[FFmpeg-devel] [PATCH 1/2] avfilter/vf_geq: allow user to set interpolation method

[Michael Niedermayer]

On Fri, Oct 11, 2019 at 06:29:45PM +0200, Paul B Mahol wrote:
> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> ---
>  doc/filters.texi     |  8 ++++++++
>  libavfilter/vf_geq.c | 27 +++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 55a8ebae56..6f9ebf6085 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -11019,6 +11019,14 @@ red/green/blue component. Return 0 if there is no such component.
>  @item alpha(x, y)
>  Return the value of the pixel at location (@var{x}, at var{y}) of the alpha
>  plane. Return 0 if there is no such plane.
> +
> + at item interpolation
> +Set one of interpolation methods:
> + at table @option
> + at item nearest, n
> + at item bilinear, b
> + at end table
> +Default is bilinear.
>  @end table
>  
>  For functions, if @var{x} and @var{y} are outside the area, the value will be
> diff --git a/libavfilter/vf_geq.c b/libavfilter/vf_geq.c
> index 91eb9685f9..b7932f0b04 100644
> --- a/libavfilter/vf_geq.c
> +++ b/libavfilter/vf_geq.c
> @@ -33,6 +33,12 @@
>  #include "libavutil/pixdesc.h"
>  #include "internal.h"
>  
> +enum InterpolationMethods {
> +    INTERP_NEAREST,
> +    INTERP_BILINEAR,
> +    NB_INTERP
> +};
> +
>  static const char *const var_names[] = {   "X",   "Y",   "W",   "H",   "N",   "SW",   "SH",   "T",        NULL };
>  enum                                   { VAR_X, VAR_Y, VAR_W, VAR_H, VAR_N, VAR_SW, VAR_SH, VAR_T, VAR_VARS_NB };
>  
> @@ -46,6 +52,7 @@ typedef struct GEQContext {
>      double values[VAR_VARS_NB]; ///< expression values
>      int hsub, vsub;             ///< chroma subsampling
>      int planes;                 ///< number of planes
> +    int interpolation;
>      int is_rgb;
>      int bps;
>  } GEQContext;
> @@ -70,6 +77,12 @@ static const AVOption geq_options[] = {
>      { "g",          "set green expression",       OFFSET(expr_str[G]), AV_OPT_TYPE_STRING, {.str=NULL}, CHAR_MIN, CHAR_MAX, FLAGS },
>      { "blue_expr",  "set blue expression",        OFFSET(expr_str[B]), AV_OPT_TYPE_STRING, {.str=NULL}, CHAR_MIN, CHAR_MAX, FLAGS },
>      { "b",          "set blue expression",        OFFSET(expr_str[B]), AV_OPT_TYPE_STRING, {.str=NULL}, CHAR_MIN, CHAR_MAX, FLAGS },
> +    { "interpolation","set interpolation method", OFFSET(interpolation), AV_OPT_TYPE_INT, {.i64=INTERP_BILINEAR}, 0, NB_INTERP-1, FLAGS, "interp" },
> +    { "i",          "set interpolation method",   OFFSET(interpolation), AV_OPT_TYPE_INT, {.i64=INTERP_BILINEAR}, 0, NB_INTERP-1, FLAGS, "interp" },
> +    { "nearest",    "nearest interpolation",      0,                   AV_OPT_TYPE_CONST, {.i64=INTERP_NEAREST},  0, 0, FLAGS, "interp" },
> +    { "n",          "nearest interpolation",      0,                   AV_OPT_TYPE_CONST, {.i64=INTERP_NEAREST},  0, 0, FLAGS, "interp" },
> +    { "bilinear",   "bilinear interpolation",     0,                   AV_OPT_TYPE_CONST, {.i64=INTERP_BILINEAR}, 0, 0, FLAGS, "interp" },
> +    { "b",          "bilinear interpolation",     0,                   AV_OPT_TYPE_CONST, {.i64=INTERP_BILINEAR}, 0, 0, FLAGS, "interp" },
>      {NULL},
>  };
>  
> @@ -88,6 +101,7 @@ static inline double getpix(void *priv, double x, double y, int plane)
>      if (!src)
>          return 0;
>  
> +    if (geq->interpolation == INTERP_BILINEAR) {
>      xi = x = av_clipf(x, 0, w - 2);
>      yi = y = av_clipf(y, 0, h - 2);
>  

> @@ -104,6 +118,19 @@ static inline double getpix(void *priv, double x, double y, int plane)
>          return (1-y)*((1-x)*src[xi +  yi    * linesize] + x*src[xi + 1 +  yi    * linesize])
>                +   y *((1-x)*src[xi + (yi+1) * linesize] + x*src[xi + 1 + (yi+1) * linesize]);
>      }
> +    } else {
> +        xi = av_clipf(x, 0, w - 1);
> +        yi = av_clipf(y, 0, h - 1);

this should not drop precission to float
also possibly lrint() or something may be better than truncation for
nearest neighbor depending on definition of "nearest"

LGTM otherwise

Thanks


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Old school: Use the lowest level language in which you can solve the problem
            conveniently.
New school: Use the highest level language in which the latest supercomputer
            can solve the problem without the user falling asleep waiting.
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