# [Pixman] [PATCH 13/14] pixman-filter: Nested polynomial for cubic

Bill Spitzak spitzak at gmail.com
Wed Apr 13 00:35:50 UTC 2016

```Because the integral function is relying on the range being clamped to the
non-zero portion for impulse filters and for box, and range checks are
missing for some of the other filter functions, I would be tempted to
remove the range check from here, and also from the impulse function (it
would return 1 for all x). Oded did not like that idea but I wonder if you
have any opinion.

On Mon, Apr 11, 2016 at 7:36 PM, SÃ¸ren Sandmann Pedersen <
soren.sandmann at gmail.com> wrote:

> From: Bill Spitzak <spitzak at gmail.com>
>
> v11: Restored range checks
>
> Signed-off-by: Bill Spitzak <spitzak at gmail.com>
> Reviewed-by: Oded Gabbay <oded.gabbay at gmail.com>
> ---
>  pixman/pixman-filter.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/pixman/pixman-filter.c b/pixman/pixman-filter.c
> index 4abd05f..db4ab6e 100644
> --- a/pixman/pixman-filter.c
> +++ b/pixman/pixman-filter.c
> @@ -109,14 +109,16 @@ general_cubic (double x, double B, double C)
>
>      if (ax < 1)
>      {
> -       return ((12 - 9 * B - 6 * C) * ax * ax * ax +
> -               (-18 + 12 * B + 6 * C) * ax * ax + (6 - 2 * B)) / 6;
> +       return (((12 - 9 * B - 6 * C) * ax +
> +                (-18 + 12 * B + 6 * C)) * ax * ax +
> +               (6 - 2 * B)) / 6;
>      }
> -    else if (ax >= 1 && ax < 2)
> +    else if (ax < 2)
>      {
> -       return ((-B - 6 * C) * ax * ax * ax +
> -               (6 * B + 30 * C) * ax * ax + (-12 * B - 48 * C) *
> -               ax + (8 * B + 24 * C)) / 6;
> +       return ((((-B - 6 * C) * ax +
> +                 (6 * B + 30 * C)) * ax +
> +                (-12 * B - 48 * C)) * ax +
> +               (8 * B + 24 * C)) / 6;
>      }
>      else
>      {
> --
> 1.7.11.7
>
>
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