ref: 53d55013598d7cd214d01cbf0b026844fe7ca8d2
dir: /sys/src/cmd/jpg/readgif.c/
#include <u.h>
#include <libc.h>
#include <bio.h>
#include <draw.h>
#include "imagefile.h"
typedef struct Entry Entry;
typedef struct Header Header;
struct Entry{
int prefix;
int exten;
};
struct Header{
Biobuf *fd;
char err[256];
jmp_buf errlab;
uchar buf[3*256];
char vers[8];
uchar *globalcmap;
int screenw;
int screenh;
int fields;
int bgrnd;
int aspect;
int flags;
int delay;
int trindex;
int loopcount;
Entry tbl[4096];
Rawimage **array;
Rawimage *new;
uchar *pic;
};
static char readerr[] = "ReadGIF: read error: %r";
static char extreaderr[] = "ReadGIF: can't read extension: %r";
static char memerr[] = "ReadGIF: malloc failed: %r";
static Rawimage** readarray(Header*, int);
static Rawimage* readone(Header*);
static void readheader(Header*);
static void skipextension(Header*);
static uchar* readcmap(Header*, int);
static uchar* decode(Header*, Rawimage*, Entry*);
static void interlace(Header*, Rawimage*);
static
void
clear(void **p)
{
if(*p){
free(*p);
*p = nil;
}
}
static
void
giffreeall(Header *h, int freeimage)
{
int i;
if(h->fd){
Bterm(h->fd);
h->fd = nil;
}
clear(&h->pic);
if(h->new){
clear(&h->new->cmap);
clear(&h->new->chans[0]);
clear(&h->new);
}
clear(&h->globalcmap);
if(freeimage && h->array!=nil){
for(i=0; h->array[i]; i++){
clear(&h->array[i]->cmap);
clear(&h->array[i]->chans[0]);
}
clear(&h->array);
}
}
static
void
giferror(Header *h, char *fmt, ...)
{
va_list arg;
va_start(arg, fmt);
vseprint(h->err, h->err+sizeof h->err, fmt, arg);
va_end(arg);
werrstr("%s", h->err);
giffreeall(h, 1);
longjmp(h->errlab, 1);
}
Rawimage**
readgif(int fd, int colorspace, int justone)
{
Rawimage **a;
Biobuf b;
Header *h;
char buf[ERRMAX];
buf[0] = '\0';
USED(colorspace);
if(Binit(&b, fd, OREAD) < 0)
return nil;
h = malloc(sizeof(Header));
if(h == nil){
Bterm(&b);
return nil;
}
memset(h, 0, sizeof(Header));
h->fd = &b;
errstr(buf, sizeof buf); /* throw it away */
if(setjmp(h->errlab))
a = nil;
else
a = readarray(h, justone);
giffreeall(h, 0);
free(h);
return a;
}
static
void
inittbl(Header *h)
{
int i;
Entry *tbl;
tbl = h->tbl;
for(i=0; i<258; i++) {
tbl[i].prefix = -1;
tbl[i].exten = i;
}
}
static
Rawimage**
readarray(Header *h, int justone)
{
Entry *tbl;
Rawimage *new, **array;
int c, nimages;
tbl = h->tbl;
readheader(h);
if(h->fields & 0x80)
h->globalcmap = readcmap(h, (h->fields&7)+1);
array = malloc(sizeof(Rawimage*));
if(array == nil)
giferror(h, memerr);
nimages = 0;
array[0] = nil;
h->array = array;
for(;;){
switch(c = Bgetc(h->fd)){
case Beof:
goto Return;
case 0x21: /* Extension (ignored) */
skipextension(h);
break;
case 0x2C: /* Image Descriptor */
inittbl(h);
new = readone(h);
if(new->fields & 0x80){
new->cmaplen = 3*(1<<((new->fields&7)+1));
new->cmap = readcmap(h, (new->fields&7)+1);
}else{
if(h->globalcmap == nil)
giferror(h, "ReadGIF: globalcmap missing");
new->cmaplen = 3*(1<<((h->fields&7)+1));
new->cmap = malloc(new->cmaplen);
if(new->cmap == nil)
giferror(h, memerr);
memmove(new->cmap, h->globalcmap, new->cmaplen);
}
h->new = new;
new->chans[0] = decode(h, new, tbl);
if(new->fields & 0x40)
interlace(h, new);
new->gifflags = h->flags;
new->gifdelay = h->delay;
