[PATCH] Make the crop filter accept parametric expressions.
Stefano Sabatini
stefano.sabatini-lala
Thu Sep 9 01:05:04 CEST 2010
---
doc/filters.texi | 63 ++++++++++++++++++++++++------
libavfilter/vf_crop.c | 105 ++++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 151 insertions(+), 17 deletions(-)
diff --git a/doc/filters.texi b/doc/filters.texi
index 60ecf56..e0627dd 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -28,32 +28,71 @@ Below is a description of the currently available video filters.
Crop the input video to @var{x}:@var{y}:@var{width}:@var{height}.
- at example
-./ffmpeg -i in.avi -vf "crop=0:0:0:240" out.avi
- at end example
+The parameters are expressions containing the following constants:
- at var{x} and @var{y} specify the position of the top-left corner of the
-output (non-cropped) area.
+ at table @option
+ at item E, PI, PHI
+the corresponding mathematical approximated values for e
+(euler number), pi (greek PI), PHI (golden ratio)
-The default value of @var{x} and @var{y} is 0.
+ at item TB
+the input timebase used for the timestamps
+
+ at item w, h
+the input width and heigth.
-The @var{width} and @var{height} parameters specify the width and height
-of the output (non-cropped) area.
+ at item x, y
+the computed values for @var{x} and @var{y}.
+
+ at item n
+the number of input frame, starting from 0
+
+ at item pos
+the position in the file of the input frame, -1 if unknown
-A value of 0 is interpreted as the maximum possible size contained in
-the area delimited by the top-left corner at position x:y.
+ at item pts
+presentation time stamp of the input frame, expressed in TB units
+
+ at end table
+
+ at var{x} and @var{y} specify the expressions for the 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} and @var{y} is "0".
+
+The @var{width} and @var{height} parameters specify the expressions for
+the width and height of the output (non-cropped) area. They are
+evaluated just at the configuration of the filter.
+
+The default value of @var{width} is "w-x", and the default value of
+ at var{height} is "h-y", which specify the maximum possible size
+contained in the area delimited by the top-left corner at position
+x:y.
For example the parameters:
@example
-"crop=100:100:0:0"
+"crop=100:100"
@end example
will delimit the rectangle with the top-left corner placed at position
100:100 and the right-bottom corner corresponding to the right-bottom
corner of the input image.
-The default value of @var{width} and @var{height} is 0.
+Follow other examples:
+ at example
+# crop 10 pixels from the lefth and right borders, and 20 pixels from
+# the top and bottom borders
+crop=10:20:w-2*x:h-2*y
+
+# keep only the bottom right quarter of the input image
+crop=w/2:h/2
+
+# trembling effect
+crop='10+10*sin(n/10):20+20*sin(n/5):w-2*x:h-2*y
+ at end example
@section fifo
diff --git a/libavfilter/vf_crop.c b/libavfilter/vf_crop.c
index 880c954..e8c0235 100644
--- a/libavfilter/vf_crop.c
+++ b/libavfilter/vf_crop.c
@@ -24,8 +24,40 @@
*/
#include "avfilter.h"
+#include "libavutil/eval.h"
+#include "libavutil/avstring.h"
#include "libavcore/imgutils.h"
+static const char *var_names[] = {
+ "E",
+ "PHI",
+ "PI",
+ "TB", ///< timebase
+ "x",
+ "y",
+ "w", ///< width of the input video
+ "h", ///< height of the input video
+ "n", ///< number of frame
+ "pos", ///< position in the file
+ "pts", ///< presentation time stamp
+ NULL
+};
+
+enum var_name {
+ E,
+ PHI,
+ PI,
+ TB,
+ X,
+ Y,
+ W,
+ H,
+ N,
+ POS,
+ PTS,
+ VARS_NB
+};
+
typedef struct {
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
@@ -34,6 +66,9 @@ 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], w_expr[256], h_expr[256];
+ AVExpr *x_pexpr, *y_pexpr; /* parsed expressions for x and y */
+ double var_values[VARS_NB];
} CropContext;
static int query_formats(AVFilterContext *ctx)
@@ -72,8 +107,13 @@ static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
{
CropContext *crop = ctx->priv;
+ av_strlcpy(crop->x_expr, "0" , sizeof(crop->x_expr));
