Quoth [email protected]:
> Quoth [email protected]:
> > Quoth [email protected]:
> > > Quoth [email protected]:
> > > > Hello 9fans,
> > > > For me, jpg(1) can't display most jpeg images I have. So I made a go
> > > > program that convert a jpeg image from stdin to a png image to stdout.
> > > > Assume that Plan 9's png is not broken ;)
> > > >
> > > > To test, go to https://thuychi.vn/anh.html
> > > > Of 50 images, Plan 9's jpg could only decode 3. The go library can
> > > > decode all of them.
> > > >
> > > > I hope that there will be go image/plan9 and a draw library that works
> > > > on Plan 9 too... Replace the jpg(1) programs with the Go version!
> > > >
> > > > bind /bin/jpgtopng.rc /bin/jpg, I think at least abaco don't need to
> > > > be modified.
> > > >
> > >
> > > Great, I think you just reminded me of an old bug in jpg that I'd
> > > been looking into (and then got distracted from). It looks like when
> > > we decode jpg images, we mishandle progresive jpgs that have scans
> > > that don't use interleaving, and have subsampled components. These
> > > aren't too common, but you'll run across them in the wild.
> > >
> > > Normally, we'll end up with the luminance channel coming through,
> > > but the chroma channels completely broken.
> > > Now that I'm looking at it again, I think this has something to do
> > > with how we walk the scans; data either comes in MCU or scan order,
> > > and we may be mangling this.
> > >
> > > this may not be so hard to fix.
> > >
> >
> > Alright, I think I found/fixed up the patch; there were two
> > issues that we had; first, when decoding the DC components, for
> > scans where Ns=1, we need to handle them in raster order, not
> > MCU order[1]. The change to progressivedc() handles the Nf==1
> > case to deal with the different scan order.
> >
> > The second case was that we don't need to have all frame
> > components present in the scan, and we needed to use Csj (the
> > component selector to pick the appropriate mage components from
> > the scan header.
> >
> > [1] https://www.w3.org/Graphics/JPEG/itu-t81.pdf, A.2.2
> > [2] https://www.w3.org/Graphics/JPEG/itu-t81.pdf, B.2.3
> >
>
> Whoops, had an out of bounds write, and now that I'm paging it
> in, I think I want to refactor the change and detangle a bit.
Ok -- this should be both working, and much easier to understand.
Instead of tangling both Nf=1 and Nf!=1 cases, it splits them;
the two cases naturally stand alone.
diff 07c4ebae5b344643d4a00b4532d216ef7291e42a uncommitted
--- a/sys/src/cmd/jpg/readjpg.c
+++ b/sys/src/cmd/jpg/readjpg.c
@@ -457,7 +457,7 @@
return 0;
}
if(Bread(h->fd, tmp, 2) != 2)
- Readerr:
+Readerr:
jpgerror(h, readerr);
n = int2(tmp, 0);
if(n < 2)
@@ -574,7 +574,7 @@
t->shift[v] = 8-cnt;
t->value[v] = t->val[t->valptr[i]+(code-t->mincode[i])];
- continueBytes:
+continueBytes:
v++;
}
@@ -899,16 +899,15 @@
void
progressivedc(Header *h, int comp, int Ah, int Al)
{
- int Ns, z, ri, mcu, nmcu;
+ int Ns, z, ri, mcu, nmcu;
int block, t, diff, qt, *dc, bn;
+ int x, y, H, V, nhor, nver, q;
Huffman *dcht;
uchar *ss;
- int i, Td[3], DC[3], blockno[3];
+ int i, j, Td[4], DC[4], scancomp[4], blockno[4];
ss= h->ss;
Ns = ss[0];
- if(Ns!=1 && Ns!=h->Nf)
- jpgerror(h, "ReadJPG: can't handle progressive with Ns!=1 and
Nf!=Ns in DC scan");
/* initialize data structures */
h->cnt = 0;
@@ -916,47 +915,81 @@
h->peek = -1;
for(i=0; i<Ns; i++){
- /*
- * JPEG requires scan components to be in same order as in
frame,
- * so if both have 3 we know scan is Y Cb Cr and there's no
