src/common/tonemap.h

/* Copyright (c) 1998 Silicon Graphics, Inc. */

/* SCCSid "$SunId$ SGI" */

/*
 * Header file for tone mapping functions.
 *
 * Include after "color.h"
 */


/****    Argument Macros    ****/
                                /* Flags of what to do */
#define TM_F_HCONTR     01              /* human contrast sensitivity */
#define TM_F_MESOPIC    02              /* mesopic color sensitivity */
#define TM_F_LINEAR     04              /* linear brightness mapping */
#define TM_F_ACUITY     010             /* acuity adjustment */
#define TM_F_VEIL       020             /* veiling glare */
#define TM_F_CWEIGHT    040             /* center weighting */
#define TM_F_FOVEAL     0100            /* use foveal sample size */
#define TM_F_BW         0200            /* luminance only */
#define TM_F_NOSTDERR   0400            /* don't report errors to stderr */
                                /* combined modes */
#define TM_F_CAMERA     0
#define TM_F_HUMAN      (TM_F_HCONTR|TM_F_MESOPIC|TM_F_VEIL|\
                                TM_F_ACUITY|TM_F_FOVEAL)
#define TM_F_UNIMPL     (TM_F_CWEIGHT|TM_F_VEIL|TM_F_ACUITY|TM_F_FOVEAL)

                                /* special pointer values */
#define TM_XYZPRIM      (RGBPRIMP)NULL  /* indicate XYZ primaries (Note 1) */
#define TM_NOCHROM      (BYTE *)NULL    /* indicate no chrominance */
#define TM_NOCHROMP     (BYTE **)NULL   /* indicate no chrominances */
#define TM_GETFILE      (FILE *)NULL    /* indicate file must be opened */


/****    Error Return Values    ****/

#define TM_E_OK         0               /* normal return status */
#define TM_E_NOMEM      1               /* out of memory */
#define TM_E_ILLEGAL    2               /* illegal argument value */
#define TM_E_TMINVAL    3               /* no valid tone mapping */
#define TM_E_TMFAIL     4               /* cannot compute tone mapping */
#define TM_E_BADFILE    5               /* cannot open or understand file */
#define TM_E_CODERR1    6               /* code consistency error 1 */
#define TM_E_CODERR2    7               /* code consistency error 2 */


/****    Conversion Constants and Table Sizes    ****/

#define TM_BRTSCALE     128             /* brightness scale factor (integer) */

#define TM_MAXPKG       8               /* maximum number of color formats */


/****    Global Data Types and Structures    ****/

#ifndef MEM_PTR
#define MEM_PTR         void *
#endif

extern char     *tmErrorMessage[];      /* error messages */
extern int      tmLastError;            /* last error incurred by library */
extern char     *tmLastFunction;        /* error-generating function name */

typedef short   TMbright;               /* encoded luminance type */

                                /* basic tone mapping data structure */
extern struct tmStruct {
        int             flags;          /* flags of what to do */
        RGBPRIMP        monpri;         /* monitor RGB primaries */
        double          mongam;         /* monitor gamma value (approx.) */
        COLOR           clf;            /* computed luminance coefficients */
        int             cdiv[3];        /* computed color divisors */
        RGBPRIMP        inppri;         /* current input primaries */
        double          inpsf;          /* current input scalefactor */
        COLORMAT        cmat;           /* color conversion matrix */
        TMbright        hbrmin, hbrmax; /* histogram brightness limits */       
        int             *histo;         /* input histogram */
        TMbright        mbrmin, mbrmax; /* mapped brightness limits */
        unsigned short  *lumap;         /* computed luminance map */
        struct tmStruct *tmprev;        /* previous tone mapping */
        MEM_PTR         pd[TM_MAXPKG];  /* pointers to private data */
}       *tmTop;                 /* current tone mapping stack */

                                /* conversion package functions */
#ifdef  NOPROTO
struct tmPackage {
        MEM_PTR         (*Init)();      /* initialize private data */
        void            (*NewSpace)();  /* new input color space (optional) */
        void            (*Free)();      /* free private data */
};
#else
struct tmPackage {
        MEM_PTR         (*Init)(struct tmStruct *tms);
        int             (*NewSpace)(struct tmStruct *tms);
        void            (*Free)(MEM_PTR pp);
};
#endif
                                /* our list of conversion packages */
extern struct tmPackage *tmPkg[TM_MAXPKG];
extern int      tmNumPkgs;      /* number of registered packages */