new->giftrindex = h->trindex;
new->gifloopcount = h->loopcount;
array = realloc(h->array, (nimages+2)*sizeof(Rawimage*));
if(array == nil)
giferror(h, memerr);
array[nimages++] = new;
array[nimages] = nil;
h->array = array;
h->new = nil;
if(justone)
goto Return;
break;
case 0x3B: /* Trailer */
goto Return;
default:
fprint(2, "ReadGIF: unknown block type: 0x%.2x\n", c);
goto Return;
}
}
Return:
if(array[0]==nil || array[0]->chans[0] == nil)
giferror(h, "ReadGIF: no picture in file");
return array;
}
static
void
readheader(Header *h)
{
if(Bread(h->fd, h->buf, 13) != 13)
giferror(h, "ReadGIF: can't read header: %r");
memmove(h->vers, h->buf, 6);
if(strcmp(h->vers, "GIF87a")!=0 && strcmp(h->vers, "GIF89a")!=0)
giferror(h, "ReadGIF: can't recognize format %s", h->vers);
h->screenw = h->buf[6]+(h->buf[7]<<8);
h->screenh = h->buf[8]+(h->buf[9]<<8);
h->fields = h->buf[10];
h->bgrnd = h->buf[11];
h->aspect = h->buf[12];
h->flags = 0;
h->delay = 0;
h->trindex = 0;
h->loopcount = -1;
}
static
uchar*
readcmap(Header *h, int size)
{
uchar *map;
if(size > 8)
giferror(h, "ReadGIF: can't handles %d bits per pixel", size);
size = 3*(1<<size);
if(Bread(h->fd, h->buf, size) != size)
giferror(h, "ReadGIF: short read on color map");
map = malloc(size);
if(map == nil)
giferror(h, memerr);
memmove(map, h->buf, size);
return map;
}
static
Rawimage*
readone(Header *h)
{
Rawimage *i;
int left, top, width, height;
if(Bread(h->fd, h->buf, 9) != 9)
giferror(h, "ReadGIF: can't read image descriptor: %r");
i = malloc(sizeof(Rawimage));
if(i == nil)
giferror(h, memerr);
left = h->buf[0]+(h->buf[1]<<8);
top = h->buf[2]+(h->buf[3]<<8);
width = h->buf[4]+(h->buf[5]<<8);
height = h->buf[6]+(h->buf[7]<<8);
i->fields = h->buf[8];
i->r.min.x = left;
i->r.min.y = top;
i->r.max.x = left+width;
i->r.max.y = top+height;
i->nchans = 1;
i->chandesc = CRGB1;
memset(i->chans, 0, sizeof(i->chans));
return i;
}
static
int
readdata(Header *h, uchar *data)
{
int nbytes, n;
nbytes = Bgetc(h->fd);
if(nbytes < 0)
giferror(h, "ReadGIF: can't read data: %r");
if(nbytes == 0)
return 0;
n = Bread(h->fd, data, nbytes);
if(n < 0)
giferror(h, "ReadGIF: can't read data: %r");
if(n != nbytes)
fprint(2, "ReadGIF: short data subblock\n");
return n;
}
static
void
graphiccontrol(Header *h)
{
if(Bread(h->fd, h->buf, 5+1) != 5+1)
giferror(h, readerr);
h->flags = h->buf[1];
h->delay = h->buf[2]+(h->buf[3]<<8);
h->trindex = h->buf[4];
}
static
void
skipextension(Header *h)
{
int type, hsize, hasdata, n;
uchar data[256];
hsize = 0;
hasdata = 0;
type = Bgetc(h->fd);
switch(type){
case Beof:
giferror(h, extreaderr);
break;
case 0x01: /* Plain Text Extension */
hsize = 13;
hasdata = 1;
break;
case 0xF9: /* Graphic Control Extension */
graphiccontrol(h);
return;
case 0xFE: /* Comment Extension */
hasdata = 1;
break;
case 0xFF: /* Application Extension */
hsize = Bgetc(h->fd);
/* standard says this must be 11, but Adobe likes to put out 10-byte ones,
* so we pay attention to the field. */
hasdata = 1;
break;
default:
giferror(h, "ReadGIF: unknown extension");
}
if(hsize>0 && Bread(h->fd, h->buf, hsize) != hsize)
giferror(h, extreaderr);
if(!hasdata){
/*
* This code used to check h->buf[hsize-1] != 0
* and giferror if so, but if !hasdata, hsize == 0.
