Am Mo., 22. Juni 2020 um 23:32 Uhr schrieb Michael Niedermayer
<mich...@niedermayer.cc>:
>
> On Mon, Jun 22, 2020 at 12:12:05AM +0530, gautamr...@gmail.com wrote:
> > From: Gautam Ramakrishnan <gautamr...@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.
Carl Eugen
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