/****    Useful Macros    ****/

                                /* compute luminance from encoded value */
#define tmLuminance(li) exp((li)/(double)TM_BRTSCALE)

                                /* does tone mapping need color matrix? */
#define tmNeedMatrix(t) ((t)->monpri != (t)->inppri)

                                /* register a conversion package */
#define tmRegPkg(pf)    ( tmNumPkgs >= TM_MAXPKG ? -1 : \
                                (tmPkg[tmNumPkgs] = (pf), tmNumPkgs++) )

                                /* get the specific package's data */
#define tmPkgData(t,i)  ((t)->pd[i]!=NULL ? (t)->pd[i] : (*tmPkg[i]->Init)(t))


/****    Library Function Calls    ****/

#ifdef  NOPROTO

extern struct tmStruct  *tmInit(), *tmPop(), *tmDup();
extern void     tmClearHisto(), tmDone();
extern int      tmSetSpace(), tmCvColors(), tmCvColrs();
extern int      tmAddHisto(), tmComputeMapping(), tmMapPixels();
extern int      tmLoadPicture(), tmMapPicture(), tmPull(), tmPush();

#else

extern struct tmStruct *
tmInit(int flags, RGBPRIMP monpri, double gamval);
/*
        Initialize new tone mapping and push it onto stack.

        flags   -       TM_F_* flags indicating what is to be done.
        monpri  -       display monitor primaries (Note 1).
        gamval  -       display gamma response (can be approximate).

        returns -       new tmTop, or NULL if insufficient memory.
*/

extern int
tmSetSpace(RGBPRIMP pri, double sf);
/*
        Set color primaries and scale factor for incoming scanlines.

        pri     -       RGB color input primaries (Note 1).
        sf      -       scale factor to get to luminance in cd/m^2.

        returns -       0 on success, TM_E_* code on failure.
*/

extern void
tmClearHisto(void);
/*
        Clear histogram for current tone mapping.
*/

extern int
tmCvColors(TMbright *ls, BYTE *cs, COLOR *scan, int len);
/*
        Convert RGB/XYZ float scanline to encoded luminance and chrominance.

        ls      -       returned encoded luminance values.
        cs      -       returned encoded chrominance values (Note 2).
        scan    -       input scanline.
        len     -       scanline length.

        returns -       0 on success, TM_E_* on error.
*/

extern int
tmCvColrs(TMbright *ls, BYTE *cs, COLR *scan, int len);
/*
        Convert RGBE/XYZE scanline to encoded luminance and chrominance.

        ls      -       returned encoded luminance values.
        cs      -       returned encoded chrominance values (Note 2).
        scan    -       input scanline.
        len     -       scanline length.

        returns -       0 on success, TM_E_* on error.
*/

extern int
tmAddHisto(TMbright *ls, int len, int wt);
/*
        Add brightness values to current histogram.

        ls      -       encoded luminance values.
        len     -       number of luminance values.
        wt      -       integer weight to use for each value (usually 1 or -1).

        returns -       0 on success, TM_E_* on error.
*/

extern int
tmComputeMapping(double gamval, double Lddyn, double Ldmax);
/*
        Compute tone mapping function.  This mapping will be used
        in subsequent calls to tmMapPixels() until a new tone mapping
        is computed.  I.e., calls to tmAddHisto() have no immediate effect.

        gamval  -       display gamma response (0. for default).
        Lddyn   -       the display's dynamic range (0. for default).
        Ldmax   -       maximum display luminance in cd/m^2 (0. for default).

        returns -       0 on success, TM_E_* on failure.
*/

extern int
tmMapPixels(BYTE *ps, TMbright *ls, BYTE *cs, int len);
/*
        Apply tone mapping function to pixel values.

        ps      -       returned pixel values (Note 2).
        ls      -       encoded luminance values.
        cs      -       encoded chrominance values (Note 2).
        len     -       number of pixels.

        returns -       0 on success, TM_E_* on failure.
*/

extern int
tmLoadPicture(TMbright **lpp, BYTE **cpp, int *xp, int *yp,
                char *fname, FILE *fp);
/*
        Load Radiance picture and convert to tone mapping representation.
        Memory for the luminance and chroma arrays is allocated using
        malloc(3), and should be freed with free(3) when no longer needed.
        Calls tmSetSpace() to calibrate input color space.

