ref: faa625a1d5ab47ac0438b2cea5b2bde1ea747b8b
dir: /sys/src/cmd/jpg/torgbv.c/
#include <u.h>
#include <libc.h>
#include <bio.h>
#include <draw.h>
#include "imagefile.h"
#include "rgbv.h"
#include "ycbcr.h"
#define CLAMPOFF 128
static int clamp[CLAMPOFF+256+CLAMPOFF];
static int inited;
void*
_remaperror(char *fmt, ...)
{
va_list arg;
char buf[ERRMAX];
va_start(arg, fmt);
vseprint(buf, buf+sizeof buf, fmt, arg);
va_end(arg);
errstr(buf, sizeof buf);
return nil;
}
Rawimage*
torgbv(Rawimage *i, int errdiff)
{
int j, k, rgb, x, y, er, eg, eb, col, t;
int r, g, b, r1, g1, b1;
int *ered, *egrn, *eblu, *rp, *gp, *bp;
int bpc;
uint *map3;
uchar *closest;
Rawimage *im;
int dx, dy;
char err[ERRMAX];
uchar *cmap, *cm, *in, *out, *inp, *outp, cmap1[3*256], map[256], *rpic, *bpic, *gpic;
err[0] = '\0';
errstr(err, sizeof err); /* throw it away */
im = malloc(sizeof(Rawimage));
if(im == nil)
return nil;
memset(im, 0, sizeof(Rawimage));
im->chans[0] = malloc(i->chanlen);
if(im->chans[0] == nil){
free(im);
return nil;
}
im->r = i->r;
im->nchans = 1;
im->chandesc = CRGBV;
im->chanlen = i->chanlen;
dx = i->r.max.x-i->r.min.x;
dy = i->r.max.y-i->r.min.y;
cmap = i->cmap;
if(inited == 0){
inited = 1;
for(j=0; j<CLAMPOFF; j++)
clamp[j] = 0;
for(j=0; j<256; j++)
clamp[CLAMPOFF+j] = (j>>4);
for(j=0; j<CLAMPOFF; j++)
clamp[CLAMPOFF+256+j] = (255>>4);
}
in = i->chans[0];
inp = in;
out = im->chans[0];
outp = out;
ered = malloc((dx+1)*sizeof(int));
egrn = malloc((dx+1)*sizeof(int));
eblu = malloc((dx+1)*sizeof(int));
if(ered==nil || egrn==nil || eblu==nil){
free(im->chans[0]);
free(im);
free(ered);
free(egrn);
free(eblu);
return _remaperror("remap: malloc failed: %r");
}
memset(ered, 0, (dx+1)*sizeof(int));
memset(egrn, 0, (dx+1)*sizeof(int));
memset(eblu, 0, (dx+1)*sizeof(int));
switch(i->chandesc){
default:
return _remaperror("remap: can't recognize channel type %d", i->chandesc);
case CRGB1:
if(cmap == nil)
return _remaperror("remap: image has no color map");
if(i->nchans != 1)
return _remaperror("remap: can't handle nchans %d", i->nchans);
for(j=1; j<=8; j++)
if(i->cmaplen == 3*(1<<j))
break;
if(j > 8)
return _remaperror("remap: can't do colormap size 3*%d", i->cmaplen/3);
if(i->cmaplen != 3*256){
/* to avoid a range check in inner loop below, make a full-size cmap */
memmove(cmap1, cmap, i->cmaplen);
cmap = cmap1;
}
if(errdiff == 0){
k = 0;
for(j=0; j<256; j++){
r = cmap[k]>>4;
g = cmap[k+1]>>4;
b = cmap[k+2]>>4;
k += 3;
map[j] = closestrgb[b+16*(g+16*r)];
}
for(j=0; j<i->chanlen; j++)
out[j] = map[in[j]];
}else{
/* modified floyd steinberg, coefficients (1 0) 3/16, (0, 1) 3/16, (1, 1) 7/16 */
for(y=0; y<dy; y++){
er = 0;
eg = 0;
eb = 0;
rp = ered;
gp = egrn;
bp = eblu;
for(x=0; x<dx; x++){
cm = &cmap[3 * *inp++];
r = cm[0] +*rp;
g = cm[1] +*gp;
b = cm[2] +*bp;
/* sanity checks are new */
if(r >= 256+CLAMPOFF)
r = 0;
if(g >= 256+CLAMPOFF)
g = 0;
if(b >= 256+CLAMPOFF)
b = 0;
r1 = clamp[r+CLAMPOFF];
g1 = clamp[g+CLAMPOFF];
b1 = clamp[b+CLAMPOFF];
if(r1 >= 16 || g1 >= 16 || b1 >= 16)
col = 0;
else
col = closestrgb[b1+16*(g1+16*r1)];
*outp++ = col;
rgb = rgbmap[col];
r -= (rgb>>16) & 0xFF;
