[FFmpeg-devel] [PATCH 0/2] Extend delogo area to a superellipse

[FFmpeg-devel] [PATCH 0/2] Extend delogo area to a superellipse

[Jörg Habenicht via ffmpeg-devel]

Dear list,

with help from Michael I extended the ellipse area to a superellipse.

The user parameter 'r' has changed to become a float value.
Values 0 < r < 1 the area looks like a four edge star.
Value r = 1 the area get a rhombus.
Values 1 < r < 2 the area is a rhombus with concave sides.
Value r = 2 the area is an ellipse or a circle.
Values 2 < r the area looks like a rectangular with round edges.
Value = 0 (default, unset) the area is rectangular.

Because of the usage of math functions I added more code testing
the return values.

The parameter r=2 to get an ellipse delogo area seems non intuitive
to me. We should add a better description for the users of the
delogo filter.

The patch has been tested with 'make fate-rsync fate' rebased on the
master branch commit 268d0b6527cba1ebac1f44347578617341f85c35
and applies clean to my previous patchset "Patch to create a circular delogo
area"

Please have a look.

best regards
Jörg


Jörg Habenicht (2):
  avfilter/delogo: changed type of parameter 'r' to float
  avfilter/delogo: change delogo round area to superellipse area

 libavfilter/vf_delogo.c | 72 +++++++++++++++++++++++++++++++++--------
 1 file changed, 58 insertions(+), 14 deletions(-)

--
2.45.3

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[FFmpeg-devel] [PATCH 1/2] avfilter/delogo: changed type of parameter 'r' to float

[Jörg Habenicht via ffmpeg-devel]

Changed the type of the parameter 'r' from int to float. To be able to
flex the area as superellipse from rounded rectangle ('r' > 2.0) to a
concave shaped star ('r' < 1.0).
Check the input value to be 'r' >= 0.0, else error exit

Signed-off-by: Jörg Habenicht <j.habenicht@gmx.de>
---
 libavfilter/vf_delogo.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/libavfilter/vf_delogo.c b/libavfilter/vf_delogo.c
index fcf14d3e4f..60f16b309c 100644
--- a/libavfilter/vf_delogo.c
+++ b/libavfilter/vf_delogo.c
@@ -243,10 +243,11 @@ static void apply_delogo(uint8_t *dst, int dst_linesize,

 typedef struct DelogoContext {
     const AVClass *class;
-    int x, y, w, h, band, show, round;
-    char *x_expr, *y_expr, *w_expr, *h_expr;
-    AVExpr *x_pexpr, *y_pexpr, *w_pexpr, *h_pexpr;
+    int x, y, w, h, band, show;
+    char *x_expr, *y_expr, *w_expr, *h_expr, *r_expr;
+    AVExpr *x_pexpr, *y_pexpr, *w_pexpr, *h_pexpr, *r_pexpr;
     double var_values[VAR_VARS_NB];
+    double round;
 }  DelogoContext;

 #define OFFSET(x) offsetof(DelogoContext, x)
@@ -257,7 +258,7 @@ static const AVOption delogo_options[]= {
     { "y",    "set logo y position",       OFFSET(y_expr),    AV_OPT_TYPE_STRING, { .str = "-1" }, 0, 0, FLAGS },
     { "w",    "set logo width",            OFFSET(w_expr),    AV_OPT_TYPE_STRING, { .str = "-1" }, 0, 0, FLAGS },
     { "h",    "set logo height",           OFFSET(h_expr),    AV_OPT_TYPE_STRING, { .str = "-1" }, 0, 0, FLAGS },
-    { "r",    "logo is round/ellipse",     OFFSET(round),     AV_OPT_TYPE_BOOL,   { .i64 =  0 },   0, 1, FLAGS },
+    { "r",    "set superellipse parameter",OFFSET(r_expr),    AV_OPT_TYPE_STRING, { .str = "0" },  0, 0, FLAGS },
     { "show", "show delogo area",          OFFSET(show),      AV_OPT_TYPE_BOOL,   { .i64 =  0 },   0, 1, FLAGS },
     { NULL }
 };
@@ -271,6 +272,7 @@ static av_cold void uninit(AVFilterContext *ctx)
     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;
+    av_expr_free(s->r_pexpr);    s->r_pexpr = NULL;
 }

 static const enum AVPixelFormat pix_fmts[] = {
@@ -288,13 +290,15 @@ static av_cold int init(AVFilterContext *ctx)
     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 )
+        (ret = set_expr(&s->h_pexpr, s->h_expr, "h", ctx)) < 0 ||
+        (ret = set_expr(&s->r_pexpr, s->r_expr, "r", 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);
+    s->round = av_expr_eval(s->r_pexpr, s->var_values, s);

 #define CHECK_UNSET_OPT(opt)                                            \
     if (s->opt == -1) {                                            \
@@ -306,9 +310,14 @@ static av_cold int init(AVFilterContext *ctx)
     CHECK_UNSET_OPT(w);
     CHECK_UNSET_OPT(h);

+    if (s->round < 0.0) {
+        av_log(s, AV_LOG_ERROR, "Option r was set negative (r=%.2f).\n", s->round);
+        return AVERROR(EINVAL);
+    }
+
     s->band = 1;

-    av_log(ctx, AV_LOG_VERBOSE, "x:%d y:%d, w:%d h:%d band:%d round:%d show:%d\n",
+    av_log(ctx, AV_LOG_VERBOSE, "x:%d y:%d, w:%d h:%d band:%d round:%f show:%d\n",
            s->x, s->y, s->w, s->h, s->band, s->round, s->show);

     s->w += s->band*2;
--
2.45.3

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[FFmpeg-devel] [PATCH 2/2] avfilter/delogo: change delogo round area to superellipse area

[Jörg Habenicht via ffmpeg-devel]

Changed the delogo area to a definition of a superellipse. See here
https://en.wikipedia.org/wiki/Superellipse
Changed the meaning of the parameter 'r'.
'r' = 0.0 resolves to a rectangular area.
0 <'r' < 1 resolves to a star with concave sides.
'r' = 1.0 resolves to a rhombus.
1 < 'r' < 2 resolves to a rhombus with convex sides.
'r' = 2.0 resolves to an ellipse or a circel.
2 < 'r' resolves to something like a rectangle with round corners.
Unset is the default of 'r' = 0.0 .