+ av_strlcpy(crop->y_expr, "0" , sizeof(crop->y_expr));
+ av_strlcpy(crop->w_expr, "w-x", sizeof(crop->w_expr));
+ av_strlcpy(crop->h_expr, "h-y", sizeof(crop->h_expr));
+
if (args)
- sscanf(args, "%d:%d:%d:%d", &crop->x, &crop->y, &crop->w, &crop->h);
+ sscanf(args, "%255[^:]:%255[^:]:%255[^:]:%255[^:]", crop->x_expr, crop->y_expr, crop->w_expr, crop->h_expr);
return 0;
}
@@ -83,18 +123,43 @@ static int config_input(AVFilterLink *link)
AVFilterContext *ctx = link->dst;
CropContext *crop = ctx->priv;
const AVPixFmtDescriptor *pix_desc = &av_pix_fmt_descriptors[link->format];
+ int ret;
+ const char *expr;
+ double res;
+
+ crop->var_values[E ] = M_E;
+ crop->var_values[PHI] = M_PHI;
+ crop->var_values[PI ] = M_PI;
+ crop->var_values[TB ] = AV_TIME_BASE;
+ crop->var_values[W ] = ctx->inputs[0]->w;
+ crop->var_values[H ] = ctx->inputs[0]->h;
+ crop->var_values[N ] = 0;
av_image_fill_max_pixsteps(crop->max_step, NULL, pix_desc);
crop->hsub = av_pix_fmt_descriptors[link->format].log2_chroma_w;
crop->vsub = av_pix_fmt_descriptors[link->format].log2_chroma_h;
- if (crop->w == 0)
- crop->w = link->w - crop->x;
- if (crop->h == 0)
- crop->h = link->h - crop->y;
+ if ((ret = av_parse_expr(&crop->x_pexpr, crop->x_expr, var_names,
+ NULL, NULL, NULL, NULL, 0, ctx)) < 0 ||
+ (ret = av_parse_expr(&crop->y_pexpr, crop->y_expr, var_names,
+ NULL, NULL, NULL, NULL, 0, ctx)) < 0)
+ return AVERROR(EINVAL);
+ crop->x = av_eval_expr(crop->x_pexpr, crop->var_values, NULL);
+ crop->y = av_eval_expr(crop->y_pexpr, crop->var_values, NULL);
crop->x &= ~((1 << crop->hsub) - 1);
crop->y &= ~((1 << crop->vsub) - 1);
+ crop->var_values[X] = crop->x;
+ crop->var_values[Y] = crop->y;
+
+#define PARSE_AND_EVAL(var, var_expr) \
+ if ((ret = av_parse_and_eval_expr(&res, (expr = var_expr), var_names, crop->var_values, \
+ NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0) \
+ goto fail_expr; \
+ var = res;
+
+ PARSE_AND_EVAL(crop->w, crop->w_expr);
+ PARSE_AND_EVAL(crop->h, crop->h_expr);
av_log(link->dst, AV_LOG_INFO, "x:%d y:%d w:%d h:%d\n",
crop->x, crop->y, crop->w, crop->h);
@@ -110,6 +175,11 @@ static int config_input(AVFilterLink *link)
}
return 0;
+
+fail_expr:
+ av_log(NULL, AV_LOG_ERROR,
+ "Error when evaluating the expression '%s'\n", expr);
+ return ret;
}
static int config_output(AVFilterLink *link)
@@ -131,6 +201,22 @@ static void start_frame(AVFilterLink *link, AVFilterBufferRef *picref)
picref->video->w = crop->w;
picref->video->h = crop->h;
+ crop->var_values[PTS] = picref->pts;
+ crop->var_values[POS] = picref->pos;
+ crop->x = crop->var_values[X] = av_eval_expr(crop->x_pexpr, crop->var_values, NULL);
+ crop->y = crop->var_values[Y] = av_eval_expr(crop->y_pexpr, crop->var_values, NULL);
+
+ if (crop->x < 0) crop->x = 0;
+ if (crop->y < 0) crop->y = 0;
+ if ((unsigned)crop->x + (unsigned)crop->w > link->w) crop->x = link->w - crop->w;
+ if ((unsigned)crop->y + (unsigned)crop->h > link->h) crop->y = link->h - crop->y;
+ crop->x &= ~((1 << crop->hsub) - 1);
+ crop->y &= ~((1 << crop->vsub) - 1);
+
+ av_log(link->dst, AV_LOG_DEBUG,
+ "x:%d y:%d x+w:%d y+h:%d\n",
+ crop->x, crop->y, crop->x+crop->w, crop->y+crop->h);
+
ref2->data[0] += crop->y * ref2->linesize[0];
ref2->data[0] += (crop->x * crop->max_step[0]);
@@ -170,6 +256,14 @@ static void draw_slice(AVFilterLink *link, int y, int h, int slice_dir)
avfilter_draw_slice(ctx->outputs[0], y - crop->y, h, slice_dir);
}
+static void end_frame(AVFilterLink *link)
+{
+ CropContext *crop = link->dst->priv;
+
+ crop->var_values[N] += 1.0;
+ avfilter_end_frame(link->dst->outputs[0]);
+}
+
AVFilter avfilter_vf_crop = {
.name = "crop",
.description = NULL_IF_CONFIG_SMALL("Crop the input video to x:y:width:height."),
@@ -183,6 +277,7 @@ AVFilter avfilter_vf_crop = {
.type = AVMEDIA_TYPE_VIDEO,
.start_frame = start_frame,
.draw_slice = draw_slice,
+ .end_frame = end_frame,
.get_video_buffer = avfilter_null_get_video_buffer,
.config_props = config_input, },
{ .name = NULL}},
--
1.7.1
--J/dobhs11T7y2rNN--
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