Nicolas George (2019-01-02):
> Uwe Freese (2019-01-01):
> > > This can be optimized, and since it is the inner loop of the filter, I
> > > think it is worth it. You can declare a pointer that will stay the same
> > > for the whole y loop:
> > >
> > > double *xweight = uglarmtable + (y - logo_y1) * (logo_w - 1);
> > >
> > > and then use it in that loop:
> > >
> > > interpd += ... * xweight[abs(bx - (x - logo_x1))];
> > >
> > > It avoids a lot of multiplications.
>
> > Secondly, I don't exactly understand how *xweight in your example should be
> > used (and would mean smaller or easier code).
>
> XXX
Sorry, forgot to fill that part before sending.
Completely untested code:
double *table_t, *table_b, *table_l, *table_r;
table_t = uglarmtable + x + table_stride * y;
table_b = uglarmtable + x + table_stride * (logo_h - y - 1);
table_l = uglarmtable + table_stride * (y - 1) + x;
table_r = uglarmtable + table_stride * (y - 1) + logo_w - x - 1;
/* top+bottom on the left of the current point */
for (bx = 0; bx < x; bx++) {
weightsum += table_t;
weightsum += table_b;
table_t--;
table_b--;
}
/* top+bottom on the right of the current point */
for (; bx < logo_w; bx++) {
weightsum += table_t;
weightsum += table_b;
table_t++;
table_b++;
}
/* left+right above the current point */
for (by = 1; by < y; by++) {
weightsum += *table_l;
weightsum += *table_r;
table_l -= table_stride;
table_r -= table_stride;
}
/* left+right below the current point */
for (; by < logo_w - 1; by++) {
weightsum += *table_l;
weightsum += *table_r;
table_l += table_stride;
table_r += table_stride;
}
av_assert2(table_t == uglarmtable + (logo_w - x) + table_stride * y);
av_assert2(table_b == uglarmtable + (logo_w - x) + table_stride * (logo_h -
y - 1));
av_assert2(table_l == uglarmtable + table_stride * (logo_h - y - 1) + x);
av_assert2(table_r == uglarmtable + table_stride * (logo_h - y - 1) +
logo_w - x - 1;
That makes more lines, but the lines are way simpler: no tricky
arithmetic, all blocks almost identical, with the changes easy to see
and understand.
Regards,
--
Nicolas George
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