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xv24to8.c
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xv24to8.c
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/*
* xv24to8.c - contains the 24-to-8-bit Conv24to8() procedure
* and the 8-to-24-bit Conv8to24() procedure
*
* The Conv24to8 procedure takes a pointer to a 24-bit image (loaded
* previously). The image will be a w * h * 3 byte array of
* bytes. The image will be arranged with 3 bytes per pixel (in order
* R, G, and B), pixel 0 at the top left corner. (As normal.)
* The procedure also takes a maximum number of colors to use (numcols)
* and pointers to three 256-long arrays of bytes (to hold the returned
* colormap)
*
* Note that Conv24to8() does NOT free the pic24 image under any circumstances
*
* The Conv24to8 procedure will set up the following: it will allocate, make
* & return 'pic8', a 'w' by 'h' (passed in values) 8-bit picture.
* it will load up the rmap, gmap and bmap colormap arrays. it will NOT
* calculate numcols, since the cmap sort procedure has to be called anyway
*
* Conv24to8 returns 'pic8' if successful, 'NULL' on failure (presumably on a
* malloc())
*
* The 'slow' code, while still based on Heckbert's Median Cut algorithm,
* has been shamelessly lifted from the Independent JPEG Group's software
* (jquant2.c), as (for a variety of reasons) theirs was far better than
* the version I was previously using. Thanks guys!
*
* Also, as is my way, I've stripped out most of the IJG's well-written
* comments regarding their algorithm. Folks interested in learning how it
* works are encouraged to look at the original source. (jpeg/jquant2.c)
*
* contains:
* Cont24to8()
* Init24to8()
*/
#include "copyright.h"
/*
* Portions Copyright (C) 1989, 1991 by Jef Poskanzer. See copyright notice
* below, at the beginning of the relevant code.
*/
#include "xv.h"
static int quick_check PARM((byte*, int,int, byte*, byte*,byte*,byte*,int));
static int quick_quant PARM((byte*, int,int, byte*, byte*,byte*,byte*,int));
static int ppm_quant PARM((byte *,int,int, byte*, byte*,byte*,byte*,int));
static int slow_quant PARM((byte*, int,int, byte*, byte*,byte*,byte*,int));
/****************************/
void Init24to8()
{
/* doesn't do anything anymore... */
}
/****************************/
byte *Conv24to8(pic24,w,h,nc,rm,gm,bm)
byte *pic24;
byte *rm, *gm, *bm;
int w,h,nc;
{
/* returns pointer to new 8-bit-per-pixel image (w*h) if successful, or
NULL if unsuccessful */
int i;
byte *pic8;
if (!pic24) return NULL;
pic8 = (byte *) malloc((size_t) (w * h));
if (!pic8) {
fprintf(stderr,"%s: Conv24to8() - failed to allocate 'pic8'\n",cmd);
return pic8;
}
if (nc<=0) nc = 255; /* 'nc == 0' breaks code */
if (!noqcheck && quick_check(pic24, w,h, pic8, rm,gm,bm, nc)) {
SetISTR(ISTR_INFO,"No color compression was necessary.\n");
return pic8;
}
switch (conv24) {
case CONV24_FAST:
SetISTR(ISTR_INFO,"Doing 'quick' 24-bit to 8-bit conversion.");
i = quick_quant(pic24, w, h, pic8, rm, gm, bm, nc);
break;
case CONV24_BEST:
SetISTR(ISTR_INFO,"Doing 'best' 24-bit to 8-bit conversion.");
i = ppm_quant(pic24, w, h, pic8, rm, gm, bm, nc);
break;
case CONV24_SLOW:
default:
SetISTR(ISTR_INFO,"Doing 'slow' 24-bit to 8-bit conversion.");
i = slow_quant(pic24, w, h, pic8, rm, gm, bm, nc);
