src/px/neuclrtab.c

#ifndef lint
static const char       RCSid[] = "$Id$";
#endif
/*
 * Neural-Net quantization algorithm based on work of Anthony Dekker
 */

#include "standard.h"

#include "color.h"

#include "random.h"

#ifdef COMPAT_MODE
#define neu_init        new_histo
#define neu_pixel       cnt_pixel
#define neu_colrs       cnt_colrs
#define neu_clrtab      new_clrtab
#define neu_map_pixel   map_pixel
#define neu_map_colrs   map_colrs
#define neu_dith_colrs  dith_colrs
#endif
                                /* our color table (global) */
extern BYTE     clrtab[256][3];
static int      clrtabsiz;

#ifndef DEFSMPFAC
#ifdef SPEED
#define DEFSMPFAC       (240/SPEED+3)
#else
#define DEFSMPFAC       30
#endif
#endif

int     samplefac = DEFSMPFAC;  /* sampling factor */

                /* Samples array starts off holding spacing between adjacent
                 * samples, and ends up holding actual BGR sample values.
                 */
static BYTE     *thesamples;
static int      nsamples;
static BYTE     *cursamp;
static long     skipcount;

#define MAXSKIP         (1<<24-1)

#define nskip(sp)       ((long)(sp)[0]<<16|(long)(sp)[1]<<8|(long)(sp)[2])

#define setskip(sp,n)   ((sp)[0]=(n)>>16,(sp)[1]=((n)>>8)&255,(sp)[2]=(n)&255)

static  cpyclrtab();


neu_init(npixels)               /* initialize our sample array */
long    npixels;
{
        register int    nsleft;
        register long   sv;
        double  rval, cumprob;
        long    npleft;

        nsamples = npixels/samplefac;
        if (nsamples < 600)
                return(-1);
        thesamples = (BYTE *)malloc(nsamples*3);
        if (thesamples == NULL)
                return(-1);
        cursamp = thesamples;
        npleft = npixels;
        nsleft = nsamples;
        while (nsleft) {
                rval = frandom();       /* random distance to next sample */
                sv = 0;
                cumprob = 0.;
                while ((cumprob += (1.-cumprob)*nsleft/(npleft-sv)) < rval)
                        sv++;
                if (nsleft == nsamples)
                        skipcount = sv;
                else {
                        setskip(cursamp, sv);
                        cursamp += 3;
                }
                npleft -= sv+1;
                nsleft--;
        }
        setskip(cursamp, npleft);       /* tag on end to skip the rest */
        cursamp = thesamples;
        return(0);
}


neu_pixel(col)                  /* add pixel to our samples */
register BYTE   col[];
{
        if (!skipcount--) {
                skipcount = nskip(cursamp);
                cursamp[0] = col[BLU];
                cursamp[1] = col[GRN];
                cursamp[2] = col[RED];
                cursamp += 3;
        }
}


neu_colrs(cs, n)                /* add a scanline to our samples */
register COLR   *cs;
register int    n;
{
        while (n > skipcount) {
                cs += skipcount;
                n -= skipcount+1;
                skipcount = nskip(cursamp);
                cursamp[0] = cs[0][BLU];
                cursamp[1] = cs[0][GRN];
                cursamp[2] = cs[0][RED];
                cs++;
                cursamp += 3;
        }
        skipcount -= n;
}


neu_clrtab(ncolors)             /* make new color table using ncolors */
int     ncolors;
{
        clrtabsiz = ncolors;
        if (clrtabsiz > 256) clrtabsiz = 256;
        initnet();
        learn();
        unbiasnet();
        cpyclrtab();
        inxbuild();
                                /* we're done with our samples */
        free((void *)thesamples);
                                /* reset dithering function */
        neu_dith_colrs((BYTE *)NULL, (COLR *)NULL, 0);
                                /* return new color table size */
        return(clrtabsiz);
}


int
neu_map_pixel(col)              /* get pixel for color */
register BYTE   col[];
{
        return(inxsearch(col[BLU],col[GRN],col[RED]));
}


neu_map_colrs(bs, cs, n)        /* convert a scanline to color index values */
register BYTE   *bs;
register COLR   *cs;
register int    n;
{
        while (n-- > 0) {
                *bs++ = inxsearch(cs[0][BLU],cs[0][GRN],cs[0][RED]);
                cs++;
        }
}


neu_dith_colrs(bs, cs, n)       /* convert scanline to dithered index values */
register BYTE   *bs;
register COLR   *cs;
int     n;
{
        static short    (*cerr)[3] = NULL;
        static int      N = 0;
        int     err[3], errp[3];
        register int    x, i;

        if (n != N) {           /* get error propogation array */
                if (N) {
                        free((void *)cerr);
                        cerr = NULL;
                }
                if (n)
                        cerr = (short (*)[3])malloc(3*n*sizeof(short));
                if (cerr == NULL) {
                        N = 0;
                        map_colrs(bs, cs, n);
                        return;
                }
                N = n;
                bzero((char *)cerr, 3*N*sizeof(short));
        }
        err[0] = err[1] = err[2] = 0;
        for (x = 0; x < n; x++) {
                for (i = 0; i < 3; i++) {       /* dither value */
                        errp[i] = err[i];
                        err[i] += cerr[x][i];
#ifdef MAXERR
                        if (err[i] > MAXERR) err[i] = MAXERR;
                        else if (err[i] < -MAXERR) err[i] = -MAXERR;
#endif
                        err[i] += cs[x][i];
                        if (err[i] < 0) err[i] = 0;
                        else if (err[i] > 255) err[i] = 255;
                }
                bs[x] = inxsearch(err[BLU],err[GRN],err[RED]);
                for (i = 0; i < 3; i++) {       /* propagate error */
                        err[i] -= clrtab[bs[x]][i];
                        err[i] /= 3;
                        cerr[x][i] = err[i] + errp[i];
                }
        }
}

