ref: 2c6cc121339ade33ac5aa4b46356df1cd5469fbe
dir: /sys/src/cmd/jpg/readpng.c/
#include <u.h>
#include <libc.h>
#include <ctype.h>
#include <bio.h>
#include <flate.h>
#include <draw.h>
#include "imagefile.h"
int debug;
enum
{
IDATSIZE = 8*1024*1024,
/* filtering algorithms */
FilterNone = 0, /* new[x][y] = buf[x][y] */
FilterSub = 1, /* new[x][y] = buf[x][y] + new[x-1][y] */
FilterUp = 2, /* new[x][y] = buf[x][y] + new[x][y-1] */
FilterAvg = 3, /* new[x][y] = buf[x][y] + (new[x-1][y]+new[x][y-1])/2 */
FilterPaeth = 4, /* new[x][y] = buf[x][y] + paeth(new[x-1][y],new[x][y-1],new[x-1][y-1]) */
FilterLast = 5,
PropertyBit = 1<<5,
};
typedef struct ZlibR ZlibR;
typedef struct ZlibW ZlibW;
struct ZlibW
{
uchar *data; /* Rawimage data */
int ndata;
int noutchan;
int chandesc;
int nchan;
uchar *scan; /* new scanline */
uchar *lastscan; /* previous scan line */
int scanlen; /* scan line length */
int scanpos; /* scan position */
int dx; /* width of image */
int dy; /* height of image */
int bpc; /* bits per channel (per pixel) */
int y; /* current scan line */
int pass; /* adam7 pass#; 0 means no adam7 */
uchar palette[3*256]; /* color palette */
int palsize; /* number of palette entries */
};
struct ZlibR
{
Biobuf *io; /* input buffer */
uchar *buf; /* malloc'ed staging buffer */
uchar *p; /* next byte to decompress */
uchar *e; /* end of buffer */
ZlibW *w;
};
static ulong *crctab;
static uchar PNGmagic[] = { 137, 'P', 'N', 'G', '\r', '\n', 26, '\n'};
static ulong
get4(uchar *a)
{
return (a[0]<<24) | (a[1]<<16) | (a[2]<<8) | a[3];
}
static
void
pnginit(void)
{
static int inited;
if(inited)
return;
inited = 1;
crctab = mkcrctab(0xedb88320);
if(crctab == nil)
sysfatal("mkcrctab error");
inflateinit();
}
static
void*
pngmalloc(ulong n, int clear)
{
void *p;
p = mallocz(n, clear);
if(p == nil)
sysfatal("malloc: %r");
return p;
}
static int
getchunk(Biobuf *b, char *type, uchar *d, int m)
{
uchar buf[8];
ulong crc = 0, crc2;
int n, nr;
if(Bread(b, buf, 8) != 8)
return -1;
n = get4(buf);
memmove(type, buf+4, 4);
type[4] = 0;
if(n > m)
sysfatal("getchunk needed %d, had %d", n, m);
nr = Bread(b, d, n);
if(nr != n)
sysfatal("getchunk read %d, expected %d", nr, n);
crc = blockcrc(crctab, crc, type, 4);
crc = blockcrc(crctab, crc, d, n);
if(Bread(b, buf, 4) != 4)
sysfatal("getchunk tlr failed");
crc2 = get4(buf);
if(crc != crc2)
sysfatal("getchunk crc failed");
return n;
}
static int
zread(void *va)
{
ZlibR *z = va;
char type[5];
int n;
if(z->p >= z->e){
Again:
z->p = z->buf;
z->e = z->p;
n = getchunk(z->io, type, z->p, IDATSIZE);
if(n < 0 || strcmp(type, "IEND") == 0)
return -1;
z->e = z->p + n;
if(!strcmp(type,"PLTE")){
if(n < 3 || n > 3*256 || n%3)
sysfatal("invalid PLTE chunk len %d", n);
memcpy(z->w->palette, z->p, n);
z->w->palsize = 256;
goto Again;
}
if(type[0] & PropertyBit)
goto Again; /* skip auxiliary chunks fornow */
if(strcmp(type,"IDAT")){
sysfatal("unrecognized mandatory chunk %s", type);
goto Again;
}
}
return *z->p++;
}
static uchar
paeth(uchar a, uchar b, uchar c)
{
int p, pa, pb, pc;
p = a + b - c;
pa = abs(p - a);
pb = abs(p - b);
pc = abs(p - c);
if(pa <= pb && pa <= pc)
return a;
else if(pb <= pc)
return b;
return c;
}
static void
unfilter(int alg, uchar *buf, uchar *up, int len, int bypp)
{
int i;
switch(alg){