break;
}
if (i) { free(pic8); pic8 = NULL; }
return pic8;
}
/***************************************************************/
byte *Conv8to24(pic8, w, h, rmap,gmap,bmap)
byte *pic8, *rmap, *gmap, *bmap;
int w, h;
{
/* converts an w*h 8-bit image (with colormap rmap,gmap,bmap) into a
* 24-bit image. Note, 'pic8' could be NULL
*
* returns pointer to new 24-bits-per-pixel image (w*h) if successful,
* or NULL if unsuccessful
*/
int i;
byte *pic24, *sp, *dp;
pic24 = (byte *) malloc((size_t) (w * h * 3));
if (!pic24) return pic24;
for (i=w*h, sp=pic8, dp=pic24; i; i--, sp++) {
if ((i&0x1ffff)==0) WaitCursor();
*dp++ = rmap[*sp];
*dp++ = gmap[*sp];
*dp++ = bmap[*sp];
}
return pic24;
}
/****************************/
static int quick_check(pic24, w,h, pic8, rmap,gmap,bmap, maxcol)
byte *pic24, *pic8, *rmap, *gmap, *bmap;
int w,h,maxcol;
{
/* scans picture until it finds more than 'maxcol' different colors. If it
finds more than 'maxcol' colors, it returns '0'. If it DOESN'T, it does
the 24-to-8 conversion by simply sticking the colors it found into
a colormap, and changing instances of a color in pic24 into colormap
indicies (in pic8) */
unsigned long colors[256],col;
int i, nc, low, high, mid;
byte *p, *pix;
if (maxcol>256) maxcol = 256;
/* put the first color in the table by hand */
nc = 0; mid = 0;
for (i=w*h,p=pic24; i; i--) {
col = (((u_long) *p++) << 16);
col += (((u_long) *p++) << 8);
col += *p++;
/* binary search the 'colors' array to see if it's in there */
low = 0; high = nc-1;
while (low <= high) {
mid = (low+high)/2;
if (col < colors[mid]) high = mid - 1;
else if (col > colors[mid]) low = mid + 1;
else break;
}
if (high < low) { /* didn't find color in list, add it. */
if (nc>=maxcol) return 0;
xvbcopy((char *) &colors[low], (char *) &colors[low+1],
(nc - low) * sizeof(u_long));
colors[low] = col;
nc++;
}
}
/* run through the data a second time, this time mapping pixel values in
pic24 into colormap offsets into 'colors' */
for (i=w*h,p=pic24, pix=pic8; i; i--,pix++) {
col = (((u_long) *p++) << 16);
col += (((u_long) *p++) << 8);
col += *p++;
/* binary search the 'colors' array. It *IS* in there */
low = 0; high = nc-1;
while (low <= high) {
mid = (low+high)/2;
if (col < colors[mid]) high = mid - 1;
else if (col > colors[mid]) low = mid + 1;
else break;
}
if (high < low) {
fprintf(stderr,"quick_check: impossible situation!\n");
exit(1);
}
*pix = mid;
}
/* and load up the 'desired colormap' */
for (i=0; i<nc; i++) {
rmap[i] = colors[i]>>16;
gmap[i] = (colors[i]>>8) & 0xff;
bmap[i] = colors[i] & 0xff;
}
return 1;
}
/************************************/
static int quick_quant(p24,w,h, p8, rmap,gmap,bmap, nc)
byte *p24, *p8, *rmap, *gmap, *bmap;
int w,h,nc;
{
/* called after 'pic8' has been alloced, pWIDE,pHIGH set up, mono/1-bit
checked already */
/* up to 256 colors: 3 bits R, 3 bits G, 2 bits B (RRRGGGBB) */
#define RMASK 0xe0
#define RSHIFT 0
#define GMASK 0xe0
#define GSHIFT 3
#define BMASK 0xc0
#define BSHIFT 6
byte *pp;
int r1, g1, b1;
int *thisline, *nextline, *thisptr, *nextptr, *tmpptr;
int i, j, val, pwide3;
int imax, jmax;
pp = p8; pwide3 = w * 3; imax = h-1; jmax = w-1;
/* load up colormap:
* note that 0 and 255 of each color are always in the map;
* intermediate values are evenly spaced.