/* The following was adapted and modified from the original (GW)        */

/* cheater definitions (GW) */
#define thepicture      thesamples
#define lengthcount     (nsamples*3)
#define samplefac       1

/*----------------------------------------------------------------------*/
/*                                                                      */
/*                              NeuQuant                                */
/*                              --------                                */
/*                                                                      */
/*              Copyright: Anthony Dekker, November 1994                */
/*                                                                      */
/* This program performs colour quantization of graphics images (SUN    */
/* raster files).  It uses a Kohonen Neural Network.  It produces       */
/* better results than existing methods and runs faster, using minimal  */
/* space (8kB plus the image itself).  The algorithm is described in    */
/* the paper "Kohonen Neural Networks for Optimal Colour Quantization"  */
/* to appear in the journal "Network: Computation in Neural Systems".   */
/* It is a significant improvement of an earlier algorithm.             */
/*                                                                      */
/* This program is distributed free for academic use or for evaluation  */
/* by commercial organizations.                                         */
/*                                                                      */
/*      Usage:  NeuQuant -n inputfile > outputfile                      */
/*                                                                      */
/* where n is a sampling factor for neural learning.                    */
/*                                                                      */
/* Program performance compared with other methods is as follows:       */
/*                                                                      */
/*      Algorithm               |  Av. CPU Time |  Quantization Error   */
/*      -------------------------------------------------------------   */
/*      NeuQuant -3             |  314          |  5.55                 */
/*      NeuQuant -10            |  119          |  5.97                 */
/*      NeuQuant -30            |  65           |  6.53                 */
/*      Oct-Trees               |  141          |  8.96                 */
/*      Median Cut (XV -best)   |  420          |  9.28                 */
/*      Median Cut (XV -slow)   |  72           |  12.15                */
/*                                                                      */
/* Author's address:    Dept of ISCS, National University of Singapore  */
/*                      Kent Ridge, Singapore 0511                      */
/* Email:       [email protected]                                     */
/*----------------------------------------------------------------------*/

#define bool            int
#define false           0
#define true            1

/* network defs */
#define netsize         clrtabsiz               /* number of colours - can change this */
#define maxnetpos       (netsize-1)
#define netbiasshift    4                       /* bias for colour values */
#define ncycles         100                     /* no. of learning cycles */

/* defs for freq and bias */
#define intbiasshift    16                      /* bias for fractions */
#define intbias         (((int) 1)<<intbiasshift)
#define gammashift      10                      /* gamma = 1024 */
#define gamma           (((int) 1)<<gammashift)
#define betashift       10
#define beta            (intbias>>betashift)    /* beta = 1/1024 */
#define betagamma       (intbias<<(gammashift-betashift))

/* defs for decreasing radius factor */
#define initrad         (256>>3)                /* for 256 cols, radius starts */
#define radiusbiasshift 6                       /* at 32.0 biased by 6 bits */
#define radiusbias      (((int) 1)<<radiusbiasshift)
#define initradius      (initrad*radiusbias)    /* and decreases by a */
#define radiusdec       30                      /* factor of 1/30 each cycle */ 

/* defs for decreasing alpha factor */
#define alphabiasshift  10                      /* alpha starts at 1.0 */
#define initalpha       (((int) 1)<<alphabiasshift)
int alphadec;                                   /* biased by 10 bits */

/* radbias and alpharadbias used for radpower calculation */
#define radbiasshift    8
#define radbias         (((int) 1)<<radbiasshift)
#define alpharadbshift  (alphabiasshift+radbiasshift)
#define alpharadbias    (((int) 1)<<alpharadbshift)

/* four primes near 500 - assume no image has a length so large */
/* that it is divisible by all four primes */
#define prime1          499
#define prime2          491
#define prime3          487
#define prime4          503

typedef int pixel[4];  /* BGRc */
pixel network[256];

int netindex[256];      /* for network lookup - really 256 */

int bias [256];         /* bias and freq arrays for learning */
int freq [256];
int radpower[initrad];  /* radpower for precomputation */


/* initialise network in range (0,0,0) to (255,255,255) */

initnet()       
{
        register int i;
        register int *p;
        
        for (i=0; i<netsize; i++) {
                p = network[i];
                p[0] = p[1] = p[2] = (i << (netbiasshift+8))/netsize;
                freq[i] = intbias/netsize;  /* 1/netsize */
                bias[i] = 0;
        }
}


