[Pixman] [PATCH v14 08/22] pixman-filter: rename "scale" to "size" when it is 1/scale

[Søren Sandmann]

I suppose it's a little illogical that scale_x and scale_y really are the
reciprocal values of how much the source image should be scaled. I don't
remember exactly what I was thinking, but it might have something like
"this allows you to just pass t[0][0] and t[1][1] if you have a pure
scaling, which avoids a division". There is also kind of precedence in the
Pixman API since the transformation given as in the dst->source direction.

I don't really like "size" either though. It's not really the size of the
filter that we are specifying; it just happens to be proportional to it.

If it comes down to "size" and "scale", I prefer "scale".


Søren


On Sun, Mar 6, 2016 at 8:06 PM, <spitzak at gmail.com> wrote:

> From: Bill Spitzak <spitzak at gmail.com>
>
> This is to remove some confusion when reading the code. "scale" gets larger
> as the picture gets larger, while "size" (ie the size of the filter) gets
> smaller.
>
> v14: Removed changes to integral function
>
> Signed-off-by: Bill Spitzak <spitzak at gmail.com>
> Reviewed-by: Oded Gabbay <oded.gabbay at gmail.com>
> ---
>  pixman/pixman-filter.c | 18 +++++++++---------
>  pixman/pixman.h        |  6 +++---
>  2 files changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/pixman/pixman-filter.c b/pixman/pixman-filter.c
> index a29116a..c03a7f6 100644
> --- a/pixman/pixman-filter.c
> +++ b/pixman/pixman-filter.c
> @@ -221,7 +221,7 @@ static void
>  create_1d_filter (int              width,
>                   pixman_kernel_t  reconstruct,
>                   pixman_kernel_t  sample,
> -                 double           scale,
> +                 double           size,
>                   int              n_phases,
>                   pixman_fixed_t *p)
>  {
> @@ -251,8 +251,8 @@ create_1d_filter (int              width,
>             double pos = x + 0.5 - frac;
>             double rlow = - filters[reconstruct].width / 2.0;
>             double rhigh = rlow + filters[reconstruct].width;
> -           double slow = pos - scale * filters[sample].width / 2.0;
> -           double shigh = slow + scale * filters[sample].width;
> +           double slow = pos - size * filters[sample].width / 2.0;
> +           double shigh = slow + size * filters[sample].width;
>             double c = 0.0;
>             double ilow, ihigh;
>
> @@ -262,7 +262,7 @@ create_1d_filter (int              width,
>                 ihigh = MIN (shigh, rhigh);
>
>                 c = integral (reconstruct, ilow,
> -                             sample, 1.0 / scale, ilow - pos,
> +                             sample, 1.0 / size, ilow - pos,
>                               ihigh - ilow);
>             }
>
> @@ -335,12 +335,12 @@ filter_width (pixman_kernel_t reconstruct,
> pixman_kernel_t sample, double size)
>  }
>
>  /* Create the parameter list for a SEPARABLE_CONVOLUTION filter
> - * with the given kernels and scale parameters
> + * with the given kernels and size parameters
>   */
>  PIXMAN_EXPORT pixman_fixed_t *
>  pixman_filter_create_separable_convolution (int             *n_values,
> -                                           pixman_fixed_t   scale_x,
> -                                           pixman_fixed_t   scale_y,
> +                                           pixman_fixed_t   size_x,
> +                                           pixman_fixed_t   size_y,
>                                             pixman_kernel_t  reconstruct_x,
>                                             pixman_kernel_t  reconstruct_y,
>                                             pixman_kernel_t  sample_x,
> @@ -348,8 +348,8 @@ pixman_filter_create_separable_convolution (int
>      *n_values,
>                                             int
> subsample_bits_x,
>                                             int
> subsample_bits_y)
>  {
> -    double sx = fabs (pixman_fixed_to_double (scale_x));
> -    double sy = fabs (pixman_fixed_to_double (scale_y));
> +    double sx = fabs (pixman_fixed_to_double (size_x));
> +    double sy = fabs (pixman_fixed_to_double (size_y));
>      pixman_fixed_t *params;
>      int subsample_x, subsample_y;
>      int width, height;
> diff --git a/pixman/pixman.h b/pixman/pixman.h
> index 509ba5e..b012a33 100644
> --- a/pixman/pixman.h
> +++ b/pixman/pixman.h
> @@ -845,12 +845,12 @@ typedef enum
>  } pixman_kernel_t;
>
>  /* Create the parameter list for a SEPARABLE_CONVOLUTION filter
> - * with the given kernels and scale parameters.
> + * with the given kernels and size parameters.
>   */
>  pixman_fixed_t *
>  pixman_filter_create_separable_convolution (int             *n_values,
> -                                           pixman_fixed_t   scale_x,
> -                                           pixman_fixed_t   scale_y,
> +                                           pixman_fixed_t   size_x,
> +                                           pixman_fixed_t   size_y,
>                                             pixman_kernel_t  reconstruct_x,
>                                             pixman_kernel_t  reconstruct_y,
>                                             pixman_kernel_t  sample_x,
> --
> 1.9.1
>
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