*/
for (i=0; i<256; i++) {
rmap[i] = (((i<<RSHIFT) & RMASK) * 255 + RMASK/2) / RMASK;
gmap[i] = (((i<<GSHIFT) & GMASK) * 255 + GMASK/2) / GMASK;
bmap[i] = (((i<<BSHIFT) & BMASK) * 255 + BMASK/2) / BMASK;
}
thisline = (int *) malloc(pwide3 * sizeof(int));
nextline = (int *) malloc(pwide3 * sizeof(int));
if (!thisline || !nextline) {
if (thisline) free(thisline);
if (nextline) free(nextline);
fprintf(stderr,"%s: unable to allocate memory in quick_quant()\n", cmd);
return(1);
}
/* get first line of picture */
for (j=pwide3, tmpptr=nextline; j; j--) *tmpptr++ = (int) *p24++;
for (i=0; i<h; i++) {
tmpptr = thisline; thisline = nextline; nextline = tmpptr; /* swap */
if ((i&0x3f) == 0) WaitCursor();
if (i!=imax) /* get next line */
for (j=pwide3, tmpptr=nextline; j; j--)
*tmpptr++ = (int) *p24++;
for (j=0, thisptr=thisline, nextptr=nextline; j<w; j++,pp++) {
r1 = *thisptr++; g1 = *thisptr++; b1 = *thisptr++;
RANGE(r1,0,255); RANGE(g1,0,255); RANGE(b1,0,255);
/* choose actual pixel value */
val = (((r1&RMASK)>>RSHIFT) | ((g1&GMASK)>>GSHIFT) |
((b1&BMASK)>>BSHIFT));
*pp = val;
/* compute color errors */
r1 -= rmap[val];
g1 -= gmap[val];
b1 -= bmap[val];
/* Add fractions of errors to adjacent pixels */
if (j!=jmax) { /* adjust RIGHT pixel */
thisptr[0] += (r1*7) / 16;
thisptr[1] += (g1*7) / 16;
thisptr[2] += (b1*7) / 16;
}
if (i!=imax) { /* do BOTTOM pixel */
nextptr[0] += (r1*5) / 16;
nextptr[1] += (g1*5) / 16;
nextptr[2] += (b1*5) / 16;
if (j>0) { /* do BOTTOM LEFT pixel */
nextptr[-3] += (r1*3) / 16;
nextptr[-2] += (g1*3) / 16;
nextptr[-1] += (b1*3) / 16;
}
if (j!=jmax) { /* do BOTTOM RIGHT pixel */
nextptr[3] += (r1)/16;
nextptr[4] += (g1)/16;
nextptr[5] += (b1)/16;
}
nextptr += 3;
}
}
}
free(thisline);
free(nextline);
return 0;
#undef RMASK
#undef RSHIFT
#undef GMASK
#undef GSHIFT
#undef BMASK
#undef BSHIFT
}
/***************************************************************/
/* The following code based on code from the 'pbmplus' package */
/* written by Jef Poskanzer */
/***************************************************************/
/* ppmquant.c - quantize the colors in a pixmap down to a specified number
**
** Copyright (C) 1989, 1991 by Jef Poskanzer.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation. This software is provided "as is" without express or
** implied warranty.
*/
typedef unsigned char pixval;
#define PPM_MAXMAXVAL 255
typedef struct { pixval r, g, b; } pixel;
#define PPM_GETR(p) ((p).r)
#define PPM_GETG(p) ((p).g)
#define PPM_GETB(p) ((p).b)
#define PPM_ASSIGN(p,red,grn,blu) \
{ (p).r = (red); (p).g = (grn); (p).b = (blu); }
#define PPM_EQUAL(p,q) ( (p).r == (q).r && (p).g == (q).g && (p).b == (q).b )
/* Color scaling macro -- to make writing ppmtowhatever easier. */
#define PPM_DEPTH(newp,p,oldmaxval,newmaxval) \
PPM_ASSIGN( (newp), \
((int) PPM_GETR(p)) * ((int)newmaxval) / ((int)oldmaxval), \
((int) PPM_GETG(p)) * ((int)newmaxval) / ((int)oldmaxval), \
((int) PPM_GETB(p)) * ((int)newmaxval) / ((int)oldmaxval) )
/* Luminance macro. */
/*
* #define PPM_LUMIN(p) \
* ( 0.299 * PPM_GETR(p) + 0.587 * PPM_GETG(p) + 0.114 * PPM_GETB(p) )
*/
/* Luminance macro, using only integer ops. Returns an int (*256) JHB */
#define PPM_LUMIN(p) \
( 77 * PPM_GETR(p) + 150 * PPM_GETG(p) + 29 * PPM_GETB(p) )
/* Color histogram stuff. */
typedef struct chist_item* chist_vec;
struct chist_item { pixel color;
int value;
};
typedef struct chist_list_item* chist_list;