/* do after unbias - insertion sort of network and build netindex[0..255] */

inxbuild()
{
        register int i,j,smallpos,smallval;
        register int *p,*q;
        int previouscol,startpos;

        previouscol = 0;
        startpos = 0;
        for (i=0; i<netsize; i++) {
                p = network[i];
                smallpos = i;
                smallval = p[1];        /* index on g */
                /* find smallest in i..netsize-1 */
                for (j=i+1; j<netsize; j++) {
                        q = network[j];
                        if (q[1] < smallval) {  /* index on g */
                                smallpos = j;
                                smallval = q[1]; /* index on g */
                        }
                }
                q = network[smallpos];
                /* swap p (i) and q (smallpos) entries */
                if (i != smallpos) {
                        j = q[0];   q[0] = p[0];   p[0] = j;
                        j = q[1];   q[1] = p[1];   p[1] = j;
                        j = q[2];   q[2] = p[2];   p[2] = j;
                        j = q[3];   q[3] = p[3];   p[3] = j;
                }
                /* smallval entry is now in position i */
                if (smallval != previouscol) {
                        netindex[previouscol] = (startpos+i)>>1;
                        for (j=previouscol+1; j<smallval; j++) netindex[j] = i;
                        previouscol = smallval;
                        startpos = i;
                }
        }
        netindex[previouscol] = (startpos+maxnetpos)>>1;
        for (j=previouscol+1; j<256; j++) netindex[j] = maxnetpos; /* really 256 */
}


int inxsearch(b,g,r)  /* accepts real BGR values after net is unbiased */
register int b,g,r;
{
        register int i,j,dist,a,bestd;
        register int *p;
        int best;

        bestd = 1000;   /* biggest possible dist is 256*3 */
        best = -1;
        i = netindex[g]; /* index on g */
        j = i-1;         /* start at netindex[g] and work outwards */

        while ((i<netsize) || (j>=0)) {
                if (i<netsize) {
                        p = network[i];
                        dist = p[1] - g;        /* inx key */
                        if (dist >= bestd) i = netsize; /* stop iter */
                        else {
                                i++;
                                if (dist<0) dist = -dist;
                                a = p[0] - b;   if (a<0) a = -a;
                                dist += a;
                                if (dist<bestd) {
                                        a = p[2] - r;   if (a<0) a = -a;
                                        dist += a;
                                        if (dist<bestd) {bestd=dist; best=p[3];}
                                }
                        }
                }
                if (j>=0) {
                        p = network[j];
                        dist = g - p[1]; /* inx key - reverse dif */
                        if (dist >= bestd) j = -1; /* stop iter */
                        else {
                                j--;
                                if (dist<0) dist = -dist;
                                a = p[0] - b;   if (a<0) a = -a;
                                dist += a;
                                if (dist<bestd) {
                                        a = p[2] - r;   if (a<0) a = -a;
                                        dist += a;
                                        if (dist<bestd) {bestd=dist; best=p[3];}
                                }
                        }
                }
        }
        return(best);
}


/* finds closest neuron (min dist) and updates freq */
/* finds best neuron (min dist-bias) and returns position */
/* for frequently chosen neurons, freq[i] is high and bias[i] is negative */
/* bias[i] = gamma*((1/netsize)-freq[i]) */

int contest(b,g,r)      /* accepts biased BGR values */
register int b,g,r;
{
        register int i,dist,a,biasdist,betafreq;
        int bestpos,bestbiaspos,bestd,bestbiasd;
        register int *p,*f, *n;

        bestd = ~(((int) 1)<<31);
        bestbiasd = bestd;
        bestpos = -1;
        bestbiaspos = bestpos;
        p = bias;
        f = freq;

        for (i=0; i<netsize; i++) {
                n = network[i];
                dist = n[0] - b;   if (dist<0) dist = -dist;
                a = n[1] - g;   if (a<0) a = -a;
                dist += a;
                a = n[2] - r;   if (a<0) a = -a;
                dist += a;
                if (dist<bestd) {bestd=dist; bestpos=i;}
                biasdist = dist - ((*p)>>(intbiasshift-netbiasshift));
                if (biasdist<bestbiasd) {bestbiasd=biasdist; bestbiaspos=i;}
                betafreq = (*f >> betashift);
                *f++ -= betafreq;
                *p++ += (betafreq<<gammashift);
        }
        freq[bestpos] += beta;
        bias[bestpos] -= betagamma;
        return(bestbiaspos);
}


/* move neuron i towards (b,g,r) by factor alpha */

altersingle(alpha,i,b,g,r)      /* accepts biased BGR values */
register int alpha,i,b,g,r;
{
        register int *n;

        n = network[i];         /* alter hit neuron */
        *n -= (alpha*(*n - b)) / initalpha;
        n++;
        *n -= (alpha*(*n - g)) / initalpha;
        n++;
        *n -= (alpha*(*n - r)) / initalpha;
}