        lpp     -       returned array of encoded luminances, picture ordering.
        cpp     -       returned array of encoded chrominances (Note 2).
        xp, yp  -       returned picture dimensions.
        fname   -       picture file name.
        fp      -       pointer to open file (Note 3).

        returns -       0 on success, TM_E_* on failure.
*/

extern int
tmMapPicture(BYTE **psp, int *xp, int *yp, int flags,
                RGBPRIMP monpri, double gamval, double Lddyn, double Ldmax,
                char *fname, FILE *fp);
/*
        Load and apply tone mapping to Radiance picture.
        Stack is restored to its original state upon return.
        If fp is TM_GETFILE and (flags&TM_F_UNIMPL)!=0, tmMapPicture()
        calls pcond to perform the actual conversion, which takes
        longer but gives access to all the TM_F_* features.
        Memory for the final pixel array is allocated using malloc(3),
        and should be freed with free(3) when it is no longer needed.

        psp     -       returned array of tone mapped pixels, picture ordering.
        xp, yp  -       returned picture dimensions.
        flags   -       TM_F_* flags indicating what is to be done.
        monpri  -       display monitor primaries (Note 1).
        gamval  -       display gamma response.
        Lddyn   -       the display's dynamic range (0. for default).
        Ldmax   -       maximum display luminance in cd/m^2 (0. for default).
        fname   -       picture file name.
        fp      -       pointer to open file (Note 3).

        returns -       0 on success, TM_E_* on failure.
*/

extern struct tmStruct *
tmPop(void);
/*
        Pops current tone mapping from stack.

        returns -       pointer to tone mapping structure, or NULL if none.
*/

extern int
tmPull(struct tmStruct *tms);
/*
        Pull tone mapping from anywhere in stack.

        tms     -       tone mapping structure to find.

        returns -       1 if found in stack, 0 otherwise.
*/

extern int
tmPush(struct tmStruct *tms);
/*
        Make tone mapping active by (pulling it and) pushing it to the top.

        tms     -       initialized tone mapping structure.

        returns -       0 on success, TM_E_* if tms is invalid.
*/

extern struct tmStruct *
tmDup(void);
/*
        Duplicate the current tone mapping into a new structure on the stack.

        returns -       pointer to new top, or NULL on error.
*/

extern void
tmDone(struct tmStruct *tms);
/*
        Free data associated with the given tone mapping structure.
        Calls tmPull() first to remove it from the stack if present.
        The calls tmDone(tmPop()), tmDone(tmTop) and tmDone(NULL)
        all have the same effect, which is to remove and free
        the current tone mapping.

        tms     -       tone mapping structure to free.
*/

#endif


/****    Notes    ****/
/*
        General:

        The usual sequence after calling tmInit() is to convert some
        pixel values to chroma and luminance encodings, which can
        be passed to tmAddHisto() to put into the tone mapping histogram.
        This histogram is then used along with the display parameters
        by tmComputeMapping() to compute the luminance mapping function.
        (Colors are tone-mapped as they are converted if TM_F_MESOPIC
        is set.)  The encoded chroma and luminance values may then be
        passed to tmMapPixels() to apply the computed tone mapping in
        a second pass.

        Especially for RGBE colors in the same color space as the
        target display, the conversion to chroma and luminance values
        is fast enough that it may be recomputed on the second pass
        if memory is at a premium.  (Since the chroma values are only
        used during final mapping, setting the cs parameter to TM_NOCHROM
        on the first pass will save time.)  Another memory saving option
        if third and subsequent passes are not needed is to use the
        same array to store the mapped pixels as used to store
        the encoded chroma values.  This way, only two extra bytes
        for storing encoded luminances are required per pixel.  This
        is the method employed by tmMapPicture(), for example.
*/
/*
        Note 1:

        All RGBPRIMP values should be pointers to static structures.
        I.e., the same pointer should be used for the same primaries,
        and those primaries should not change from one call to the next.
        This is because the routines use the pointer value to identify
        computed conversion matrices, so the matrices do not have to be
        rebuilt each time.  If you are using the standard primaries,
        use the standard primary pointer, stdprims.