struct chist_list_item { struct chist_item ch;
chist_list next;
};
typedef chist_list* chash_table;
typedef struct box* box_vector;
struct box {
int index;
int colors;
int sum;
};
#define MAXCOLORS 32767
#define CLUSTER_MAXVAL 63
#define LARGE_LUM
#define REP_AVERAGE_PIXELS
#define FS_SCALE 1024
#define HASH_SIZE 6553
#define ppm_hashpixel(p) ((((int) PPM_GETR(p) * 33023 + \
(int) PPM_GETG(p) * 30013 + \
(int) PPM_GETB(p) * 27011) & 0x7fffffff) \
% HASH_SIZE)
/*** function defs ***/
static chist_vec mediancut PARM((chist_vec, int, int, int, int));
static int redcompare PARM((const void *, const void *));
static int greencompare PARM((const void *, const void *));
static int bluecompare PARM((const void *, const void *));
static int sumcompare PARM((const void *, const void *));
static chist_vec ppm_computechist PARM((pixel **, int,int,int,int *));
static chash_table ppm_computechash PARM((pixel **, int,int,int,int *));
static chist_vec ppm_chashtochist PARM((chash_table, int));
static chash_table ppm_allocchash PARM((void));
static void ppm_freechist PARM((chist_vec));
static void ppm_freechash PARM((chash_table));
/****************************************************************************/
static int ppm_quant(pic24, cols, rows, pic8, rmap, gmap, bmap, newcolors)
byte *pic24, *pic8, *rmap, *gmap, *bmap;
int cols, rows, newcolors;
{
pixel** pixels;
register pixel* pP;
int row;
register int col, limitcol;
pixval maxval, newmaxval;
int colors;
register int index;
chist_vec chv, colormap;
chash_table cht;
int i;
unsigned char *picptr;
static const char *fn = "ppmquant()";
index = 0;
maxval = 255;
/*
* reformat 24-bit pic24 image (3 bytes per pixel) into 2-dimensional
* array of pixel structures
*/
if (DEBUG) fprintf(stderr,"%s: remapping to ppm-style internal fmt\n", fn);
WaitCursor();
pixels = (pixel **) malloc(rows * sizeof(pixel *));
if (!pixels) FatalError("couldn't allocate 'pixels' array");
for (row=0; row<rows; row++) {
pixels[row] = (pixel *) malloc(cols * sizeof(pixel));
if (!pixels[row]) FatalError("couldn't allocate a row of pixels array");
for (col=0, pP=pixels[row]; col<cols; col++, pP++) {
pP->r = *pic24++;
pP->g = *pic24++;
pP->b = *pic24++;
}
}
if (DEBUG) fprintf(stderr,"%s: done format remapping\n", fn);
/*
* attempt to make a histogram of the colors, unclustered.
* If at first we don't succeed, lower maxval to increase color
* coherence and try again. This will eventually terminate, with
* maxval at worst 15, since 32^3 is approximately MAXCOLORS.
*/
WaitCursor();
for ( ; ; ) {
if (DEBUG) fprintf(stderr, "%s: making histogram\n", fn);
chv = ppm_computechist(pixels, cols, rows, MAXCOLORS, &colors);
if (chv != (chist_vec) 0) break;
if (DEBUG) fprintf(stderr, "%s: too many colors!\n", fn);
newmaxval = maxval / 2;
if (DEBUG) fprintf(stderr, "%s: rescaling colors (maxval=%d) %s\n",
fn, newmaxval, "to improve clustering");
for (row=0; row<rows; ++row)
for (col=0, pP=pixels[row]; col<cols; ++col, ++pP)
PPM_DEPTH( *pP, *pP, maxval, newmaxval );
maxval = newmaxval;
}
if (DEBUG) fprintf(stderr,"%s: %d colors found\n", fn, colors);
/*
* Step 3: apply median-cut to histogram, making the new colormap.
*/
WaitCursor();
if (DEBUG) fprintf(stderr, "%s: choosing %d colors\n", fn, newcolors);
colormap = mediancut(chv, colors, rows * cols, maxval, newcolors);
ppm_freechist(chv);
/*
* Step 4: map the colors in the image to their closest match in the
* new colormap, and write 'em out.