/* move neurons adjacent to i towards (b,g,r) by factor */
/* alpha*(1-((i-j)^2/[r]^2)) precomputed as radpower[|i-j|]*/

alterneigh(rad,i,b,g,r) /* accents biased BGR values */
int rad,i;
register int b,g,r;
{
        register int j,k,lo,hi,a;
        register int *p, *q;

        lo = i-rad;   if (lo<-1) lo= -1;
        hi = i+rad;   if (hi>netsize) hi=netsize;

        j = i+1;
        k = i-1;
        q = radpower;
        while ((j<hi) || (k>lo)) {
                a = (*(++q));
                if (j<hi) {
                        p = network[j];
                        *p -= (a*(*p - b)) / alpharadbias;
                        p++;
                        *p -= (a*(*p - g)) / alpharadbias;
                        p++;
                        *p -= (a*(*p - r)) / alpharadbias;
                        j++;
                }
                if (k>lo) {
                        p = network[k];
                        *p -= (a*(*p - b)) / alpharadbias;
                        p++;
                        *p -= (a*(*p - g)) / alpharadbias;
                        p++;
                        *p -= (a*(*p - r)) / alpharadbias;
                        k--;
                }
        }
}


learn()
{
        register int i,j,b,g,r;
        int radius,rad,alpha,step,delta,samplepixels;
        register unsigned char *p;
        unsigned char *lim;

        alphadec = 30 + ((samplefac-1)/3);
        p = thepicture;
        lim = thepicture + lengthcount;
        samplepixels = lengthcount/(3*samplefac);
        delta = samplepixels/ncycles;
        alpha = initalpha;
        radius = initradius;
        
        rad = radius >> radiusbiasshift;
        if (rad <= 1) rad = 0;
        for (i=0; i<rad; i++) 
                radpower[i] = alpha*(((rad*rad - i*i)*radbias)/(rad*rad));
        
        if ((lengthcount%prime1) != 0) step = 3*prime1;
        else {
                if ((lengthcount%prime2) !=0) step = 3*prime2;
                else {
                        if ((lengthcount%prime3) !=0) step = 3*prime3;
                        else step = 3*prime4;
                }
        }
        
        i = 0;
        while (i < samplepixels) {
                b = p[0] << netbiasshift;
                g = p[1] << netbiasshift;
                r = p[2] << netbiasshift;
                j = contest(b,g,r);

                altersingle(alpha,j,b,g,r);
                if (rad) alterneigh(rad,j,b,g,r);   /* alter neighbours */

                p += step;
                if (p >= lim) p -= lengthcount;
        
                i++;
                if (i%delta == 0) {     
                        alpha -= alpha / alphadec;
                        radius -= radius / radiusdec;
                        rad = radius >> radiusbiasshift;
                        if (rad <= 1) rad = 0;
                        for (j=0; j<rad; j++) 
                                radpower[j] = alpha*(((rad*rad - j*j)*radbias)/(rad*rad));
                }
        }
}
        
/* unbias network to give 0..255 entries */
/* which can then be used for colour map */
/* and record position i to prepare for sort */

unbiasnet()
{
        int i,j;

        for (i=0; i<netsize; i++) {
                for (j=0; j<3; j++)
                        network[i][j] >>= netbiasshift;
                network[i][3] = i; /* record colour no */
        }
}


/* Don't do this until the network has been unbiased (GW) */
                
static
cpyclrtab()
{
        register int i,j,k;
        