need to
- * reorder
- */
nibbles(ss[2+2*i], &Td[i], &z); /* z is ignored */
DC[i] = 0;
+ for(j=0; j<h->Nf; j++)
+ if(h->comp[j].C == ss[1+2*i]){
+ scancomp[i] = j;
+ break;
+ }
+ if(j == h->Nf)
+ jpgerror(h, "ReadJPG: bad component selector in scan");
}
ri = h->ri;
- nmcu = h->nacross*h->ndown;
- memset(blockno, 0, sizeof blockno);
- for(mcu=0; mcu<nmcu; ){
- for(i=0; i<Ns; i++){
- if(Ns != 1) comp = i;
-
- dcht = &h->dcht[Td[i]];
- qt = h->qt[h->comp[comp].Tq][0];
- dc = h->dccoeff[comp];
- bn = blockno[i];
-
- for(block=0; block<h->nblock[comp]; block++){
+ if(Ns == 1){
+ /* ITU-T.81 A.2.2: scan in raster order if Ns = 1*/
+ comp = scancomp[0];
+ H = h->comp[comp].H;
+ V = h->comp[comp].V;
+ q = 8*h->Hmax/H;
+ nhor = (h->X+q-1)/q;
+ q = 8*h->Vmax/V;
+ nver = (h->Y+q-1)/q;
+ dcht = &h->dcht[Td[0]];
+ qt = h->qt[h->comp[comp].Tq][0];
+ dc = h->dccoeff[comp];
+ mcu = 0;
+ for(y=0; y<nver; y++){
+ for(x=0; x<nhor; x++){
+ bn = (x/H + h->nacross*(y/V))*H*V + H*(y%V) +
x%H;
if(Ah == 0){
t = decode(h, dcht);
diff = receive(h, t);
- DC[i] += diff;
- dc[bn] = qt*DC[i]<<Al;
+ DC[0] += diff;
+ dc[bn] = qt*DC[0]<<Al;
}else
dc[bn] |= qt*receivebit(h)<<Al;
- bn++;
+ /* process restart marker, if present */
+ mcu++;
+ if(ri>0 && mcu%ri==0){
+ restart(h, mcu);
+ DC[0] = 0;
+ }
}
- blockno[i] = bn;
}
-
- /* process restart marker, if present */
- mcu++;
- if(ri>0 && mcu<nmcu && mcu%ri==0){
- restart(h, mcu);
- for(i=0; i<Ns; i++)
- DC[i] = 0;
+ }else{
+ /* ITU-T.81 A.2.3: scan in MCU order otherwise */
+ nmcu = h->nacross*h->ndown;
+ memset(blockno, 0, sizeof blockno);
+ for(mcu=0; mcu<nmcu; ){
+ for(i=0; i<Ns; i++){
+ comp = scancomp[i];
+ dcht = &h->dcht[Td[i]];
+ qt = h->qt[h->comp[comp].Tq][0];
+ dc = h->dccoeff[comp];
+ bn = blockno[i];
+ for(block=0; block<h->nblock[comp]; block++){
+ if(Ah == 0){
+ t = decode(h, dcht);
+ diff = receive(h, t);
+ DC[i] += diff;
+ dc[bn] = qt*DC[i]<<Al;
+ }else
+ dc[bn] |= qt*receivebit(h)<<Al;
+ bn++;
+ }
+ blockno[i] = bn;
+ }
+
+ /* process restart marker, if present */
+ mcu++;
+ if(ri>0 && mcu<nmcu && mcu%ri==0){
+ restart(h, mcu);
+ for(i=0; i<Ns; i++)
+ DC[i] = 0;
+ }
}
}
}
@@ -1003,7 +1036,7 @@
mcu = 0;
for(y=0; y<nver; y++){
for(x=0; x<nhor; x++){
- /* Figure G-3 */
+ /* Figure G-3 */
if(eobrun > 0){
--eobrun;
continue;
@@ -1104,7 +1137,7 @@
for(x=0; x<nhor; x++){
/* Figure G-7 */
- /* arrange blockno to be in same sequence as original
scan calculation. */
+ /* arrange blockno to be in same sequence as original
scan calculation. */
tmcu = x/H + (nacross/H)*(y/V);
blockno = tmcu*H*V + H*(y%V) + x%H;
acc = ac[blockno];
@@ -1237,7 +1270,9 @@
static
void
-colormapall1(Header *h, int colorspace, Rawimage *image, int data0[8*8], int
data1[8*8], int data2[8*8], int mcu, int nacross)
+colormapall1(Header *h, int colorspace, Rawimage *image,
+ int data0[8*8], int data1[8*8], int data2[8*8],
+ int mcu, int nacross)
{
uchar *rpic, *gpic, *bpic, *rp, *gp, *bp;
int *p0, *p1, *p2;
@@ -1290,7 +1325,10 @@
static
void
-colormap(Header *h, int colorspace, Rawimage *image, int *data0[8*8], int
*data1[8*8], int *data2[8*8], int mcu, int nacross, int Hmax, int Vmax, int
*H, int *V)
+colormap(Header *h, int colorspace, Rawimage *image,
+ int *data0[8*8], int *data1[8*8], int *data2[8*8],
+ int mcu, int nacross, int Hmax, int Vmax,
+ int *H, int *V)
{
uchar *rpic, *gpic, *bpic;
int x, y, dx, dy, minx, miny;
------------------------------------------
9fans: 9fans
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