*/
if (DEBUG) fprintf(stderr,"%s: mapping image to new colors\n", fn);
cht = ppm_allocchash();
picptr = pic8;
for (row = 0; row < rows; ++row) {
col = 0; limitcol = cols; pP = pixels[row];
ProgressMeter(0, rows-1, row, "24 -> 8");
if ((row & 0x1f) == 0) WaitCursor();
do {
int hash;
chist_list chl;
/* Check hash table to see if we have already matched this color. */
hash = ppm_hashpixel(*pP);
for (chl = cht[hash]; chl; chl = chl->next)
if (PPM_EQUAL(chl->ch.color, *pP)) {index = chl->ch.value; break;}
if (!chl /*index = -1*/) {/* No; search colormap for closest match. */
register int i, r1, g1, b1, r2, g2, b2;
register long dist, newdist;
r1 = PPM_GETR( *pP );
g1 = PPM_GETG( *pP );
b1 = PPM_GETB( *pP );
dist = 2000000000;
for (i=0; i<newcolors; i++) {
r2 = PPM_GETR( colormap[i].color );
g2 = PPM_GETG( colormap[i].color );
b2 = PPM_GETB( colormap[i].color );
newdist = ( r1 - r2 ) * ( r1 - r2 ) +
( g1 - g2 ) * ( g1 - g2 ) +
( b1 - b2 ) * ( b1 - b2 );
if (newdist<dist) { index = i; dist = newdist; }
}
hash = ppm_hashpixel(*pP);
chl = (chist_list) malloc(sizeof(struct chist_list_item));
if (!chl) FatalError("ran out of memory adding to hash table");
chl->ch.color = *pP;
chl->ch.value = index;
chl->next = cht[hash];
cht[hash] = chl;
}
*picptr++ = index;
++col;
++pP;
}
while (col != limitcol);
}
/* rescale the colormap and load the XV colormap */
for (i=0; i<newcolors; i++) {
PPM_DEPTH(colormap[i].color, colormap[i].color, maxval, 255);
rmap[i] = PPM_GETR( colormap[i].color );
gmap[i] = PPM_GETG( colormap[i].color );
bmap[i] = PPM_GETB( colormap[i].color );
}
/* free the pixels array */
for (i=0; i<rows; i++) free(pixels[i]);
free(pixels);
/* free cht and colormap */
ppm_freechist(colormap);
ppm_freechash(cht);
return 0;
}
/*
** Here is the fun part, the median-cut colormap generator. This is based
** on Paul Heckbert's paper "Color Image Quantization for Frame Buffer
** Display", SIGGRAPH '82 Proceedings, page 297.
*/
/****************************************************************************/
static chist_vec mediancut( chv, colors, sum, maxval, newcolors )
chist_vec chv;
int colors, sum, newcolors;
int maxval;
{
chist_vec colormap;
box_vector bv;
register int bi, i;
int boxes;
bv = (box_vector) malloc(sizeof(struct box) * newcolors);
colormap = (chist_vec)
malloc(sizeof(struct chist_item) * newcolors );
if (!bv || !colormap) FatalError("unable to malloc in mediancut()");
for (i=0; i<newcolors; i++)
PPM_ASSIGN(colormap[i].color, 0, 0, 0);
/*
* Set up the initial box.
*/
bv[0].index = 0;
bv[0].colors = colors;
bv[0].sum = sum;
boxes = 1;
/*
** Main loop: split boxes until we have enough.
*/
while ( boxes < newcolors ) {
register int indx, clrs;
int sm;
register int minr, maxr, ming, maxg, minb, maxb, v;
int halfsum, lowersum;
/*
** Find the first splittable box.
*/
for (bi=0; bv[bi].colors<2 && bi<boxes; bi++) ;
if (bi == boxes) break; /* ran out of colors! */
indx = bv[bi].index;
clrs = bv[bi].colors;
sm = bv[bi].sum;
/*
** Go through the box finding the minimum and maximum of each
** component - the boundaries of the box.
*/
minr = maxr = PPM_GETR( chv[indx].color );
ming = maxg = PPM_GETG( chv[indx].color );
minb = maxb = PPM_GETB( chv[indx].color );
for (i=1; i<clrs; i++) {
v = PPM_GETR( chv[indx + i].color );
if (v < minr) minr = v;
if (v > maxr) maxr = v;
v = PPM_GETG( chv[indx + i].color );
if (v < ming) ming = v;
if (v > maxg) maxg = v;
v = PPM_GETB( chv[indx + i].color );
if (v < minb) minb = v;
if (v > maxb) maxb = v;