        for (j=0; j<netsize; j++) {
                k = network[j][3];
                for (i = 0; i < 3; i++)
                        clrtab[k][i] = network[j][2-i];
        }
}
Revision:	2.9
Committed:	Sat Feb 22 02:07:27 2003 UTC (22 years, 8 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad3R5
Changes since 2.8:	+3 -6 lines
Log Message:	Changes and check-in for 3.5 release Includes new source files and modifications not recorded for many years See ray/doc/notes/ReleaseNotes for notes between 3.1 and 3.5 release
#	User	Rev	Content
1	greg	2.1	#ifndef lint
2	greg	2.9	static const char RCSid[] = "$Id$";
3	greg	2.1	#endif
4			/*
5			* Neural-Net quantization algorithm based on work of Anthony Dekker
6			*/
7
8			#include "standard.h"
9
10			#include "color.h"
11
12			#include "random.h"
13
14			#ifdef COMPAT_MODE
15			#define neu_init new_histo
16			#define neu_pixel cnt_pixel
17			#define neu_colrs cnt_colrs
18			#define neu_clrtab new_clrtab
19			#define neu_map_pixel map_pixel
20			#define neu_map_colrs map_colrs
21			#define neu_dith_colrs dith_colrs
22			#endif
23			/* our color table (global) */
24			extern BYTE clrtab[256][3];
25			static int clrtabsiz;
26
27			#ifndef DEFSMPFAC
28			#ifdef SPEED
29			#define DEFSMPFAC (240/SPEED+3)
30			#else
31			#define DEFSMPFAC 30
32			#endif
33			#endif
34
35			int samplefac = DEFSMPFAC; /* sampling factor */
36
37			/* Samples array starts off holding spacing between adjacent
38			* samples, and ends up holding actual BGR sample values.
39			*/
40			static BYTE *thesamples;
41			static int nsamples;
42			static BYTE *cursamp;
43			static long skipcount;
44
45			#define MAXSKIP (1<<24-1)
46
47			#define nskip(sp) ((long)(sp)[0]<<16\|(long)(sp)[1]<<8\|(long)(sp)[2])
48
49			#define setskip(sp,n) ((sp)[0]=(n)>>16,(sp)[1]=((n)>>8)&255,(sp)[2]=(n)&255)
50
51	greg	2.8	static cpyclrtab();
52
53	greg	2.1
54			neu_init(npixels) /* initialize our sample array */
55			long npixels;
56			{
57			register int nsleft;
58			register long sv;
59			double rval, cumprob;
60			long npleft;
61
62			nsamples = npixels/samplefac;
63			if (nsamples < 600)
64			return(-1);
65	greg	2.2	thesamples = (BYTE )malloc(nsamples3);
66	greg	2.1	if (thesamples == NULL)
67			return(-1);
68			cursamp = thesamples;
69			npleft = npixels;
70			nsleft = nsamples;
71			while (nsleft) {
72			rval = frandom(); /* random distance to next sample */
73			sv = 0;
74			cumprob = 0.;
75			while ((cumprob += (1.-cumprob)*nsleft/(npleft-sv)) < rval)
76			sv++;
77	greg	2.2	if (nsleft == nsamples)
78			skipcount = sv;
79			else {
80			setskip(cursamp, sv);
81			cursamp += 3;
82			}
83			npleft -= sv+1;
84	greg	2.1	nsleft--;
85			}
86	greg	2.2	setskip(cursamp, npleft); /* tag on end to skip the rest */
87	greg	2.1	cursamp = thesamples;
88			return(0);
89			}
90
91
92			neu_pixel(col) /* add pixel to our samples */
93			register BYTE col[];
94			{
95			if (!skipcount--) {
96	greg	2.2	skipcount = nskip(cursamp);
97	greg	2.1	cursamp[0] = col[BLU];
98			cursamp[1] = col[GRN];
99			cursamp[2] = col[RED];
100			cursamp += 3;
101			}
102			}
103
104
105			neu_colrs(cs, n) /* add a scanline to our samples */
106			register COLR *cs;
107			register int n;
108			{
109			while (n > skipcount) {
110			cs += skipcount;
111	greg	2.2	n -= skipcount+1;
112			skipcount = nskip(cursamp);
113	greg	2.1	cursamp[0] = cs[0][BLU];
114			cursamp[1] = cs[0][GRN];
115			cursamp[2] = cs[0][RED];
116			cs++;
117			cursamp += 3;
118			}
119			skipcount -= n;
120			}
121
122
123			neu_clrtab(ncolors) /* make new color table using ncolors */
124			int ncolors;
125			{
126			clrtabsiz = ncolors;
127			if (clrtabsiz > 256) clrtabsiz = 256;
128			initnet();
129			learn();
130			unbiasnet();
131			cpyclrtab();
132			inxbuild();
133			/* we're done with our samples */
134	greg	2.9	free((void *)thesamples);
135	greg	2.1	/* reset dithering function */
136			neu_dith_colrs((BYTE )NULL, (COLR )NULL, 0);
137			/* return new color table size */
138			return(clrtabsiz);
139			}
140
141
142			int
143			neu_map_pixel(col) /* get pixel for color */
144			register BYTE col[];
145			{
146			return(inxsearch(col[BLU],col[GRN],col[RED]));
147			}
148
149
150			neu_map_colrs(bs, cs, n) /* convert a scanline to color index values */
151			register BYTE *bs;
152			register COLR *cs;
153			register int n;
154			{
155			while (n-- > 0) {
156			*bs++ = inxsearch(cs[0][BLU],cs[0][GRN],cs[0][RED]);
157			cs++;
158			}
159			}
160
161
162			neu_dith_colrs(bs, cs, n) /* convert scanline to dithered index values */