        To indicate a set of input primaries are actually CIE XYZ,
        the TM_XYZPRIM macro may be passed.  If the input primaries
        are unknown, it is wisest to pass tmTop->monpri to tmSetSpace().
        By default, the input primaries equal the monitor primaries
        and the scalefactor is set to WHTEFFICACY in tmInit().
*/
/*
        Note 2:

        Chrominance is optional in most of these routines, whether
        TM_F_BW is set or not.  Passing a value of TM_NOCHROM (or
        TM_NOCHROMP for picture reading) indicates that returned
        color values are not desired.
        
        If TM_NOCHROM is passed to a mapping routine expecting chroma
        input, it will do without it and return luminance channel
        rather than RGB pixel values.  Otherwise, the array for
        returned pixel values may be the same array used to pass
        encoded chrominances if no other mappings are desired.
*/
/*
        Note 3:

        Picture files may either be opened by the calling routine or by
        the library function.  If opened by the calling routine, the
        pointer to the stream is passed, which may be a pipe or other
        non-seekable input as it is only read once.  It must be
        positioned at the beginning when the function is called, and it
        will be positioned at the end on return.  It will not be closed.
        If the passed stream pointer is TM_GETFILE, then the library
        function will open the file, read its contents and close it
        before returning, whether or not an error was encountered.
*/
Revision:	3.9
Committed:	Mon Oct 5 16:49:52 1998 UTC (27 years ago) by gwlarson
Content type:	text/plain
Branch:	MAIN
Changes since 3.8:	+2 -2 lines
Log Message:	corrected comment about pixel ordering for tmLoadPicture and tmMapPicture
#	User	Rev	Content
1	gwlarson	3.8	/* Copyright (c) 1998 Silicon Graphics, Inc. */
2	greg	3.1
3	gwlarson	3.8	/* SCCSid "$SunId$ SGI" */
4	greg	3.1
5			/*
6			* Header file for tone mapping functions.
7	gwlarson	3.8	*
8			* Include after "color.h"
9	greg	3.1	*/
10
11	greg	3.4
12	greg	3.1	/** Argument Macros **/
13			/* Flags of what to do */
14			#define TM_F_HCONTR 01 /* human contrast sensitivity */
15			#define TM_F_MESOPIC 02 /* mesopic color sensitivity */
16			#define TM_F_LINEAR 04 /* linear brightness mapping */
17			#define TM_F_ACUITY 010 /* acuity adjustment */
18			#define TM_F_VEIL 020 /* veiling glare */
19			#define TM_F_CWEIGHT 040 /* center weighting */
20			#define TM_F_FOVEAL 0100 /* use foveal sample size */
21			#define TM_F_BW 0200 /* luminance only */
22	greg	3.2	#define TM_F_NOSTDERR 0400 /* don't report errors to stderr */
23	greg	3.1	/* combined modes */
24			#define TM_F_CAMERA 0
25			#define TM_F_HUMAN (TM_F_HCONTR\|TM_F_MESOPIC\|TM_F_VEIL\|\
26			TM_F_ACUITY\|TM_F_FOVEAL)
27			#define TM_F_UNIMPL (TM_F_CWEIGHT\|TM_F_VEIL\|TM_F_ACUITY\|TM_F_FOVEAL)
28
29			/* special pointer values */
30			#define TM_XYZPRIM (RGBPRIMP)NULL /* indicate XYZ primaries (Note 1) */
31			#define TM_NOCHROM (BYTE )NULL / indicate no chrominance */
32			#define TM_NOCHROMP (BYTE *)NULL / indicate no chrominances */
33			#define TM_GETFILE (FILE )NULL / indicate file must be opened */
34	gwlarson	3.8
35	greg	3.1
36			/** Error Return Values **/
37
38			#define TM_E_OK 0 /* normal return status */
39			#define TM_E_NOMEM 1 /* out of memory */
40			#define TM_E_ILLEGAL 2 /* illegal argument value */
41			#define TM_E_TMINVAL 3 /* no valid tone mapping */
42			#define TM_E_TMFAIL 4 /* cannot compute tone mapping */
43			#define TM_E_BADFILE 5 /* cannot open or understand file */
44	greg	3.4	#define TM_E_CODERR1 6 /* code consistency error 1 */
45			#define TM_E_CODERR2 7 /* code consistency error 2 */
46	greg	3.1
47	greg	3.4
48	greg	3.1	/** Conversion Constants and Table Sizes **/
49
50			#define TM_BRTSCALE 128 /* brightness scale factor (integer) */
51
52	greg	3.4	#define TM_MAXPKG 8 /* maximum number of color formats */
53	greg	3.1
54
55	greg	3.4	/** Global Data Types and Structures **/
56
57			#ifndef MEM_PTR
58			#define MEM_PTR void *
59			#endif
60