}
/*
** Find the largest dimension, and sort by that component. I have
** included two methods for determining the "largest" dimension;
** first by simply comparing the range in RGB space, and second
** by transforming into luminosities before the comparison. You
** can switch which method is used by switching the commenting on
** the LARGE_ defines at the beginning of this source file.
*/
{
/* LARGE_LUM version */
pixel p;
int rl, gl, bl;
PPM_ASSIGN(p, maxr - minr, 0, 0);
rl = PPM_LUMIN(p);
PPM_ASSIGN(p, 0, maxg - ming, 0);
gl = PPM_LUMIN(p);
PPM_ASSIGN(p, 0, 0, maxb - minb);
bl = PPM_LUMIN(p);
if (rl >= gl && rl >= bl)
qsort((char*) &(chv[indx]), (size_t) clrs, sizeof(struct chist_item),
redcompare );
else if (gl >= bl)
qsort((char*) &(chv[indx]), (size_t) clrs, sizeof(struct chist_item),
greencompare );
else
qsort((char*) &(chv[indx]), (size_t) clrs, sizeof(struct chist_item),
bluecompare );
}
/*
** Now find the median based on the counts, so that about half the
** pixels (not colors, pixels) are in each subdivision.
*/
lowersum = chv[indx].value;
halfsum = sm / 2;
for (i=1; i<clrs-1; i++) {
if (lowersum >= halfsum) break;
lowersum += chv[indx + i].value;
}
/*
** Split the box, and sort to bring the biggest boxes to the top.
*/
bv[bi].colors = i;
bv[bi].sum = lowersum;
bv[boxes].index = indx + i;
bv[boxes].colors = clrs - i;
bv[boxes].sum = sm - lowersum;
++boxes;
qsort((char*) bv, (size_t) boxes, sizeof(struct box), sumcompare);
} /* while (boxes ... */
/*
** Ok, we've got enough boxes. Now choose a representative color for
** each box. There are a number of possible ways to make this choice.
** One would be to choose the center of the box; this ignores any structure
** within the boxes. Another method would be to average all the colors in
** the box - this is the method specified in Heckbert's paper. A third
** method is to average all the pixels in the box. You can switch which
** method is used by switching the commenting on the REP_ defines at
** the beginning of this source file.
*/
for (bi=0; bi<boxes; bi++) {
/* REP_AVERAGE_PIXELS version */
register int indx = bv[bi].index;
register int clrs = bv[bi].colors;
register long r = 0, g = 0, b = 0, sum = 0;
for (i=0; i<clrs; i++) {
r += PPM_GETR( chv[indx + i].color ) * chv[indx + i].value;
g += PPM_GETG( chv[indx + i].color ) * chv[indx + i].value;
b += PPM_GETB( chv[indx + i].color ) * chv[indx + i].value;
sum += chv[indx + i].value;
}
r = r / sum; if (r>maxval) r = maxval; /* avoid math errors */
g = g / sum; if (g>maxval) g = maxval;
b = b / sum; if (b>maxval) b = maxval;
PPM_ASSIGN( colormap[bi].color, r, g, b );
}
free(bv);
return colormap;
}
/**********************************/
static int redcompare(p1, p2)
const void *p1, *p2;
{
return (int) PPM_GETR( ((chist_vec)p1)->color ) -
(int) PPM_GETR( ((chist_vec)p2)->color );
}
/**********************************/
static int greencompare(p1, p2)
const void *p1, *p2;
{
return (int) PPM_GETG( ((chist_vec)p1)->color ) -
(int) PPM_GETG( ((chist_vec)p2)->color );
}
/**********************************/
static int bluecompare(p1, p2)
const void *p1, *p2;
{
return (int) PPM_GETB( ((chist_vec)p1)->color ) -
(int) PPM_GETB( ((chist_vec)p2)->color );
}
/**********************************/
static int sumcompare(p1, p2)
const void *p1, *p2;
{
return ((box_vector) p2)->sum - ((box_vector) p1)->sum;
}
/****************************************************************************/
static chist_vec
ppm_computechist(pixels, cols, rows, maxcolors, colorsP)
pixel** pixels;
int cols, rows, maxcolors;
int* colorsP;
{
chash_table cht;
chist_vec chv;
cht = ppm_computechash(pixels, cols, rows, maxcolors, colorsP);
if (!cht) return (chist_vec) 0;
chv = ppm_chashtochist(cht, maxcolors);
ppm_freechash(cht);
return chv;
}
/****************************************************************************/
