[FFmpeg-devel] [PATCH 2/5] libavcodec/jpeg2000dec.c: Modify image dimensions

[Michael Niedermayer]

On Mon, Jun 22, 2020 at 11:33:38PM +0200, Carl Eugen Hoyos wrote:
> Am Mo., 22. Juni 2020 um 23:32 Uhr schrieb Michael Niedermayer
> <michael at niedermayer.cc>:
> >
> > On Mon, Jun 22, 2020 at 12:12:05AM +0530, gautamramk at gmail.com wrote:
> > > From: Gautam Ramakrishnan <gautamramk at gmail.com>
> > >
> > > Reduce image size of the image if all components have
> > > a non zero sample separation. This is to replicate the
> > > output of opj_decompress.
> > > ---
> > >  libavcodec/jpeg2000dec.c | 19 ++++++++++++++-----
> > >  1 file changed, 14 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/libavcodec/jpeg2000dec.c b/libavcodec/jpeg2000dec.c
> > > index ab36009a2d..05e85f4317 100644
> > > --- a/libavcodec/jpeg2000dec.c
> > > +++ b/libavcodec/jpeg2000dec.c
> > > @@ -269,6 +269,8 @@ static int get_siz(Jpeg2000DecoderContext *s)
> > >      const enum AVPixelFormat *possible_fmts = NULL;
> > >      int possible_fmts_nb = 0;
> > >      int ret;
> > > +    int o_dimx, o_dimy; //original image dimensions.
> > > +    int dimx, dimy;
> > >
> > >      if (bytestream2_get_bytes_left(&s->g) < 36) {
> > >          av_log(s->avctx, AV_LOG_ERROR, "Insufficient space for SIZ\n");
> > > @@ -371,11 +373,18 @@ static int get_siz(Jpeg2000DecoderContext *s)
> > >      }
> > >
> > >      /* compute image size with reduction factor */
> > > -    ret = ff_set_dimensions(s->avctx,
> > > -            ff_jpeg2000_ceildivpow2(s->width  - s->image_offset_x,
> > > -                                               s->reduction_factor),
> > > -            ff_jpeg2000_ceildivpow2(s->height - s->image_offset_y,
> > > -                                               s->reduction_factor));
> > > +    o_dimx = ff_jpeg2000_ceildivpow2(s->width  - s->image_offset_x,
> > > +                                               s->reduction_factor);
> > > +    o_dimy = ff_jpeg2000_ceildivpow2(s->height - s->image_offset_y,
> > > +                                               s->reduction_factor);
> > > +    dimx = ff_jpeg2000_ceildiv(o_dimx, s->cdx[0]);
> > > +    dimy = ff_jpeg2000_ceildiv(o_dimy, s->cdy[0]);
> > > +    for (i = 1; i < s->ncomponents; i++) {
> > > +        dimx = FFMAX(dimx, ff_jpeg2000_ceildiv(o_dimx, s->cdx[i]));
> > > +        dimy = FFMAX(dimy, ff_jpeg2000_ceildiv(o_dimy, s->cdy[i]));
> > > +    }
> > > +
> > > +    ret = ff_set_dimensions(s->avctx, dimx, dimy);
> > >      if (ret < 0)
> > >          return ret;
> >
> > I think the resolution, the pixel format and any odd-format-handling
> > code probably need to be adjusted together.
> > Changing just the dimension code to select a higher resolution when
> > chroma or alpha planes are of higher resolution then luma. Will
> > probably not work if there is neither a pixel format selected that
> > represents that nor code to compensate for this (as mjpeg does)
> > but i might be missing something
> >
> > is there some testcase this fixes or improves ?
> 
> At least p1_01.j2k which has one component.

Ok, will apply
ive also tested the patchset over night with afl

Thanks


[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Good people do not need laws to tell them to act responsibly, while bad
people will find a way around the laws. -- Plato
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