lavfi/crop: add support to option parsing

Also fix documentation accordingly.

doc/filters.texi

@@ -1518,11 +1518,40 @@ testing purposes.
 
 @section crop
 
-Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}
+Crop the input video.
 
-The @var{keep_aspect} parameter is optional, if specified and set to a
+This filter accepts a list of @var{key}=@var{value} pairs as argument,
-non-zero value will force the output display aspect ratio to be the
+separated by ':'. If the key of the first options is omitted, the
-same of the input, by changing the output sample aspect ratio.
+arguments are interpreted according to the syntax
+@var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}.
+
+A description of the accepted options follows:
+@table @option
+@item w, out_w
+Set the crop area width. It defaults to @code{iw}.
+This expression is evaluated only once during the filter
+configuration.
+
+@item h, out_h
+Set the crop area width. It defaults to @code{ih}.
+This expression is evaluated only once during the filter
+configuration.
+
+@item x
+Set the expression for the x top-left coordinate of the cropped area.
+It defaults to @code{(in_w-out_w)/2}.
+This expression is evaluated per-frame.
+
+@item y
+Set the expression for the y top-left coordinate of the cropped area.
+It defaults to @code{(in_h-out_h)/2}.
+This expression is evaluated per-frame.
+
+@item keep_aspect
+If set to 1 will force the output display aspect ratio
+to be the same of the input, by changing the output sample aspect
+ratio. It defaults to 0.
+@end table
 
 The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are
 expressions containing the following constants:
@@ -1568,13 +1597,6 @@ timestamp expressed in seconds, NAN if the input timestamp is unknown
 
 @end table
 
-The @var{out_w} and @var{out_h} parameters specify the expressions for
-the width and height of the output (cropped) video. They are
-evaluated just at the configuration of the filter.
-
-The default value of @var{out_w} is "in_w", and the default value of
-@var{out_h} is "in_h".
-
 The expression for @var{out_w} may depend on the value of @var{out_h},
 and the expression for @var{out_h} may depend on @var{out_w}, but they
 cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
@@ -1585,10 +1607,6 @@ position of the top-left corner of the output (non-cropped) area. They
 are evaluated for each frame. If the evaluated value is not valid, it
 is approximated to the nearest valid value.
 
-The default value of @var{x} is "(in_w-out_w)/2", and the default
-value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
-the center of the input image.
-
 The expression for @var{x} may depend on @var{y}, and the expression
 for @var{y} may depend on @var{x}.
 

libavfilter/version.h

@@ -30,7 +30,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR  3
 #define LIBAVFILTER_VERSION_MINOR  27
-#define LIBAVFILTER_VERSION_MICRO 101
+#define LIBAVFILTER_VERSION_MICRO 102
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \

libavfilter/vf_crop.c

@@ -37,6 +37,7 @@
 #include "libavutil/libm.h"
 #include "libavutil/imgutils.h"
 #include "libavutil/mathematics.h"
+#include "libavutil/opt.h"
 
 static const char *const var_names[] = {
     "in_w", "iw",   ///< width  of the input video
@@ -75,6 +76,7 @@ enum var_name {
 };
 
 typedef struct {
+    const AVClass *class;
     int  x;             ///< x offset of the non-cropped area with respect to the input area
     int  y;             ///< y offset of the non-cropped area with respect to the input area
     int  w;             ///< width of the cropped area
@@ -85,11 +87,44 @@ typedef struct {
 
     int max_step[4];    ///< max pixel step for each plane, expressed as a number of bytes
     int hsub, vsub;     ///< chroma subsampling
-    char x_expr[256], y_expr[256], ow_expr[256], oh_expr[256];
+    char *x_expr, *y_expr, *w_expr, *h_expr;
     AVExpr *x_pexpr, *y_pexpr;  /* parsed expressions for x and y */
     double var_values[VAR_VARS_NB];
 } CropContext;
 