t = (3*r)>>4;
*rp++ = t+er;
*rp += t;
er = r-3*t;
g -= (rgb>>8) & 0xFF;
t = (3*g)>>4;
*gp++ = t+eg;
*gp += t;
eg = g-3*t;
b -= rgb & 0xFF;
t = (3*b)>>4;
*bp++ = t+eb;
*bp += t;
eb = b-3*t;
}
}
}
break;
case CYCbCr:
bpc = 1;
rpic = i->chans[0];
gpic = i->chans[1];
bpic = i->chans[2];
closest = closestycbcr;
map3 = ycbcrmap;
if(i->nchans != 3)
return _remaperror("remap: RGB image has %d channels", i->nchans);
goto Threecolor;
case CRGB:
bpc = 1;
rpic = i->chans[0];
gpic = i->chans[1];
bpic = i->chans[2];
if(i->nchans != 3)
return _remaperror("remap: RGB image has %d channels", i->nchans);
goto rgbgen;
case CRGB24:
bpc = 3;
bpic = i->chans[0];
gpic = i->chans[0] + 1;
rpic = i->chans[0] + 2;
goto rgbgen;
case CRGBA32:
bpc = 4;
/* i->chans[0]+0 is alpha */
bpic = i->chans[0] + 1;
gpic = i->chans[0] + 2;
rpic = i->chans[0] + 3;
rgbgen:
closest = closestrgb;
map3 = rgbmap;
Threecolor:
if(errdiff == 0){
outp = out;
for(j=0; j<i->chanlen; j+=bpc){
r = rpic[j]>>4;
g = gpic[j]>>4;
b = bpic[j]>>4;
*outp++ = closest[b+16*(g+16*r)];
}
}else{
/* modified floyd steinberg, coefficients (1 0) 3/16, (0, 1) 3/16, (1, 1) 7/16 */
for(y=0; y<dy; y++){
er = 0;
eg = 0;
eb = 0;
rp = ered;
gp = egrn;
bp = eblu;
for(x=0; x<dx; x++){
r = *rpic + *rp;
g = *gpic + *gp;
b = *bpic + *bp;
rpic += bpc;
gpic += bpc;
bpic += bpc;
/*
* Errors can be uncorrectable if converting from YCbCr,
* since we can't guarantee that an extremal value of one of
* the components selects a color with an extremal value.
* If we don't, the errors accumulate without bound. This
* doesn't happen in RGB because the closest table can guarantee
* a color on the edge of the gamut, producing a zero error in
* that component. For the rotation YCbCr space, there may be
* no color that can guarantee zero error at the edge.
* Therefore we must clamp explicitly rather than by assuming
* an upper error bound of CLAMPOFF. The performance difference
* is miniscule anyway.
*/
if(r < 0)
r = 0;
else if(r > 255)
r = 255;
if(g < 0)
g = 0;
else if(g > 255)
g = 255;
if(b < 0)
b = 0;
else if(b > 255)
b = 255;
r1 = r>>4;
g1 = g>>4;
b1 = b>>4;
col = closest[b1+16*(g1+16*r1)];
*outp++ = col;
rgb = map3[col];
r -= (rgb>>16) & 0xFF;
t = (3*r)>>4;
*rp++ = t+er;
*rp += t;
er = r-3*t;
g -= (rgb>>8) & 0xFF;
t = (3*g)>>4;
*gp++ = t+eg;
*gp += t;
eg = g-3*t;
b -= rgb & 0xFF;
t = (3*b)>>4;
*bp++ = t+eb;
*bp += t;
eb = b-3*t;
}
}
}
break;
case CYA16:
bpc = 2;
/* i->chans[0] + 0 is alpha */
rpic = i->chans[0] + 1;
goto greygen;
case CY:
bpc = 1;
rpic = i->chans[0];
if(i->nchans != 1)
return _remaperror("remap: Y image has %d chans", i->nchans);
greygen:
if(errdiff == 0){
for(j=0; j<i->chanlen; j+=bpc){
r = rpic[j]>>4;
*outp++ = closestrgb[r+16*(r+16*r)];
}
}else{
/* modified floyd steinberg, coefficients (1 0) 3/16, (0, 1) 3/16, (1, 1) 7/16 */
for(y=0; y<dy; y++){
er = 0;
rp = ered;
for(x=0; x<dx; x++){
r = *rpic + *rp;
rpic += bpc;
r1 = clamp[r+CLAMPOFF];
col = closestrgb[r1+16*(r1+16*r1)];
*outp++ = col;
rgb = rgbmap[col];
r -= (rgb>>16) & 0xFF;
t = (3*r)>>4;
*rp++ = t+er;
*rp += t;
er = r-3*t;
}
}
}
break;
}
free(ered);
free(egrn);
free(eblu);
return im;
}