static chash_table ppm_computechash(pixels, cols, rows,
maxcolors, colorsP )
pixel** pixels;
int cols, rows, maxcolors;
int* colorsP;
{
chash_table cht;
register pixel* pP;
chist_list chl;
int col, row, hash;
cht = ppm_allocchash( );
*colorsP = 0;
/* Go through the entire image, building a hash table of colors. */
for (row=0; row<rows; row++)
for (col=0, pP=pixels[row]; col<cols; col++, pP++) {
hash = ppm_hashpixel(*pP);
for (chl = cht[hash]; chl != (chist_list) 0; chl = chl->next)
if (PPM_EQUAL(chl->ch.color, *pP)) break;
if (chl != (chist_list) 0) ++(chl->ch.value);
else {
if ((*colorsP)++ > maxcolors) {
ppm_freechash(cht);
return (chash_table) 0;
}
chl = (chist_list) malloc(sizeof(struct chist_list_item));
if (!chl) FatalError("ran out of memory computing hash table");
chl->ch.color = *pP;
chl->ch.value = 1;
chl->next = cht[hash];
cht[hash] = chl;
}
}
return cht;
}
/****************************************************************************/
static chash_table ppm_allocchash()
{
chash_table cht;
int i;
cht = (chash_table) malloc( HASH_SIZE * sizeof(chist_list) );
if (!cht) FatalError("ran out of memory allocating hash table");
for (i=0; i<HASH_SIZE; i++ )
cht[i] = (chist_list) 0;
return cht;
}
/****************************************************************************/
static chist_vec ppm_chashtochist( cht, maxcolors )
chash_table cht;
int maxcolors;
{
chist_vec chv;
chist_list chl;
int i, j;
/* Now collate the hash table into a simple chist array. */
chv = (chist_vec) malloc( maxcolors * sizeof(struct chist_item) );
/* (Leave room for expansion by caller.) */
if (!chv) FatalError("ran out of memory generating histogram");
/* Loop through the hash table. */
j = 0;
for (i=0; i<HASH_SIZE; i++)
for (chl = cht[i]; chl != (chist_list) 0; chl = chl->next) {
/* Add the new entry. */
chv[j] = chl->ch;
++j;
}
return chv;
}
/****************************************************************************/
static void ppm_freechist( chv )
chist_vec chv;
{
free( (char*) chv );
}
/****************************************************************************/
static void ppm_freechash( cht )
chash_table cht;
{
int i;
chist_list chl, chlnext;
for (i=0; i<HASH_SIZE; i++)
for (chl = cht[i]; chl != (chist_list) 0; chl = chlnext) {
chlnext = chl->next;
free( (char*) chl );
}
free( (char*) cht );
}
/***************************************************************/
/* The following is based on jquant2.c from version 5 */
/* of the IJG JPEG software, which is */
/* Copyright (C) 1991-1994, Thomas G. Lane. */
/***************************************************************/
#define MAXNUMCOLORS 256 /* maximum size of colormap */
#define C0_SCALE 2 /* scale R distances by this much */
#define C1_SCALE 3 /* scale G distances by this much */
#define C2_SCALE 1 /* and B by this much */
#define HIST_C0_BITS 5 /* bits of precision in R histogram */
#define HIST_C1_BITS 6 /* bits of precision in G histogram */
#define HIST_C2_BITS 5 /* bits of precision in B histogram */
/* Number of elements along histogram axes. */
#define HIST_C0_ELEMS (1<<HIST_C0_BITS)
#define HIST_C1_ELEMS (1<<HIST_C1_BITS)
#define HIST_C2_ELEMS (1<<HIST_C2_BITS)
/* These are the amounts to shift an input value to get a histogram index. */
#define C0_SHIFT (8-HIST_C0_BITS)
#define C1_SHIFT (8-HIST_C1_BITS)
#define C2_SHIFT (8-HIST_C2_BITS)
typedef unsigned char JSAMPLE;
typedef JSAMPLE * JSAMPROW;
typedef u_short histcell; /* histogram cell; prefer an unsigned type */
typedef histcell * histptr; /* for pointers to histogram cells */
typedef histcell hist1d[HIST_C2_ELEMS]; /* typedefs for the histogram array */
typedef hist1d hist2d[HIST_C1_ELEMS];
typedef hist2d hist3d[HIST_C0_ELEMS];
typedef short FSERROR; /* 16 bits should be enough */
typedef int LOCFSERROR; /* use 'int' for calculation temps */
typedef FSERROR *FSERRPTR; /* pointer to error array */