61	greg	3.1	extern char tmErrorMessage[]; / error messages */
62	gregl	3.6	extern int tmLastError; /* last error incurred by library */
63			extern char tmLastFunction; / error-generating function name */
64	greg	3.1
65			typedef short TMbright; /* encoded luminance type */
66
67			/* basic tone mapping data structure */
68			extern struct tmStruct {
69			int flags; /* flags of what to do */
70			RGBPRIMP monpri; /* monitor RGB primaries */
71			double mongam; /* monitor gamma value (approx.) */
72			COLOR clf; /* computed luminance coefficients */
73	greg	3.4	int cdiv[3]; /* computed color divisors */
74	greg	3.1	RGBPRIMP inppri; /* current input primaries */
75			double inpsf; /* current input scalefactor */
76			COLORMAT cmat; /* color conversion matrix */
77	gregl	3.7	TMbright hbrmin, hbrmax; /* histogram brightness limits */
78	greg	3.1	int histo; / input histogram */
79	gregl	3.7	TMbright mbrmin, mbrmax; /* mapped brightness limits */
80	greg	3.1	unsigned short lumap; / computed luminance map */
81			struct tmStruct tmprev; / previous tone mapping */
82	greg	3.4	MEM_PTR pd[TM_MAXPKG]; /* pointers to private data */
83	greg	3.1	} tmTop; / current tone mapping stack */
84	greg	3.4
85			/* conversion package functions */
86			#ifdef NOPROTO
87			struct tmPackage {
88			MEM_PTR (Init)(); / initialize private data */
89			void (NewSpace)(); / new input color space (optional) */
90			void (Free)(); / free private data */
91			};
92			#else
93			struct tmPackage {
94			MEM_PTR (Init)(struct tmStruct tms);
95			int (NewSpace)(struct tmStruct tms);
96			void (*Free)(MEM_PTR pp);
97			};
98			#endif
99			/* our list of conversion packages */
100			extern struct tmPackage *tmPkg[TM_MAXPKG];
101			extern int tmNumPkgs; /* number of registered packages */
102
103
104	greg	3.1	/** Useful Macros **/
105
106	greg	3.4	/* compute luminance from encoded value */
107	greg	3.1	#define tmLuminance(li) exp((li)/(double)TM_BRTSCALE)
108
109	greg	3.4	/* does tone mapping need color matrix? */
110			#define tmNeedMatrix(t) ((t)->monpri != (t)->inppri)
111
112			/* register a conversion package */
113			#define tmRegPkg(pf) ( tmNumPkgs >= TM_MAXPKG ? -1 : \
114			(tmPkg[tmNumPkgs] = (pf), tmNumPkgs++) )
115
116			/* get the specific package's data */
117			#define tmPkgData(t,i) ((t)->pd[i]!=NULL ? (t)->pd[i] : (*tmPkg[i]->Init)(t))
118
119
120	greg	3.1	/** Library Function Calls **/
121
122	greg	3.4	#ifdef NOPROTO
123	greg	3.1
124	greg	3.3	extern struct tmStruct tmInit(), tmPop(), *tmDup();
125	greg	3.1	extern void tmClearHisto(), tmDone();
126			extern int tmSetSpace(), tmCvColors(), tmCvColrs();
127			extern int tmAddHisto(), tmComputeMapping(), tmMapPixels();
128			extern int tmLoadPicture(), tmMapPicture(), tmPull(), tmPush();
129
130			#else
131
132			extern struct tmStruct *
133			tmInit(int flags, RGBPRIMP monpri, double gamval);
134			/*
135			Initialize new tone mapping and push it onto stack.
136
137			flags - TM_F_* flags indicating what is to be done.
138			monpri - display monitor primaries (Note 1).
139			gamval - display gamma response (can be approximate).
140
141			returns - new tmTop, or NULL if insufficient memory.
142			*/
143
144			extern int
145			tmSetSpace(RGBPRIMP pri, double sf);
146			/*
147			Set color primaries and scale factor for incoming scanlines.
148
149			pri - RGB color input primaries (Note 1).
150			sf - scale factor to get to luminance in cd/m^2.
151
152			returns - 0 on success, TM_E_* code on failure.
153			*/
154
155			extern void
156			tmClearHisto(void);
157			/*
158			Clear histogram for current tone mapping.
159			*/
160
161			extern int
162			tmCvColors(TMbright ls, BYTE cs, COLOR *scan, int len);
163			/*
164			Convert RGB/XYZ float scanline to encoded luminance and chrominance.
165
166			ls - returned encoded luminance values.
167			cs - returned encoded chrominance values (Note 2).
168			scan - input scanline.
169			len - scanline length.
170
171			returns - 0 on success, TM_E_* on error.
172			*/
173
174			extern int
175			tmCvColrs(TMbright ls, BYTE cs, COLR *scan, int len);
176			/*