163			register BYTE *bs;
164			register COLR *cs;
165			int n;
166			{
167			static short (*cerr)[3] = NULL;
168			static int N = 0;
169			int err[3], errp[3];
170			register int x, i;
171
172			if (n != N) { /* get error propogation array */
173			if (N) {
174	greg	2.9	free((void *)cerr);
175	greg	2.1	cerr = NULL;
176			}
177			if (n)
178			cerr = (short ()[3])malloc(3n*sizeof(short));
179			if (cerr == NULL) {
180			N = 0;
181			map_colrs(bs, cs, n);
182			return;
183			}
184			N = n;
185			bzero((char )cerr, 3N*sizeof(short));
186			}
187			err[0] = err[1] = err[2] = 0;
188			for (x = 0; x < n; x++) {
189			for (i = 0; i < 3; i++) { /* dither value */
190			errp[i] = err[i];
191			err[i] += cerr[x][i];
192			#ifdef MAXERR
193			if (err[i] > MAXERR) err[i] = MAXERR;
194			else if (err[i] < -MAXERR) err[i] = -MAXERR;
195			#endif
196			err[i] += cs[x][i];
197			if (err[i] < 0) err[i] = 0;
198			else if (err[i] > 255) err[i] = 255;
199			}
200			bs[x] = inxsearch(err[BLU],err[GRN],err[RED]);
201			for (i = 0; i < 3; i++) { /* propagate error */
202			err[i] -= clrtab[bs[x]][i];
203			err[i] /= 3;
204			cerr[x][i] = err[i] + errp[i];
205			}
206			}
207			}
208
209			/* The following was adapted and modified from the original (GW) */
210	greg	2.6
211			/* cheater definitions (GW) */
212			#define thepicture thesamples
213			#define lengthcount (nsamples*3)
214			#define samplefac 1
215
216	greg	2.1	/----------------------------------------------------------------------/
217			/* */
218			/* NeuQuant */
219			/* -------- */
220			/* */
221	greg	2.6	/* Copyright: Anthony Dekker, November 1994 */
222	greg	2.1	/* */
223			/* This program performs colour quantization of graphics images (SUN */
224			/* raster files). It uses a Kohonen Neural Network. It produces */
225			/* better results than existing methods and runs faster, using minimal */
226			/* space (8kB plus the image itself). The algorithm is described in */
227			/* the paper "Kohonen Neural Networks for Optimal Colour Quantization" */
228			/* to appear in the journal "Network: Computation in Neural Systems". */
229			/* It is a significant improvement of an earlier algorithm. */
230			/* */
231			/* This program is distributed free for academic use or for evaluation */
232			/* by commercial organizations. */
233			/* */
234			/* Usage: NeuQuant -n inputfile > outputfile */
235			/* */
236			/* where n is a sampling factor for neural learning. */
237			/* */
238			/* Program performance compared with other methods is as follows: */
239			/* */
240			/* Algorithm \| Av. CPU Time \| Quantization Error */
241			/* ------------------------------------------------------------- */
242			/* NeuQuant -3 \| 314 \| 5.55 */
243			/* NeuQuant -10 \| 119 \| 5.97 */
244			/* NeuQuant -30 \| 65 \| 6.53 */
245			/* Oct-Trees \| 141 \| 8.96 */
246			/* Median Cut (XV -best) \| 420 \| 9.28 */
247			/* Median Cut (XV -slow) \| 72 \| 12.15 */
248			/* */
249			/* Author's address: Dept of ISCS, National University of Singapore */
250			/* Kent Ridge, Singapore 0511 */
251			/* Email: [email protected] */
252			/----------------------------------------------------------------------/
253
254	greg	2.6	#define bool int
255			#define false 0
256			#define true 1
257	greg	2.1
258	greg	2.6	/* network defs */
259	greg	2.7	#define netsize clrtabsiz /* number of colours - can change this */
260	greg	2.6	#define maxnetpos (netsize-1)
261			#define netbiasshift 4 /* bias for colour values */
262			#define ncycles 100 /* no. of learning cycles */
263	greg	2.1
264			/* defs for freq and bias */
265	greg	2.6	#define intbiasshift 16 /* bias for fractions */
266			#define intbias (((int) 1)<<intbiasshift)
267			#define gammashift 10 /* gamma = 1024 */
268			#define gamma (((int) 1)<<gammashift)
269			#define betashift 10
270			#define beta (intbias>>betashift) /* beta = 1/1024 */
271	greg	2.1	#define betagamma (intbias<<(gammashift-betashift))
272
273	greg	2.6	/* defs for decreasing radius factor */
274	greg	2.7	#define initrad (256>>3) /* for 256 cols, radius starts */
275	greg	2.6	#define radiusbiasshift 6 /* at 32.0 biased by 6 bits */
276			#define radiusbias (((int) 1)<<radiusbiasshift)
277			#define initradius (initradradiusbias) / and decreases by a */
278			#define radiusdec 30 /* factor of 1/30 each cycle */
279
280			/* defs for decreasing alpha factor */
281			#define alphabiasshift 10 /* alpha starts at 1.0 */
282			#define initalpha (((int) 1)<<alphabiasshift)
283			int alphadec; /* biased by 10 bits */
