On Thu, Jan 12, 2012 at 05:16:03PM +0200, Alon Levy wrote:
> On Tue, Jan 03, 2012 at 03:32:57PM +0200, Avi Kivity wrote:
> > ppm_save() spends upwards of 50% of its time doing divisions. Replace them
> > with shifts.
> >
>
> Reviewed-by: Alon Levy <al...@redhat.com>
>
> rmax/bmax/gmax are all uint8_t atm, could add a compilation error if
> sizeof(bmax)!=1 ever.
meant {r,g,b}bits.
>
> > Signed-off-by: Avi Kivity <a...@redhat.com>
> > ---
> > hw/vga.c | 10 ++++------
> > 1 files changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/hw/vga.c b/hw/vga.c
> > index ca79aa1..a228cde 100644
> > --- a/hw/vga.c
> > +++ b/hw/vga.c
> > @@ -2370,12 +2370,10 @@ int ppm_save(const char *filename, struct
> > DisplaySurface *ds)
> > v = *(uint32_t *)d;
> > else
> > v = (uint32_t) (*(uint16_t *)d);
> > - r = ((v >> ds->pf.rshift) & ds->pf.rmax) * 256 /
> > - (ds->pf.rmax + 1);
> > - g = ((v >> ds->pf.gshift) & ds->pf.gmax) * 256 /
> > - (ds->pf.gmax + 1);
> > - b = ((v >> ds->pf.bshift) & ds->pf.bmax) * 256 /
> > - (ds->pf.bmax + 1);
> > + /* Limited to 8 or fewer bits per channel: */
> > + r = ((v >> ds->pf.rshift) & ds->pf.rmax) << (8 - ds->pf.rbits);
> > + g = ((v >> ds->pf.gshift) & ds->pf.gmax) << (8 - ds->pf.gbits);
> > + b = ((v >> ds->pf.bshift) & ds->pf.bmax) << (8 - ds->pf.bbits);
> > *pbuf++ = r;
> > *pbuf++ = g;
> > *pbuf++ = b;
> > --
> > 1.7.7.1
> >
> >
>