177			Convert RGBE/XYZE scanline to encoded luminance and chrominance.
178
179			ls - returned encoded luminance values.
180			cs - returned encoded chrominance values (Note 2).
181			scan - input scanline.
182			len - scanline length.
183
184			returns - 0 on success, TM_E_* on error.
185			*/
186
187			extern int
188			tmAddHisto(TMbright *ls, int len, int wt);
189			/*
190			Add brightness values to current histogram.
191
192			ls - encoded luminance values.
193			len - number of luminance values.
194			wt - integer weight to use for each value (usually 1 or -1).
195
196			returns - 0 on success, TM_E_* on error.
197			*/
198
199			extern int
200			tmComputeMapping(double gamval, double Lddyn, double Ldmax);
201			/*
202	gregl	3.7	Compute tone mapping function. This mapping will be used
203			in subsequent calls to tmMapPixels() until a new tone mapping
204			is computed. I.e., calls to tmAddHisto() have no immediate effect.
205	greg	3.1
206			gamval - display gamma response (0. for default).
207			Lddyn - the display's dynamic range (0. for default).
208			Ldmax - maximum display luminance in cd/m^2 (0. for default).
209
210			returns - 0 on success, TM_E_* on failure.
211			*/
212
213			extern int
214			tmMapPixels(BYTE ps, TMbright ls, BYTE *cs, int len);
215			/*
216			Apply tone mapping function to pixel values.
217
218			ps - returned pixel values (Note 2).
219			ls - encoded luminance values.
220			cs - encoded chrominance values (Note 2).
221			len - number of pixels.
222
223			returns - 0 on success, TM_E_* on failure.
224			*/
225
226			extern int
227			tmLoadPicture(TMbright lpp, BYTE cpp, int xp, int yp,
228			char fname, FILE fp);
229			/*
230			Load Radiance picture and convert to tone mapping representation.
231	greg	3.5	Memory for the luminance and chroma arrays is allocated using
232			malloc(3), and should be freed with free(3) when no longer needed.
233	greg	3.3	Calls tmSetSpace() to calibrate input color space.
234	greg	3.1
235	gwlarson	3.9	lpp - returned array of encoded luminances, picture ordering.
236	greg	3.1	cpp - returned array of encoded chrominances (Note 2).
237			xp, yp - returned picture dimensions.
238			fname - picture file name.
239			fp - pointer to open file (Note 3).
240
241			returns - 0 on success, TM_E_* on failure.
242			*/
243
244			extern int
245			tmMapPicture(BYTE *psp, int xp, int *yp, int flags,
246			RGBPRIMP monpri, double gamval, double Lddyn, double Ldmax,
247			char fname, FILE fp);
248			/*
249			Load and apply tone mapping to Radiance picture.
250			Stack is restored to its original state upon return.
251			If fp is TM_GETFILE and (flags&TM_F_UNIMPL)!=0, tmMapPicture()
252			calls pcond to perform the actual conversion, which takes
253			longer but gives access to all the TM_F_* features.
254	greg	3.5	Memory for the final pixel array is allocated using malloc(3),
255			and should be freed with free(3) when it is no longer needed.
256	greg	3.1
257	gwlarson	3.9	psp - returned array of tone mapped pixels, picture ordering.
258	greg	3.1	xp, yp - returned picture dimensions.
259			flags - TM_F_* flags indicating what is to be done.
260			monpri - display monitor primaries (Note 1).
261			gamval - display gamma response.
262			Lddyn - the display's dynamic range (0. for default).
263			Ldmax - maximum display luminance in cd/m^2 (0. for default).
264			fname - picture file name.
265			fp - pointer to open file (Note 3).
266
267			returns - 0 on success, TM_E_* on failure.
268			*/
269
270			extern struct tmStruct *
271			tmPop(void);
272			/*
273			Pops current tone mapping from stack.
274
275			returns - pointer to tone mapping structure, or NULL if none.
276			*/
277
278			extern int
279			tmPull(struct tmStruct *tms);
280			/*
281			Pull tone mapping from anywhere in stack.
282
283			tms - tone mapping structure to find.
284
285			returns - 1 if found in stack, 0 otherwise.
286			*/
287
288			extern int
289			tmPush(struct tmStruct *tms);
290			/*
291			Make tone mapping active by (pulling it and) pushing it to the top.
292
293			tms - initialized tone mapping structure.
294
295			returns - 0 on success, TM_E_* if tms is invalid.