default:
fprint(2, "unknown filtering scheme %d\n", alg);
case FilterNone:
break;
case FilterSub:
for(i = bypp; i < len; ++i)
buf[i] += buf[i-bypp];
break;
case FilterUp:
for(i = 0; i < len; ++i)
buf[i] += up[i];
break;
case FilterAvg:
for(i = 0; i < bypp; ++i)
buf[i] += (0+up[i])/2;
for(; i < len; ++i)
buf[i] += (buf[i-bypp]+up[i])/2;
break;
case FilterPaeth:
for(i = 0; i < bypp; ++i)
buf[i] += paeth(0, up[i], 0);
for(; i < len; ++i)
buf[i] += paeth(buf[i-bypp], up[i], up[i-bypp]);
break;
}
}
struct {
int x;
int y;
int dx;
int dy;
} adam7[] = {
{0,0,1,1}, /* eve alone */
{0,0,8,8}, /* pass 1 */
{4,0,8,8}, /* pass 2 */
{0,4,4,8}, /* pass 3 */
{2,0,4,4}, /* pass 4 */
{0,2,2,4}, /* pass 5 */
{1,0,2,2}, /* pass 6 */
{0,1,1,2}, /* pass 7 */
};
static void
scan(int len, ZlibW *z)
{
int chan, i, j, nbit, off, val;
uchar pixel[4], *p, *w;
unfilter(z->scan[0], z->scan+1, z->lastscan+1, len-1, (z->nchan*z->bpc+7)/8);
/*
* loop over raw bits extracting pixel values and converting to 8-bit
*/
nbit = 0;
chan = 0;
val = 0;
off = z->y*z->dx + adam7[z->pass].x;
w = z->data + z->noutchan*off;
p = z->scan+1; /* skip alg byte */
len--;
for(i=0; i<len*8; i++){
val <<= 1;
if(p[i>>3] & (1<<(7-(i&7))))
val++;
if(++nbit == z->bpc){
/* finished the value */
pixel[chan++] = (val*255)/((1<<z->bpc)-1);
val = 0;
nbit = 0;
if(chan == z->nchan){
/* finished the pixel */
if(off < z->dx*z->dy){
if(z->nchan < 3 && z->palsize){
j = pixel[0];
if(z->bpc < 8)
j >>= 8-z->bpc;
if(j >= z->palsize)
sysfatal("index %d >= palette size %d", j, z->palsize);
pixel[3] = pixel[1]; /* alpha */
pixel[0] = z->palette[3*j];
pixel[1] = z->palette[3*j+1];
pixel[2] = z->palette[3*j+2];
}
switch(z->chandesc){
case CYA16:
// print("%.2x%.2x ", pixel[0], pixel[1]);
*w++ = pixel[1];
*w++ += (pixel[0]*pixel[1])/255;
break;
case CRGBA32:
// print("%.2x%.2x%.2x%.2x ", pixel[0], pixel[1], pixel[2], pixel[3]);
*w++ += pixel[3];
*w++ += (pixel[2]*pixel[3])/255;
*w++ += (pixel[1]*pixel[3])/255;
*w++ += (pixel[0]*pixel[3])/255;
break;
case CRGB24:
*w++ = pixel[2];
*w++ = pixel[1];
case CY:
*w++ = pixel[0];
break;
}
w += (adam7[z->pass].dx-1)*z->noutchan;
}
off += adam7[z->pass].dx;
if(off >= (z->y+1)*z->dx){
/* finished the line */
return;
}
chan = 0;
}
}
}
sysfatal("scan line too short");
}
static int
scanbytes(ZlibW *z)
{
int bits, n, adx, dx;
if(adam7[z->pass].y >= z->dy || adam7[z->pass].x >= z->dx)
return 0;
adx = adam7[z->pass].dx;
dx = z->dx - adam7[z->pass].x;
if(dx <= 0)
n = 1;
else
n = (dx+adx-1)/adx;
if(n != 1 + (z->dx - (adam7[z->pass].x+1)) / adam7[z->pass].dx){
fprint(2, "%d/%d != 1+(%d-1)/%d = %d\n",
z->dx - adam7[z->pass].x - 1 + adx, adx,
z->dx - (adam7[z->pass].x+1), adam7[z->pass].dx,
1 + (z->dx - (adam7[z->pass].x+1)) / adam7[z->pass].dx);
}
bits = n*z->bpc*z->nchan;
return 1 + (bits+7)/8;
}
static int
nextpass(ZlibW *z)
{
int len;
memset(z->lastscan, 0, z->scanlen);
do{
z->pass = (z->pass+1)%8;
z->y = adam7[z->pass].y;
len = scanbytes(z);
}while(len < 2);
return len;
}
static int
zwrite(void *vz, void *vbuf, int n)
{
int oldn, m, len;
uchar *buf, *t;
ZlibW *z;
z = vz;
buf = vbuf;
oldn = n;
len = scanbytes(z);
if(len < 2)
len = nextpass(z);
while(n > 0){
m = len - z->scanpos;
if(m > n){
/* save final partial line */
memmove(z->scan+z->scanpos, buf, n);