284
285			/* radbias and alpharadbias used for radpower calculation */
286	greg	2.1	#define radbiasshift 8
287	greg	2.6	#define radbias (((int) 1)<<radbiasshift)
288	greg	2.1	#define alpharadbshift (alphabiasshift+radbiasshift)
289	greg	2.6	#define alpharadbias (((int) 1)<<alpharadbshift)
290	greg	2.1
291	greg	2.6	/* four primes near 500 - assume no image has a length so large */
292			/* that it is divisible by all four primes */
293			#define prime1 499
294			#define prime2 491
295			#define prime3 487
296			#define prime4 503
297	greg	2.1
298			typedef int pixel[4]; /* BGRc */
299	greg	2.7	pixel network[256];
300	greg	2.1
301	greg	2.6	int netindex[256]; /* for network lookup - really 256 */
302	greg	2.1
303	greg	2.7	int bias [256]; /* bias and freq arrays for learning */
304			int freq [256];
305	greg	2.6	int radpower[initrad]; /* radpower for precomputation */
306	greg	2.1
307
308	greg	2.6	/* initialise network in range (0,0,0) to (255,255,255) */
309	greg	2.1
310	greg	2.6	initnet()
311	greg	2.1	{
312			register int i;
313			register int *p;
314
315	greg	2.7	for (i=0; i<netsize; i++) {
316	greg	2.1	p = network[i];
317	greg	2.7	p[0] = p[1] = p[2] = (i << (netbiasshift+8))/netsize;
318			freq[i] = intbias/netsize; /* 1/netsize */
319	greg	2.1	bias[i] = 0;
320			}
321			}
322
323
324	greg	2.6	/* do after unbias - insertion sort of network and build netindex[0..255] */
325
326	greg	2.1	inxbuild()
327			{
328			register int i,j,smallpos,smallval;
329			register int p,q;
330	greg	2.6	int previouscol,startpos;
331	greg	2.1
332	greg	2.6	previouscol = 0;
333			startpos = 0;
334	greg	2.7	for (i=0; i<netsize; i++) {
335	greg	2.1	p = network[i];
336			smallpos = i;
337			smallval = p[1]; /* index on g */
338	greg	2.7	/* find smallest in i..netsize-1 */
339			for (j=i+1; j<netsize; j++) {
340	greg	2.1	q = network[j];
341			if (q[1] < smallval) { /* index on g */
342			smallpos = j;
343			smallval = q[1]; /* index on g */
344			}
345			}
346			q = network[smallpos];
347	greg	2.6	/* swap p (i) and q (smallpos) entries */
348	greg	2.1	if (i != smallpos) {
349			j = q[0]; q[0] = p[0]; p[0] = j;
350			j = q[1]; q[1] = p[1]; p[1] = j;
351			j = q[2]; q[2] = p[2]; p[2] = j;
352			j = q[3]; q[3] = p[3]; p[3] = j;
353			}
354			/* smallval entry is now in position i */
355	greg	2.6	if (smallval != previouscol) {
356			netindex[previouscol] = (startpos+i)>>1;
357			for (j=previouscol+1; j<smallval; j++) netindex[j] = i;
358			previouscol = smallval;
359			startpos = i;
360	greg	2.1	}
361			}
362	greg	2.6	netindex[previouscol] = (startpos+maxnetpos)>>1;
363			for (j=previouscol+1; j<256; j++) netindex[j] = maxnetpos; /* really 256 */
364	greg	2.1	}
365
366
367	greg	2.6	int inxsearch(b,g,r) /* accepts real BGR values after net is unbiased */
368	greg	2.1	register int b,g,r;
369			{
370	greg	2.6	register int i,j,dist,a,bestd;
371	greg	2.1	register int *p;
372	greg	2.6	int best;
373	greg	2.1
374			bestd = 1000; /* biggest possible dist is 2563 /
375			best = -1;
376			i = netindex[g]; /* index on g */
377	greg	2.6	j = i-1; /* start at netindex[g] and work outwards */
378	greg	2.1
379	greg	2.7	while ((i<netsize) \|\| (j>=0)) {
380			if (i<netsize) {
381	greg	2.1	p = network[i];
382	greg	2.6	dist = p[1] - g; /* inx key */
383	greg	2.7	if (dist >= bestd) i = netsize; /* stop iter */
384	greg	2.1	else {
385			i++;
386	greg	2.6	if (dist<0) dist = -dist;
387			a = p[0] - b; if (a<0) a = -a;
388			dist += a;
389			if (dist<bestd) {
390			a = p[2] - r; if (a<0) a = -a;
391			dist += a;
392			if (dist<bestd) {bestd=dist; best=p[3];}
393	greg	2.1	}
394			}
395			}
396			if (j>=0) {
397			p = network[j];
398	greg	2.6	dist = g - p[1]; /* inx key - reverse dif */
399			if (dist >= bestd) j = -1; /* stop iter */
400	greg	2.1	else {
401			j--;
402	greg	2.6	if (dist<0) dist = -dist;
403			a = p[0] - b; if (a<0) a = -a;
404			dist += a;
405			if (dist<bestd) {
406			a = p[2] - r; if (a<0) a = -a;
407			dist += a;
408			if (dist<bestd) {bestd=dist; best=p[3];}
409	greg	2.1	}
410			}
411			}
412			}
413			return(best);
414			}
415
416
417	greg	2.6	/* finds closest neuron (min dist) and updates freq */
418			/* finds best neuron (min dist-bias) and returns position */
419			/* for frequently chosen neurons, freq[i] is high and bias[i] is negative */
420	greg	2.7	/* bias[i] = gamma((1/netsize)-freq[i]) /
421	greg	2.6
422			int contest(b,g,r) /* accepts biased BGR values */
423	greg	2.1	register int b,g,r;
424			{
425	greg	2.6	register int i,dist,a,biasdist,betafreq;
