| 1 |
greg |
1.2 |
/* Copyright 1988 Regents of the University of California */ |
| 2 |
greg |
1.1 |
|
| 3 |
|
|
#ifndef lint |
| 4 |
|
|
static char SCCSid[] = "$SunId$ LBL"; |
| 5 |
|
|
#endif |
| 6 |
greg |
1.2 |
|
| 7 |
|
|
/* |
| 8 |
greg |
1.1 |
CLOSEST - nearest-color lookup by locally ordered search |
| 9 |
|
|
we use distance in rgb space as color metric |
| 10 |
|
|
|
| 11 |
|
|
fillbucket subroutine makes trimmed, sorted lists of |
| 12 |
|
|
possible closest colors to speed the closest searching. |
| 13 |
|
|
About 6 times faster than exhaustive. |
| 14 |
|
|
|
| 15 |
|
|
Paul Heckbert |
| 16 |
|
|
*/ |
| 17 |
|
|
|
| 18 |
|
|
#include "ciq.h" |
| 19 |
|
|
|
| 20 |
|
|
#define inf 3*256*256 |
| 21 |
ph |
1.3 |
#define key(r,g,b) (((r)&0xe0)<<1|((g)&0xe0)>>2|((b)&0xe0)>>5) |
| 22 |
|
|
/* 9-bit hash key: rrrgggbbb */ |
| 23 |
greg |
1.1 |
|
| 24 |
ph |
1.3 |
static struct thing {int mindist,pv;} space[512*257],*next,*bucket[512]; |
| 25 |
greg |
1.1 |
/* sorted lists of colors */ |
| 26 |
|
|
|
| 27 |
ph |
1.3 |
static int nfill,tests,calls; |
| 28 |
greg |
1.1 |
static char filled[512]; /* has bucket[key] been filled yet? */ |
| 29 |
|
|
static int sq[511]; |
| 30 |
|
|
|
| 31 |
ph |
1.3 |
initializeclosest() { /* reset the buckets */ |
| 32 |
greg |
1.1 |
int k; |
| 33 |
|
|
nfill = tests = calls = 0; |
| 34 |
|
|
for (k=0; k<512; k++) filled[k] = 0; |
| 35 |
|
|
next = space; |
| 36 |
|
|
} |
| 37 |
|
|
|
| 38 |
|
|
closest(r,g,b) /* find pv of colormap color closest to (r,g,b) */ |
| 39 |
|
|
int r,g,b; |
| 40 |
|
|
{ |
| 41 |
|
|
register struct thing *p; |
| 42 |
ph |
1.3 |
register int *rsq,*gsq,*bsq,dist,min; |
| 43 |
|
|
int best,k; |
| 44 |
greg |
1.1 |
struct thing *p0; |
| 45 |
|
|
|
| 46 |
ph |
1.3 |
k = key(r,g,b); |
| 47 |
|
|
if (!filled[k]) fillbucket(k); |
| 48 |
greg |
1.1 |
min = inf; |
| 49 |
|
|
rsq = sq+255-r; |
| 50 |
|
|
gsq = sq+255-g; |
| 51 |
|
|
bsq = sq+255-b; |
| 52 |
|
|
|
| 53 |
|
|
/* stop looking when best is closer than next could be */ |
| 54 |
ph |
1.3 |
for (p0=p=bucket[k]; min>p->mindist; p++) { |
| 55 |
greg |
1.1 |
dist = rsq[color[0][p->pv]] + gsq[color[1][p->pv]] + |
| 56 |
|
|
bsq[color[2][p->pv]]; |
| 57 |
|
|
if (dist<min) { |
| 58 |
|
|
best = p->pv; |
| 59 |
|
|
min = dist; |
| 60 |
|
|
} |
| 61 |
|
|
} |
| 62 |
|
|
tests += p-p0; |
| 63 |
|
|
calls++; |
| 64 |
|
|
return best; |
| 65 |
|
|
} |
| 66 |
|
|
|
| 67 |
|
|
#define H 16 /* half-width of a bucket */ |
| 68 |
|
|
|
| 69 |
|
|
compare(a,b) |
| 70 |
|
|
register struct thing *a,*b; |
| 71 |
|
|
{ |
| 72 |
|
|
return a->mindist-b->mindist; |
| 73 |
|
|
} |
| 74 |
|
|
|
| 75 |
|