296			*/
297
298	greg	3.3	extern struct tmStruct *
299			tmDup(void);
300			/*
301			Duplicate the current tone mapping into a new structure on the stack.
302
303			returns - pointer to new top, or NULL on error.
304			*/
305
306	greg	3.1	extern void
307			tmDone(struct tmStruct *tms);
308			/*
309			Free data associated with the given tone mapping structure.
310			Calls tmPull() first to remove it from the stack if present.
311			The calls tmDone(tmPop()), tmDone(tmTop) and tmDone(NULL)
312			all have the same effect, which is to remove and free
313			the current tone mapping.
314
315			tms - tone mapping structure to free.
316			*/
317
318			#endif
319	greg	3.4
320
321	greg	3.1	/** Notes **/
322			/*
323			General:
324
325			The usual sequence after calling tmInit() is to convert some
326			pixel values to chroma and luminance encodings, which can
327			be passed to tmAddHisto() to put into the tone mapping histogram.
328			This histogram is then used along with the display parameters
329	greg	3.5	by tmComputeMapping() to compute the luminance mapping function.
330	greg	3.1	(Colors are tone-mapped as they are converted if TM_F_MESOPIC
331			is set.) The encoded chroma and luminance values may then be
332			passed to tmMapPixels() to apply the computed tone mapping in
333			a second pass.
334
335			Especially for RGBE colors in the same color space as the
336			target display, the conversion to chroma and luminance values
337			is fast enough that it may be recomputed on the second pass
338			if memory is at a premium. (Since the chroma values are only
339			used during final mapping, setting the cs parameter to TM_NOCHROM
340			on the first pass will save time.) Another memory saving option
341			if third and subsequent passes are not needed is to use the
342	greg	3.3	same array to store the mapped pixels as used to store
343	greg	3.1	the encoded chroma values. This way, only two extra bytes
344			for storing encoded luminances are required per pixel. This
345			is the method employed by tmMapPicture(), for example.
346			*/
347			/*
348			Note 1:
349
350			All RGBPRIMP values should be pointers to static structures.
351			I.e., the same pointer should be used for the same primaries,
352			and those primaries should not change from one call to the next.
353			This is because the routines use the pointer value to identify
354			computed conversion matrices, so the matrices do not have to be
355			rebuilt each time. If you are using the standard primaries,
356			use the standard primary pointer, stdprims.
357
358			To indicate a set of input primaries are actually CIE XYZ,
359			the TM_XYZPRIM macro may be passed. If the input primaries
360			are unknown, it is wisest to pass tmTop->monpri to tmSetSpace().
361			By default, the input primaries equal the monitor primaries
362			and the scalefactor is set to WHTEFFICACY in tmInit().
363			*/
364			/*
365			Note 2:
366
367			Chrominance is optional in most of these routines, whether
368			TM_F_BW is set or not. Passing a value of TM_NOCHROM (or
369			TM_NOCHROMP for picture reading) indicates that returned
370			color values are not desired.
371
372			If TM_NOCHROM is passed to a mapping routine expecting chroma
373			input, it will do without it and return luminance channel
374			rather than RGB pixel values. Otherwise, the array for
375			returned pixel values may be the same array used to pass
376			encoded chrominances if no other mappings are desired.
377			*/
378			/*
379			Note 3:
380
381			Picture files may either be opened by the calling routine or by
382			the library function. If opened by the calling routine, the
383			pointer to the stream is passed, which may be a pipe or other
384			non-seekable input as it is only read once. It must be
385			positioned at the beginning when the function is called, and it
386			will be positioned at the end on return. It will not be closed.
387			If the passed stream pointer is TM_GETFILE, then the library
388			function will open the file, read its contents and close it
389			before returning, whether or not an error was encountered.
390			*/