*/
return;
}
/* loop counter: Application Extension with NETSCAPE2.0 as string and 1 <loop.count> in data */
if(type == 0xFF && hsize==11 && memcmp(h->buf, "NETSCAPE2.0", 11)==0){
n = readdata(h, data);
if(n == 0)
return;
if(n==3 && data[0]==1)
h->loopcount = data[1] | (data[2]<<8);
}
while(readdata(h, data) != 0)
;
}
static
uchar*
decode(Header *h, Rawimage *i, Entry *tbl)
{
int c, incode, codesize, CTM, EOD, pici, datai, stacki, nbits, sreg, fc, code, piclen;
int csize, nentry, maxentry, first, ocode, ndata, nb;
uchar clip, *p, *pic;
uchar stack[4096], data[256];
if(Bread(h->fd, h->buf, 1) != 1)
giferror(h, "ReadGIF: can't read data: %r");
codesize = h->buf[0];
if(codesize>8 || 0>codesize)
giferror(h, "ReadGIF: can't handle codesize %d", codesize);
CTM =1<<codesize;
EOD = CTM+1;
piclen = (i->r.max.x-i->r.min.x)*(i->r.max.y-i->r.min.y);
i->chanlen = piclen;
pic = malloc(piclen);
if(pic == nil)
giferror(h, memerr);
h->pic = pic;
pici = 0;
ndata = 0;
datai = 0;
nbits = 0;
sreg = 0;
fc = 0;
Loop:
for(;;){
csize = codesize+1;
nentry = EOD+1;
maxentry = (1<<csize)-1;
first = 1;
ocode = -1;
for(;; ocode = incode) {
while(nbits < csize) {
if(datai == ndata){
ndata = readdata(h, data);
if(ndata == 0)
goto Return;
datai = 0;
}
c = data[datai++];
sreg |= c<<nbits;
nbits += 8;
}
code = sreg & ((1<<csize) - 1);
sreg >>= csize;
nbits -= csize;
if(code == EOD){
ndata = readdata(h, data);
if(ndata != 0)
fprint(2, "ReadGIF: unexpected data past EOD\n");
goto Return;
}
if(code == CTM)
goto Loop;
stacki = (sizeof stack)-1;
incode = code;
/* special case for KwKwK */
if(code == nentry) {
stack[stacki--] = fc;
code = ocode;
}
if(code > nentry){
fprint(2, "ReadGIF: GIF invalid, code out of range, %x > %x\n", code, nentry);
code = nentry;
}
for(c=code; stacki>0 && c>=0; c=tbl[c].prefix)
stack[stacki--] = tbl[c].exten;
nb = (sizeof stack)-(stacki+1);
if(pici+nb > piclen){
/* this common error is harmless
* we have to keep reading to keep the blocks in sync */
;
}else{
memmove(pic+pici, stack+stacki+1, sizeof stack - (stacki+1));
pici += nb;
}
fc = stack[stacki+1];
if(first){
first = 0;
continue;
}
#define early 0 /* peculiar tiff feature here for reference */
if(nentry == maxentry-early) {
if(csize >= 12)
continue;
csize++;
maxentry = (1<<csize);
if(csize < 12)
maxentry--;
}
tbl[nentry].prefix = ocode;
tbl[nentry].exten = fc;
nentry++;
}
}
Return:
if(i->cmap!=nil && i->cmaplen!=3*256){
clip = (i->cmaplen/3)-1;
for(p = pic; p < pic+piclen; p++)
if(*p > clip)
*p = clip;
}
h->pic = nil;
return pic;
}
static
void
interlace(Header *h, Rawimage *image)
{
uchar *pic;
Rectangle r;
int dx, yy, y;
uchar *ipic;
pic = image->chans[0];
r = image->r;
dx = r.max.x-r.min.x;
ipic = malloc(dx*(r.max.y-r.min.y));
if(ipic == nil)
giferror(h, nil);
/* Group 1: every 8th row, starting with row 0 */
yy = 0;
for(y=r.min.y; y<r.max.y; y+=8){
memmove(&ipic[(y-r.min.y)*dx], &pic[yy*dx], dx);
yy++;
}
/* Group 2: every 8th row, starting with row 4 */
for(y=r.min.y+4; y<r.max.y; y+=8){
memmove(&ipic[(y-r.min.y)*dx], &pic[yy*dx], dx);
yy++;
}
/* Group 3: every 4th row, starting with row 2 */
for(y=r.min.y+2; y<r.max.y; y+=4){
memmove(&ipic[(y-r.min.y)*dx], &pic[yy*dx], dx);
yy++;
}
/* Group 4: every 2nd row, starting with row 1 */
for(y=r.min.y+1; y<r.max.y; y+=2){
memmove(&ipic[(y-r.min.y)*dx], &pic[yy*dx], dx);
yy++;
}
free(image->chans[0]);
image->chans[0] = ipic;
}