|
fillbucket(k) /* make list of colormap colors which could be closest */ |
| 76 |
|
|
int k; /* matches for colors in bucket #k */ |
| 77 |
|
|
{ |
| 78 |
|
|
register int r,g,b,j,dist,*rsq,*gsq,*bsq,min,best; |
| 79 |
|
|
struct thing *p,*q; |
| 80 |
|
|
|
| 81 |
|
|
if (!sq[0]) for (j= -255; j<256; j++) sq[j+255] = j*j; |
| 82 |
|
|
|
| 83 |
|
|
r = k>>1&0xe0|H; /* center of 32x32x32 cubical bucket */ |
| 84 |
|
|
g = k<<2&0xe0|H; |
| 85 |
|
|
b = k<<5&0xe0|H; |
| 86 |
|
|
rsq = sq+255-r; |
| 87 |
|
|
gsq = sq+255-g; |
| 88 |
|
|
bsq = sq+255-b; |
| 89 |
|
|
bucket[k] = p = next; |
| 90 |
|
|
min = inf; |
| 91 |
|
|
|
| 92 |
|
|
for (j=0; j<n; j++, p++) { |
| 93 |
|
|
p->pv = j; |
| 94 |
|
|
dist = 0; /* compute distance from cube surface */ |
| 95 |
|
|
if (color[0][j]< r-H) dist += rsq[color[0][j]+H]; |
| 96 |
|
|
else if (color[0][j]>=r+H) dist += rsq[color[0][j]-H+1]; |
| 97 |
|
|
if (color[1][j]< g-H) dist += gsq[color[1][j]+H]; |
| 98 |
|
|
else if (color[1][j]>=g+H) dist += gsq[color[1][j]-H+1]; |
| 99 |
|
|
if (color[2][j]< b-H) dist += bsq[color[2][j]+H]; |
| 100 |
|
|
else if (color[2][j]>=b+H) dist += bsq[color[2][j]-H+1]; |
| 101 |
|
|
p->mindist = dist; /* for termination test in closest */ |
| 102 |
|
|
dist = rsq[color[0][j]]+gsq[color[1][j]]+bsq[color[2][j]]; |
| 103 |
|
|
if (dist<min) { /* find color closest to cube center */ |
| 104 |
|
|
best = j; |
| 105 |
|
|
min = dist; |
| 106 |
|
|
} |
| 107 |
|
|
} |
| 108 |
|
|
|
| 109 |
|
|
dist = rsq[color[0][best]+(color[0][best]<r?1-H:H)] + |
| 110 |
|
|
gsq[color[1][best]+(color[1][best]<g?1-H:H)] + |
| 111 |
|
|
bsq[color[2][best]+(color[2][best]<b?1-H:H)]; |
| 112 |
|
|
/* dist is an upper bound on mindist: maximum possible distance */ |
| 113 |
|
|
/* between a color in the bucket and its nearest neighbor */ |
| 114 |
|
|
|
| 115 |
|
|
/* eliminate colors which couldn't be closest */ |
| 116 |
|
|
for (p=q=next, j=0; j<n; j++, p++) |
| 117 |
|
|
if (p->mindist<dist) { |
| 118 |
|
|
q->mindist = p->mindist; |
| 119 |
|
|
q->pv = p->pv; |
| 120 |
|
|
q++; |
| 121 |
|
|
} |
| 122 |
|
|
if (q<=next) fprintf(stderr,"ERROR: empty bucket!\n"); |
| 123 |
|
|
|
| 124 |
|
|
/* and sort the list by mindist */ |
| 125 |
|
|
qsort(next,q-next,sizeof(struct thing),compare); |
| 126 |
|
|
q->mindist = inf; /* list terminator */ |
| 127 |
|
|
next = q+1; |
| 128 |
|
|
filled[k] = 1; |
| 129 |
|
|
nfill++; |
| 130 |
|
|
} |
| 131 |
|
|
|
| 132 |
|
|
/*endclosest() { |
| 133 |
|
|
printf("filled %d buckets, averaging %d colors per list, %d of which were tested\n", |
| 134 |
|
|
nfill,(next-space-nfill)/nfill,tests/calls); |
| 135 |
|
|
}*/ |
