avfilter/vf_delogo: support expr in delogo filter

Signed-off-by: Steven Liu <lq@chinaffmpeg.org>

libavfilter/vf_delogo.c

@@ -31,10 +31,52 @@
 #include "libavutil/imgutils.h"
 #include "libavutil/opt.h"
 #include "libavutil/pixdesc.h"
+#include "libavutil/eval.h"
 #include "avfilter.h"
 #include "formats.h"
 #include "internal.h"
 #include "video.h"
+static const char * const var_names[] = {
+    "x",
+    "y",
+    "w",
+    "h",
+    "n",            ///< number of frame
+    "t",            ///< timestamp expressed in seconds
+    NULL
+};
+
+enum var_name {
+    VAR_X,
+    VAR_Y,
+    VAR_W,
+    VAR_H,
+    VAR_N,
+    VAR_T,
+    VAR_VARS_NB
+};
+#define TS2T(ts, tb) ((ts) == AV_NOPTS_VALUE ? NAN : (double)(ts) * av_q2d(tb))
+
+static int set_expr(AVExpr **pexpr, const char *expr, const char *option, void *log_ctx)
+{
+    int ret;
+    AVExpr *old = NULL;
+
+    if (*pexpr)
+        old = *pexpr;
+    ret = av_expr_parse(pexpr, expr, var_names, NULL, NULL, NULL, NULL, 0, log_ctx);
+    if (ret < 0) {
+        av_log(log_ctx, AV_LOG_ERROR,
+               "Error when parsing the expression '%s' for %s\n",
+               expr, option);
+        *pexpr = old;
+        return ret;
+    }
+
+    av_expr_free(old);
+    return 0;
+}
+
 
 /**
  * Apply a simple delogo algorithm to the image in src and put the
@@ -156,16 +198,19 @@ static void apply_delogo(uint8_t *dst, int dst_linesize,
 typedef struct DelogoContext {
     const AVClass *class;
     int x, y, w, h, band, show;
+    char *x_expr, *y_expr, *w_expr, *h_expr;
+    AVExpr *x_pexpr, *y_pexpr, *w_pexpr, *h_pexpr;
+    double var_values[VAR_VARS_NB];
 }  DelogoContext;
 
 #define OFFSET(x) offsetof(DelogoContext, x)
 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
 
 static const AVOption delogo_options[]= {
-    { "x",    "set logo x position",       OFFSET(x),    AV_OPT_TYPE_INT, { .i64 = -1 }, -1, INT_MAX, FLAGS },
+    { "x",    "set logo x position",       OFFSET(x_expr),    AV_OPT_TYPE_STRING, { .str = "-1" }, CHAR_MIN, CHAR_MAX, FLAGS },
-    { "y",    "set logo y position",       OFFSET(y),    AV_OPT_TYPE_INT, { .i64 = -1 }, -1, INT_MAX, FLAGS },
+    { "y",    "set logo y position",       OFFSET(y_expr),    AV_OPT_TYPE_STRING, { .str = "-1" }, CHAR_MIN, CHAR_MAX, FLAGS },
-    { "w",    "set logo width",            OFFSET(w),    AV_OPT_TYPE_INT, { .i64 = -1 }, -1, INT_MAX, FLAGS },
+    { "w",    "set logo width",            OFFSET(w_expr),    AV_OPT_TYPE_STRING, { .str = "-1" }, CHAR_MIN, CHAR_MAX, FLAGS },
-    { "h",    "set logo height",           OFFSET(h),    AV_OPT_TYPE_INT, { .i64 = -1 }, -1, INT_MAX, FLAGS },
+    { "h",    "set logo height",           OFFSET(h_expr),    AV_OPT_TYPE_STRING, { .str = "-1" }, CHAR_MIN, CHAR_MAX, FLAGS },
 #if LIBAVFILTER_VERSION_MAJOR < 7
     /* Actual default value for band/t is 1, set in init */
     { "band", "set delogo area band size", OFFSET(band), AV_OPT_TYPE_INT, { .i64 =  0 },  0, INT_MAX, FLAGS },
@@ -176,6 +221,16 @@ static const AVOption delogo_options[]= {
 };
 
 AVFILTER_DEFINE_CLASS(delogo);
+static void uninit(AVFilterContext *ctx)
+{
+    DelogoContext *s = ctx->priv;
+
+    av_expr_free(s->x_pexpr);    s->x_pexpr = NULL;
+    av_expr_free(s->y_pexpr);    s->y_pexpr = NULL;
+    av_expr_free(s->w_pexpr);    s->w_pexpr = NULL;
+    av_expr_free(s->h_pexpr);    s->h_pexpr = NULL;
+}
+
 
 static int query_formats(AVFilterContext *ctx)
 {
@@ -194,6 +249,18 @@ static int query_formats(AVFilterContext *ctx)
 static av_cold int init(AVFilterContext *ctx)
 {
     DelogoContext *s = ctx->priv;
+    int ret = 0;
+
+    if ((ret = set_expr(&s->x_pexpr, s->x_expr, "x", ctx)) < 0 ||
+        (ret = set_expr(&s->y_pexpr, s->y_expr, "y", ctx)) < 0 ||
+        (ret = set_expr(&s->w_pexpr, s->w_expr, "w", ctx)) < 0 ||
+        (ret = set_expr(&s->h_pexpr, s->h_expr, "h", ctx)) < 0 )
+        return ret;
+
+    s->x = av_expr_eval(s->x_pexpr, s->var_values, s);
+    s->y = av_expr_eval(s->y_pexpr, s->var_values, s);
+    s->w = av_expr_eval(s->w_pexpr, s->var_values, s);
+    s->h = av_expr_eval(s->h_pexpr, s->var_values, s);
 
 #define CHECK_UNSET_OPT(opt)                                            \
     if (s->opt == -1) {                                            \
@@ -252,6 +319,13 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
     int plane;
     AVRational sar;
 
+    s->var_values[VAR_N] = inlink->frame_count_out;
+    s->var_values[VAR_T] = TS2T(in->pts, inlink->time_base);
+    s->x = av_expr_eval(s->x_pexpr, s->var_values, s);
+    s->y = av_expr_eval(s->y_pexpr, s->var_values, s);
+    s->w = av_expr_eval(s->w_pexpr, s->var_values, s);
+    s->h = av_expr_eval(s->h_pexpr, s->var_values, s);
+
     if (av_frame_is_writable(in)) {
         direct = 1;
         out = in;
@@ -317,6 +391,7 @@ AVFilter ff_vf_delogo = {
     .priv_size     = sizeof(DelogoContext),
     .priv_class    = &delogo_class,
     .init          = init,
+    .uninit        = uninit,
     .query_formats = query_formats,
     .inputs        = avfilter_vf_delogo_inputs,
     .outputs       = avfilter_vf_delogo_outputs,