Signed-off-by: Jörg Habenicht <j.habenicht@gmx.de>
---
 libavfilter/vf_delogo.c | 51 ++++++++++++++++++++++++++++++++++-------
 1 file changed, 43 insertions(+), 8 deletions(-)

diff --git a/libavfilter/vf_delogo.c b/libavfilter/vf_delogo.c
index 60f16b309c..ed81d112e2 100644
--- a/libavfilter/vf_delogo.c
+++ b/libavfilter/vf_delogo.c
@@ -90,7 +90,7 @@ static int set_expr(AVExpr **pexpr, const char *expr, const char *option, void *
  * @param logo_w width of the logo
  * @param logo_h height of the logo
  * @param band   the size of the band around the processed area
- * @param round  whether delogo is applied to a rectangular or round area
+ * @param round  parameter of superellipse, 0==rectanglar, 1.0==rhombus, 2.0==circular/ellipse
  * @param show   show a rectangle around the processed area, useful for
  *               parameters tweaking
  * @param direct if non-zero perform in-place processing
@@ -99,7 +99,7 @@ static void apply_delogo(uint8_t *dst, int dst_linesize,
                          uint8_t *src, int src_linesize,
                          int w, int h, AVRational sar,
                          int logo_x, int logo_y, int logo_w, int logo_h,
-                         unsigned int band, int round, int show, int direct)
+                         unsigned int band, double round, int show, int direct)
 {
     /* Round area algorithm description:
      *
@@ -123,6 +123,18 @@ static void apply_delogo(uint8_t *dst, int dst_linesize,
      *
      * px is later defined x, py defined y.
      * logo_w is later defined logo_w2, logo_h defined logo_h2.
+     *
+     * A point inside a superellipse is defined as x^n / a^n + y^n / b^n = 1
+     * <=> (x + logo_x)^n / (logo_w / 2)^n
+     *     + (y + logo_y)^n / (logo_h / 2)^n <= 1
+     * <=> (px - logo_x - a + logo_x)^n / (logo_w / 2)^n
+     *     + (py - logo_y - b + logo_y)^n / (logo_h / 2)^n <= 1
+     * <=> (px - a)^n / (logo_w / 2)^n
+     *     + (py - b)^n / (logo_h / 2)^n <= 1
+     * <=> ((px - a) / (logo_w / 2))^n
+     *     + ((py - b) / (logo_h / 2))^n <= 1
+     *
+     * n is defined by the parameter 'round'
      */

     int x, y;
@@ -149,7 +161,7 @@ static void apply_delogo(uint8_t *dst, int dst_linesize,
     topright = src+logo_y1 * src_linesize+logo_x2;
     botleft  = src+logo_y2 * src_linesize+logo_x1;

-    if (round) {
+    if (round > 0.0) {
         logo_w2 = (logo_x2 - logo_x1) / 2.0;
         logo_h2 = (logo_y2 - logo_y1) / 2.0;
         a = logo_x1 + logo_w2;
@@ -180,17 +192,40 @@ static void apply_delogo(uint8_t *dst, int dst_linesize,
                 continue;
             }

-            if (round) {
+            if (round > 0.0) {
                 double xf, yf;
                 /* Evaluate if x,y is inside the ellipse, else continue
                  * This is the calculation
-                 *      (px - a)^2 / (logo_w / 2)^2 +
-                 *      (py - b)^2 / (logo_h / 2)^2 <= 1
+                 *      (px - a)^n / (logo_w / 2)^n +
+                 *      (py - b)^n / (logo_h / 2)^n <= 1
                  */
+                errno = 0;
                 xf = ((double)x - a) / logo_w2;
-                xf *= xf;
+                xf = fabs(xf); // use positive values only, analog to xf^2
+                xf = pow(xf, round);
+                if (isnan(xf)) {
+                    av_log(NULL, AV_LOG_ERROR,
+                           "Error in delogo calculating ellipse value. NAN value returned\n");
+                    return;
+                }
+                if (errno) {
+                    av_log(NULL, AV_LOG_ERROR,
+                           "Error in delogo calculating ellipse value. Math error returned\n");
+                    return;
+                }
                 yf = ((double)y - b) / logo_h2;
-                yf *= yf;
+                yf = fabs(yf); // use positive values only, analog to yf^2
+                yf = pow(yf, round);
+                if (isnan(xf)) {
+                    av_log(NULL, AV_LOG_ERROR,
+                           "Error in delogo calculating ellipse value. NAN value returned\n");
+                    return;
+                }
+                if (errno) {
+                    av_log(NULL, AV_LOG_ERROR,
+                           "Error in delogo calculating ellipse value. Math error returned\n");
+                    return;
+                }
                 if (xf + yf > 1.0)
                     continue;
             }
--
2.45.3

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