lavfi/pad: add support to named options

doc/filters.texi

@@ -3725,14 +3725,50 @@ testsrc=s=100x100, split=4 [in0][in1][in2][in3];
 
 @section pad
 
-Add paddings to the input image, and places the original input at the
+Add paddings to the input image, and place the original input at the
 given coordinates @var{x}, @var{y}.
 
-It accepts the following parameters:
+The filter accepts parameters as a list of @var{key}=@var{value} pairs,
+separated by ":".
+
+If the key of the first options is omitted, the arguments are
+interpreted according to the syntax
 @var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
 
-The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
-expressions containing the following constants:
+A description of the accepted options follows.
+
+@table @option
+@item width, w
+@item height, h
+Specify an expression for the size of the output image with the
+paddings added. If the value for @var{width} or @var{height} is 0, the
+corresponding input size is used for the output.
+
+The @var{width} expression can reference the value set by the
+@var{height} expression, and vice versa.
+
+The default value of @var{width} and @var{height} is 0.
+
+@item x
+@item y
+Specify an expression for the offsets where to place the input image
+in the padded area with respect to the top/left border of the output
+image.
+
+The @var{x} expression can reference the value set by the @var{y}
+expression, and vice versa.
+
+The default value of @var{x} and @var{y} is 0.
+
+@item color
+Specify the color of the padded area, it can be the name of a color
+(case insensitive match) or a 0xRRGGBB[AA] sequence.
+
+The default value of @var{color} is "black".
+@end table
+
+The value for the @var{width}, @var{height}, @var{x}, and @var{y}
+options are expressions containing the following constants:
 
 @table @option
 @item in_w, in_h
@@ -3766,39 +3802,6 @@ horizontal and vertical chroma subsample values. For example for the
 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
 @end table
 
-Follows the description of the accepted parameters.
-
-@table @option
-@item width, height
-
-Specify the size of the output image with the paddings added. If the
-value for @var{width} or @var{height} is 0, the corresponding input size
-is used for the output.
-
-The @var{width} expression can reference the value set by the
-@var{height} expression, and vice versa.
-
-The default value of @var{width} and @var{height} is 0.
-
-@item x, y
-
-Specify the offsets where to place the input image in the padded area
-with respect to the top/left border of the output image.
-
-The @var{x} expression can reference the value set by the @var{y}
-expression, and vice versa.
-
-The default value of @var{x} and @var{y} is 0.
-
-@item color
-
-Specify the color of the padded area, it can be the name of a color
-(case insensitive match) or a 0xRRGGBB[AA] sequence.
-
-The default value of @var{color} is "black".
-
-@end table
-
 @subsection Examples
 
 @itemize
@@ -3810,6 +3813,11 @@ column 0, row 40:
 pad=640:480:0:40:violet
 @end example
 
+The example above is equivalent to the following command:
+@example
+pad=width=640:height=480:x=0:y=40:color=violet
+@end example
+
 @item
 Pad the input to get an output with dimensions increased by 3/2,
 and put the input video at the center of the padded area:

libavfilter/version.h

@@ -30,7 +30,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR  3
 #define LIBAVFILTER_VERSION_MINOR  35
-#define LIBAVFILTER_VERSION_MICRO 100
+#define LIBAVFILTER_VERSION_MICRO 101
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \

libavfilter/vf_pad.c

@@ -35,6 +35,7 @@
 #include "libavutil/colorspace.h"
 #include "libavutil/avassert.h"
 #include "libavutil/imgutils.h"
+#include "libavutil/opt.h"
 #include "libavutil/parseutils.h"
 #include "libavutil/mathematics.h"
 #include "drawutils.h"
@@ -76,40 +77,61 @@ static int query_formats(AVFilterContext *ctx)
 }
 
 typedef struct {
+    const AVClass *class;
     int w, h;               ///< output dimensions, a value of 0 will result in the input size
     int x, y;               ///< offsets of the input area with respect to the padded area
     int in_w, in_h;         ///< width and height for the padded input video, which has to be aligned to the chroma values in order to avoid chroma issues
 
-    char w_expr[256];       ///< width  expression string
-    char h_expr[256];       ///< height expression string
-    char x_expr[256];       ///< width  expression string
-    char y_expr[256];       ///< height expression string
-
+    char *w_expr;       ///< width  expression string
+    char *h_expr;       ///< height expression string
+    char *x_expr;       ///< width  expression string
+    char *y_expr;       ///< height expression string
+    char *color_str;
     uint8_t rgba_color[4];  ///< color for the padding area
     FFDrawContext draw;
     FFDrawColor color;
 } PadContext;
 
+#define OFFSET(x) offsetof(PadContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+
+static const AVOption pad_options[] = {
+    { "width",  "set the pad area width expression",       OFFSET(w_expr), AV_OPT_TYPE_STRING, {.str = "iw"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "w",      "set the pad area width expression",       OFFSET(w_expr), AV_OPT_TYPE_STRING, {.str = "iw"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "height", "set the pad area height expression",      OFFSET(h_expr), AV_OPT_TYPE_STRING, {.str = "ih"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "h",      "set the pad area height expression",      OFFSET(h_expr), AV_OPT_TYPE_STRING, {.str = "ih"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "x",      "set the x offset expression for the input image position", OFFSET(x_expr), AV_OPT_TYPE_STRING, {.str = "0"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "y",      "set the y offset expression for the input image position", OFFSET(y_expr), AV_OPT_TYPE_STRING, {.str = "0"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "color",  "set the color of the padded area border", OFFSET(color_str), AV_OPT_TYPE_STRING, {.str = "black"}, .flags = FLAGS },
+    {NULL}
+};
+
+AVFILTER_DEFINE_CLASS(pad);
+
 static av_cold int init(AVFilterContext *ctx, const char *args)
 {
     PadContext *pad = ctx->priv;
-    char color_string[128] = "black";
+    static const char *shorthand[] = { "width", "height", "x", "y", "color", NULL };
+    int ret;
 
-    av_strlcpy(pad->w_expr, "iw", sizeof(pad->w_expr));
-    av_strlcpy(pad->h_expr, "ih", sizeof(pad->h_expr));
-    av_strlcpy(pad->x_expr, "0" , sizeof(pad->w_expr));
-    av_strlcpy(pad->y_expr, "0" , sizeof(pad->h_expr));
+    pad->class = &pad_class;
+    av_opt_set_defaults(pad);
 
-    if (args)
-        sscanf(args, "%255[^:]:%255[^:]:%255[^:]:%255[^:]:%127s",
-               pad->w_expr, pad->h_expr, pad->x_expr, pad->y_expr, color_string);
+    if ((ret = av_opt_set_from_string(pad, args, shorthand, "=", ":")) < 0)
+        return ret;
 
-    if (av_parse_color(pad->rgba_color, color_string, -1, ctx) < 0)
+    if (av_parse_color(pad->rgba_color, pad->color_str, -1, ctx) < 0)
         return AVERROR(EINVAL);
 
     return 0;
 }
 
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    PadContext *pad = ctx->priv;
+    av_opt_free(pad);
+}
+
 static int config_input(AVFilterLink *inlink)
 {
     AVFilterContext *ctx = inlink->dst;
@@ -368,9 +390,11 @@ AVFilter avfilter_vf_pad = {
 
     .priv_size     = sizeof(PadContext),
     .init          = init,
+    .uninit        = uninit,
     .query_formats = query_formats,
 
     .inputs    = avfilter_vf_pad_inputs,
 
     .outputs   = avfilter_vf_pad_outputs,
+    .priv_class = &pad_class,
 };