vf_pad: switch to an AVOptions-based system.

doc/filters.texi

@@ -1546,8 +1546,38 @@ approach is yet to be tested.
 Add paddings to the input image, and places the original input at the
 given coordinates @var{x}, @var{y}.
 
-It accepts the following parameters:
-@var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
+This filter accepts the following 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
 
 The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
 expressions containing the following constants:
@@ -1582,46 +1612,13 @@ 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
-
 Some examples follow:
 
 @example
 # Add paddings with color "violet" to the input video. Output video
 # size is 640x480, the top-left corner of the input video is placed at
 # column 0, row 40.
-pad=640:480:0:40:violet
+pad=width=640:height=480:x=0:y=40:color=violet
 
 # pad the input to get an output with dimensions increased bt 3/2,
 # and put the input video at the center of the padded area

libavfilter/vf_pad.c

@@ -37,6 +37,8 @@
 #include "libavutil/imgutils.h"
 #include "libavutil/parseutils.h"
 #include "libavutil/mathematics.h"
+#include "libavutil/opt.h"
+
 #include "drawutils.h"
 
 static const char *const var_names[] = {
@@ -93,14 +95,16 @@ 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 color[4];       ///< color expressed either in YUVA or RGBA colorspace for the padding area
     uint8_t *line[4];
@@ -111,18 +115,8 @@ typedef struct {
 static av_cold int init(AVFilterContext *ctx, const char *args)
 {
     PadContext *pad = ctx->priv;
-    char color_string[128] = "black";
-
-    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));
 
-    if (args)
-        sscanf(args, "%255[^:]:%255[^:]:%255[^:]:%255[^:]:%255s",
-               pad->w_expr, pad->h_expr, pad->x_expr, pad->y_expr, color_string);
-
-    if (av_parse_color(pad->color, color_string, -1, ctx) < 0)
+    if (av_parse_color(pad->color, pad->color_str, -1, ctx) < 0)
         return AVERROR(EINVAL);
 
     return 0;
@@ -413,6 +407,26 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
     return ff_filter_frame(inlink->dst->outputs[0], out);
 }
 
+#define OFFSET(x) offsetof(PadContext, x)
+#define FLAGS AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption options[] = {
+    { "width",  "Output video width",       OFFSET(w_expr),    AV_OPT_TYPE_STRING, { .str = "iw" },    .flags = FLAGS },
+    { "height", "Output video height",      OFFSET(h_expr),    AV_OPT_TYPE_STRING, { .str = "ih" },    .flags = FLAGS },
+    { "x",      "Horizontal position of the left edge of the input video in the "
+        "output video",                     OFFSET(x_expr),    AV_OPT_TYPE_STRING, { .str = "0"  },    .flags = FLAGS },
+    { "y",      "Vertical position of the top edge of the input video in the "
+        "output video",                     OFFSET(y_expr),    AV_OPT_TYPE_STRING, { .str = "0"  },    .flags = FLAGS },
+    { "color",  "Color of the padded area", OFFSET(color_str), AV_OPT_TYPE_STRING, { .str = "black" }, .flags = FLAGS },
+    { NULL },
+};
+
+static const AVClass pad_class = {
+    .class_name = "pad",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
 static const AVFilterPad avfilter_vf_pad_inputs[] = {
     {
         .name             = "default",
@@ -438,6 +452,7 @@ AVFilter avfilter_vf_pad = {
     .description   = NULL_IF_CONFIG_SMALL("Pad input image to width:height[:x:y[:color]] (default x and y: 0, default color: black)."),
 
     .priv_size     = sizeof(PadContext),
+    .priv_class    = &pad_class,
     .init          = init,
     .uninit        = uninit,
     .query_formats = query_formats,