+#define OFFSET(x) offsetof(CropContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+
+static const AVOption crop_options[] = {
+    { "x",           "set the x crop area expression",       OFFSET(x_expr), AV_OPT_TYPE_STRING, {.str = "(in_w-out_w)/2"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "y",           "set the y crop area expression",       OFFSET(y_expr), AV_OPT_TYPE_STRING, {.str = "(in_h-out_h)/2"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "out_w",       "set the width crop area expression",   OFFSET(w_expr), AV_OPT_TYPE_STRING, {.str = "iw"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "w",           "set the width crop area expression",   OFFSET(w_expr), AV_OPT_TYPE_STRING, {.str = "iw"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "out_h",       "set the height crop area expression",  OFFSET(h_expr), AV_OPT_TYPE_STRING, {.str = "ih"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "h",           "set the height crop area expression",  OFFSET(h_expr), AV_OPT_TYPE_STRING, {.str = "ih"}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "keep_aspect", "force packed RGB in input and output", OFFSET(keep_aspect), AV_OPT_TYPE_INT, {.i64=0}, 0, 1, FLAGS },
+    {NULL}
+};
+
+AVFILTER_DEFINE_CLASS(crop);
+
+static av_cold int init(AVFilterContext *ctx, const char *args)
+{
+    CropContext *crop = ctx->priv;
+    static const char *shorthand[] = { "w", "h", "x", "y", "keep_aspect", NULL };
+
+    crop->class = &crop_class;
+    av_opt_set_defaults(crop);
+
+    return av_opt_set_from_string(crop, args, shorthand, "=", ":");
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    CropContext *crop = ctx->priv;
+    av_opt_free(crop);
+}
+
 static int query_formats(AVFilterContext *ctx)
 {
     static const enum AVPixelFormat pix_fmts[] = {
@@ -123,29 +158,6 @@ static int query_formats(AVFilterContext *ctx)
     return 0;
 }
 
-static av_cold int init(AVFilterContext *ctx, const char *args)
-{
-    CropContext *crop = ctx->priv;
-
-    av_strlcpy(crop->ow_expr, "iw", sizeof(crop->ow_expr));
-    av_strlcpy(crop->oh_expr, "ih", sizeof(crop->oh_expr));
-    av_strlcpy(crop->x_expr, "(in_w-out_w)/2", sizeof(crop->x_expr));
-    av_strlcpy(crop->y_expr, "(in_h-out_h)/2", sizeof(crop->y_expr));
-
-    if (args)
-        sscanf(args, "%255[^:]:%255[^:]:%255[^:]:%255[^:]:%d", crop->ow_expr, crop->oh_expr, crop->x_expr, crop->y_expr, &crop->keep_aspect);
-
-    return 0;
-}
-
-static av_cold void uninit(AVFilterContext *ctx)
-{
-    CropContext *crop = ctx->priv;
-
-    av_expr_free(crop->x_pexpr); crop->x_pexpr = NULL;
-    av_expr_free(crop->y_pexpr); crop->y_pexpr = NULL;
-}
-
 static inline int normalize_double(int *n, double d)
 {
     int ret = 0;
@@ -189,16 +201,16 @@ static int config_input(AVFilterLink *link)
     crop->hsub = pix_desc->log2_chroma_w;
     crop->vsub = pix_desc->log2_chroma_h;
 
-    if ((ret = av_expr_parse_and_eval(&res, (expr = crop->ow_expr),
+    if ((ret = av_expr_parse_and_eval(&res, (expr = crop->w_expr),
                                       var_names, crop->var_values,
                                       NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0) goto fail_expr;
     crop->var_values[VAR_OUT_W] = crop->var_values[VAR_OW] = res;
-    if ((ret = av_expr_parse_and_eval(&res, (expr = crop->oh_expr),
+    if ((ret = av_expr_parse_and_eval(&res, (expr = crop->h_expr),
                                       var_names, crop->var_values,
                                       NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0) goto fail_expr;
     crop->var_values[VAR_OUT_H] = crop->var_values[VAR_OH] = res;
     /* evaluate again ow as it may depend on oh */
-    if ((ret = av_expr_parse_and_eval(&res, (expr = crop->ow_expr),
+    if ((ret = av_expr_parse_and_eval(&res, (expr = crop->w_expr),
                                       var_names, crop->var_values,
                                       NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0) goto fail_expr;
     crop->var_values[VAR_OUT_W] = crop->var_values[VAR_OW] = res;
@@ -207,7 +219,7 @@ static int config_input(AVFilterLink *link)
         av_log(ctx, AV_LOG_ERROR,
                "Too big value or invalid expression for out_w/ow or out_h/oh. "
                "Maybe the expression for out_w:'%s' or for out_h:'%s' is self-referencing.\n",
-               crop->ow_expr, crop->oh_expr);
+               crop->w_expr, crop->h_expr);
         return AVERROR(EINVAL);
     }
     crop->w &= ~((1 << crop->hsub) - 1);
@@ -348,4 +360,5 @@ AVFilter avfilter_vf_crop = {
 
     .inputs    = avfilter_vf_crop_inputs,
     .outputs   = avfilter_vf_crop_outputs,
+    .priv_class = &crop_class,
 };