z->scanpos += n;
break;
}
/* fill line */
memmove(z->scan+z->scanpos, buf, m);
buf += m;
n -= m;
/* process line */
scan(len, z);
t = z->scan;
z->scan = z->lastscan;
z->lastscan = t;
z->scanpos = 0;
z->y += adam7[z->pass].dy;
if(z->y >= z->dy)
len = nextpass(z);
}
return oldn;
}
static Rawimage*
readslave(Biobuf *b)
{
char type[5];
int bpc, colorfmt, dx, dy, err, n, nchan, nout, useadam7;
uchar *buf, *h;
Rawimage *image;
ZlibR zr;
ZlibW zw;
buf = pngmalloc(IDATSIZE, 0);
if(Bread(b, buf, sizeof PNGmagic) != sizeof PNGmagic
|| memcmp(PNGmagic, buf, sizeof PNGmagic) != 0)
sysfatal("bad PNGmagic");
n = getchunk(b, type, buf, IDATSIZE);
if(n < 13 || strcmp(type,"IHDR") != 0)
sysfatal("missing IHDR chunk");
h = buf;
dx = get4(h);
h += 4;
dy = get4(h);
h += 4;
if(dx <= 0 || dy <= 0)
sysfatal("impossible image size %dx%d", dx, dy);
if(debug)
fprint(2, "readpng %dx%d\n", dx, dy);
bpc = *h++;
colorfmt = *h++;
nchan = 0;
if(*h++ != 0)
sysfatal("only deflate supported for now [%d]", h[-1]);
if(*h++ != FilterNone)
sysfatal("only FilterNone supported for now [%d]", h[-1]);
useadam7 = *h++;
USED(h);
image = pngmalloc(sizeof(Rawimage), 1);
image->r = Rect(0, 0, dx, dy);
nout = 0;
switch(colorfmt){
case 0: /* grey */
if(bpc != 1 && bpc != 2 && bpc != 4 && bpc != 8 && bpc != 16)
sysfatal("invalid greyscale bpc %d", bpc);
image->nchans = 1;
image->chandesc = CY;
nout = 1;
nchan = 1;
break;
case 2: /* rgb */
if(bpc != 8 && bpc != 16)
sysfatal("invalid rgb bpc %d", bpc);
image->nchans = 1;
image->chandesc = CRGB24;
nout = 3;
nchan = 3;
break;
case 3: /* indexed rgb with PLTE */
if(bpc != 1 && bpc != 2 && bpc != 4 && bpc != 8)
sysfatal("invalid indexed rgb bpc %d", bpc);
image->nchans = 1;
image->chandesc = CRGB24;
nout = 3;
nchan = 1;
break;
case 4: /* grey+alpha */
if(bpc != 8 && bpc != 16)
sysfatal("invalid grey+alpha bpc %d", bpc);
image->nchans = 1;
image->chandesc = CYA16;
nout = 2;
nchan = 2;
break;
case 6: /* rgb+alpha */
if(bpc != 8 && bpc != 16)
sysfatal("invalid rgb+alpha bpc %d", bpc);
image->nchans = 1;
image->chandesc = CRGBA32;
nout = 4;
nchan = 4;
break;
default:
sysfatal("unsupported color scheme %d", h[-1]);
}
image->chanlen = dx*dy*nout;
image->chans[0] = pngmalloc(image->chanlen, 0);
memset(image->chans[0], 0, image->chanlen);
memset(&zr, 0, sizeof zr);
zr.w = &zw;
zr.io = b;
zr.buf = buf;
memset(&zw, 0, sizeof zw);
if(useadam7)
zw.pass = 1;
zw.data = image->chans[0];
zw.ndata = image->chanlen;
zw.chandesc = image->chandesc;
zw.noutchan = nout;
zw.dx = dx;
zw.dy = dy;
zw.scanlen = (nchan*dx*bpc+7)/8+1;
zw.scan = pngmalloc(zw.scanlen, 1);
zw.lastscan = pngmalloc(zw.scanlen, 1);
zw.nchan = nchan;
zw.bpc = bpc;
err = inflatezlib(&zw, zwrite, &zr, zread);
if(err)
sysfatal("inflatezlib %s\n", flateerr(err));
free(buf);
free(zw.scan);
free(zw.lastscan);
return image;
}
Rawimage**
Breadpng(Biobuf *b, int colorspace)
{
Rawimage **array, *r;
if(colorspace != CRGB){
werrstr("ReadPNG: unknown color space %d", colorspace);
return nil;
}
pnginit();
array = malloc(2*sizeof(*array));
if(array==nil)
return nil;
r = readslave(b);
array[0] = r;
array[1] = nil;
return array;
}
Rawimage**
readpng(int fd, int colorspace)
{
Biobuf b;
Rawimage **a;
if(Binit(&b, fd, OREAD) < 0)
return nil;
a = Breadpng(&b, colorspace);
Bterm(&b);
return a;
}