need to define and setup to make use of these definitions.
 *
 * NB: to enable a debugging version of these macros define FAX3_DEBUG
 *     before including this file.  Trace output goes to stdout.
 */

#ifndef EndOfData
#define EndOfData()	(cp >= ep)
#endif
/*
 * Need <=8 or <=16 bits of input data.  Unlike viewfax we
 * cannot use/assume a word-aligned, properly bit swizzled
 * input data set because data may come from an arbitrarily
 * aligned, read-only source such as a memory-mapped file.
 * Note also that the viewfax decoder does not check for
 * running off the end of the input data buffer.  This is
 * possible for G3-encoded data because it prescans the input
 * data to count EOL markers, but can cause problems for G4
 * data.  In any event, we don't prescan and must watch for
 * running out of data since we can't permit the library to
 * scan past the end of the input data buffer.
 *
 * Finally, note that we must handle remaindered data at the end
 * of a strip specially.  The coder asks for a fixed number of
 * bits when scanning for the next code.  This may be more bits
 * than are actually present in the data stream.  If we appear
 * to run out of data but still have some number of valid bits
 * remaining then we makeup the requested amount with zeros and
 * return successfully.  If the returned data is incorrect then
 * we should be called again and get a premature EOF error;
 * otherwise we should get the right answer.
 */
#ifndef NeedBits8
#define NeedBits8(n,eoflab) do {					\
    if (BitsAvail < (n)) {						\
	if (EndOfData()) {						\
	    if (BitsAvail == 0)			/* no valid bits */	\
		goto eoflab;						\
	    BitsAvail = (n);			/* pad with zeros */	\
	} else {							\
	    BitAcc |= ((uint32) bitmap[*cp++])<<BitsAvail;		\
	    BitsAvail += 8;						\
	}								\
    }									\
} while (0)
#endif
#ifndef NeedBits16
#define NeedBits16(n,eoflab) do {					\
    if (BitsAvail < (n)) {						\
	if (EndOfData()) {						\
	    if (BitsAvail == 0)			/* no valid bits */	\
		goto eoflab;						\
	    BitsAvail = (n);			/* pad with zeros */	\
	} else {							\
	    BitAcc |= ((uint32) bitmap[*cp++])<<BitsAvail;		\
	    if ((BitsAvail += 8) < (n)) {				\
		if (EndOfData()) {					\
		    /* NB: we know BitsAvail is non-zero here */	\
		    BitsAvail = (n);		/* pad with zeros */	\
		} else {						\
		    BitAcc |= ((uint32) bitmap[*cp++])<<BitsAvail;	\
		    BitsAvail += 8;					\
		}							\
	    }								\
	}								\
    }									\
} while (0)
#endif
#define GetBits(n)	(BitAcc & ((1<<(n))-1))
#define ClrBits(n) do {							\
    BitsAvail -= (n);							\
    BitAcc >>= (n);							\
} while (0)

#ifdef FAX3_DEBUG
static const char* StateNames[] = {
    "Null   ",
    "Pass   ",
    "Horiz  ",
    "V0     ",
    "VR     ",
    "VL     ",
    "Ext    ",
    "TermW  ",
    "TermB  ",
    "MakeUpW",
    "MakeUpB",
    "MakeUp ",
    "EOL    ",
};
#define DEBUG_SHOW putchar(BitAcc & (1 << t) ? '1' : '0')
#define LOOKUP8(wid,tab,eoflab) do {					\
    int t;								\
    NeedBits8(wid,eoflab);						\
    TabEnt = tab + GetBits(wid);					\
    printf("%08lX/%d: %s%5d\t", (long) BitAcc, BitsAvail,		\
	   StateNames[TabEnt->State], TabEnt->Param);			\
    for (t = 0; t < TabEnt->Width; t++)					\
	DEBUG_SHOW;							\
    putchar('\n');							\
    fflush(stdout);							\
    ClrBits(TabEnt->Width);						\
} while (0)
#define LOOKUP16(wid,tab,eoflab) do {					\
    int t;								\
    NeedBits16(wid,eoflab);						\
    TabEnt = tab + GetBits(wid);					\
    printf("%08lX/%d: %s%5d\t", (long) BitAcc, BitsAvail,		\
	   StateNames[TabEnt->State], TabEnt->Param);			\
    for (t = 0; t < TabEnt->Width; t++)					\
	DEBUG_SHOW;							\
    putchar('\n');							\
    fflush(stdout);							\
    ClrBits(TabEnt->Width);						\
} while (0)

#define SETVAL(x) do {							\
    *pa++ = RunLength + (x);						\
    printf("SETVAL: %d\t%d\n", RunLength + (x), a0);			\
    a0 += x;								\
    RunLength = 0;							\
} while (0)
#else
#define LOOKUP8(wid,tab,eoflab) do {					\
    NeedBits8(wid,eoflab);						\
    TabEnt = tab + GetBits(wid);					\
    ClrBits(TabEnt->Width);						\
} while (0)
#define LOOKUP16(wid,tab,eoflab) do {					\
    NeedBits16(wid,eoflab);						\
    TabEnt = tab + GetBits(wid);					\
    ClrBits(TabEnt->Width);						\
} while (0)

/*
 * Append a run to the run length array for the
 * current row and reset decoding state.
 */
#define SETVAL(x) do {							\
    *pa++ = RunLength + (x);						\
    a0 += (x);								\
    RunLength = 0;							\
} while (0)
#endif

/*
 * Synchronize input decoding at the start of each
 * row by scanning for an EOL (if appropriate) and
 * skipping any trash data that might be present
 * after a decoding error.  Note that the decoding
 * done elsewhere that recognizes an EOL only consumes
 * 11 consecutive zero bits.  This means that if EOLcnt
 * is non-zero then we still need to scan for the final flag
 * bit that is part of the EOL code.
 */
#define	SYNC_EOL(eoflab) do {						\
    if (EOLcnt == 0) {							\
	for (;;) {							\
	    NeedBits16(11,eoflab);					\
	    if (GetBits(11) == 0)					\