426			int bestpos,bestbiaspos,bestd,bestbiasd;
427			register int p,f, *n;
428	greg	2.1
429	greg	2.6	bestd = ~(((int) 1)<<31);
430	greg	2.1	bestbiasd = bestd;
431	greg	2.6	bestpos = -1;
432			bestbiaspos = bestpos;
433			p = bias;
434			f = freq;
435
436	greg	2.7	for (i=0; i<netsize; i++) {
437	greg	2.6	n = network[i];
438			dist = n[0] - b; if (dist<0) dist = -dist;
439			a = n[1] - g; if (a<0) a = -a;
440			dist += a;
441			a = n[2] - r; if (a<0) a = -a;
442			dist += a;
443			if (dist<bestd) {bestd=dist; bestpos=i;}
444			biasdist = dist - ((*p)>>(intbiasshift-netbiasshift));
445			if (biasdist<bestbiasd) {bestbiasd=biasdist; bestbiaspos=i;}
446			betafreq = (*f >> betashift);
447			*f++ -= betafreq;
448			*p++ += (betafreq<<gammashift);
449	greg	2.1	}
450	greg	2.6	freq[bestpos] += beta;
451			bias[bestpos] -= betagamma;
452			return(bestbiaspos);
453	greg	2.1	}
454
455
456	greg	2.6	/* move neuron i towards (b,g,r) by factor alpha */
457
458			altersingle(alpha,i,b,g,r) /* accepts biased BGR values */
459			register int alpha,i,b,g,r;
460			{
461			register int *n;
462
463			n = network[i]; /* alter hit neuron */
464			n -= (alpha(*n - b)) / initalpha;
465			n++;
466			n -= (alpha(*n - g)) / initalpha;
467			n++;
468			n -= (alpha(*n - r)) / initalpha;
469			}
470
471
472			/* move neurons adjacent to i towards (b,g,r) by factor */
473			/* alpha(1-((i-j)^2/[r]^2)) precomputed as radpower[\|i-j\|]/
474
475			alterneigh(rad,i,b,g,r) /* accents biased BGR values */
476	greg	2.1	int rad,i;
477			register int b,g,r;
478			{
479			register int j,k,lo,hi,a;
480			register int p, q;
481
482	greg	2.6	lo = i-rad; if (lo<-1) lo= -1;
483	greg	2.7	hi = i+rad; if (hi>netsize) hi=netsize;
484	greg	2.1
485			j = i+1;
486			k = i-1;
487			q = radpower;
488			while ((j<hi) \|\| (k>lo)) {
489			a = (*(++q));
490			if (j<hi) {
491			p = network[j];
492			p -= (a(*p - b)) / alpharadbias;
493			p++;
494			p -= (a(*p - g)) / alpharadbias;
495			p++;
496			p -= (a(*p - r)) / alpharadbias;
497			j++;
498			}
499			if (k>lo) {
500			p = network[k];
501			p -= (a(*p - b)) / alpharadbias;
502			p++;
503			p -= (a(*p - g)) / alpharadbias;
504			p++;
505			p -= (a(*p - r)) / alpharadbias;
506			k--;
507			}
508			}
509			}
510
511
512			learn()
513			{
514			register int i,j,b,g,r;
515	greg	2.6	int radius,rad,alpha,step,delta,samplepixels;
516	greg	2.1	register unsigned char *p;
517			unsigned char *lim;
518
519	greg	2.6	alphadec = 30 + ((samplefac-1)/3);
520			p = thepicture;
521	greg	2.1	lim = thepicture + lengthcount;
522	greg	2.6	samplepixels = lengthcount/(3*samplefac);
523			delta = samplepixels/ncycles;
524	greg	2.1	alpha = initalpha;
525			radius = initradius;
526	greg	2.6
527	greg	2.1	rad = radius >> radiusbiasshift;
528			if (rad <= 1) rad = 0;
529			for (i=0; i<rad; i++)
530			radpower[i] = alpha(((radrad - ii)radbias)/(rad*rad));
531	greg	2.6
532			if ((lengthcount%prime1) != 0) step = 3*prime1;
533	greg	2.1	else {
534	greg	2.6	if ((lengthcount%prime2) !=0) step = 3*prime2;
535	greg	2.1	else {
536	greg	2.6	if ((lengthcount%prime3) !=0) step = 3*prime3;
537			else step = 3*prime4;
538	greg	2.1	}
539			}
540	greg	2.6
541	greg	2.1	i = 0;
542	greg	2.6	while (i < samplepixels) {
543	greg	2.1	b = p[0] << netbiasshift;
544			g = p[1] << netbiasshift;
545			r = p[2] << netbiasshift;
546			j = contest(b,g,r);
547
548			altersingle(alpha,j,b,g,r);
549	greg	2.6	if (rad) alterneigh(rad,j,b,g,r); /* alter neighbours */
550	greg	2.1
551			p += step;
552			if (p >= lim) p -= lengthcount;
553
554			i++;
555			if (i%delta == 0) {
556			alpha -= alpha / alphadec;
557			radius -= radius / radiusdec;
558			rad = radius >> radiusbiasshift;
559			if (rad <= 1) rad = 0;
560			for (j=0; j<rad; j++)
561			radpower[j] = alpha(((radrad - jj)radbias)/(rad*rad));
562			}
563			}
564			}
565
566	greg	2.6	/* unbias network to give 0..255 entries */
567			/* which can then be used for colour map */
568			/* and record position i to prepare for sort */
569
570	greg	2.1	unbiasnet()
571			{
572			int i,j;
573
574	greg	2.7	for (i=0; i<netsize; i++) {
575	greg	2.1	for (j=0; j<3; j++)
576			network[i][j] >>= netbiasshift;
577			network[i][3] = i; /* record colour no */
578			}
579			}
580
581	greg	2.6
582			/* Don't do this until the network has been unbiased (GW) */
583	greg	2.1
584			static
585			cpyclrtab()
586			{
587			register int i,j,k;
588
589	greg	2.7	for (j=0; j<netsize; j++) {
590	greg	2.1	k = network[j][3];
591			for (i = 0; i < 3; i++)
592			clrtab[k][i] = network[j][2-i];
593			}
594			}