@@ -5750,6 +5750,8 @@ options. In this case, the unset component(s) will fallback on this

 @option{all} setting.

 @item psfile

 Specify a Photoshop curves file (@code{.acv}) to import the settings from.

+@item plot

+Save Gnuplot script of the curves in specified file.

 @end table

 To avoid some filtergraph syntax conflicts, each key points list need to be

@@ -5796,6 +5798,14 @@ Use a Photoshop preset and redefine the points of the green component:

 @example

 curves=psfile='MyCurvesPresets/purple.acv':green='0/0 0.45/0.53 1/1'

 @end example

+

+@item

+Check out the curves of the @code{cross_process} profile using @command{ffmpeg}

+and @command{gnuplot}:

+@example

+ffmpeg -f lavfi -i color -vf curves=cross_process:plot=/tmp/curves.plt -frames:v 1 -f null -

+gnuplot -p /tmp/curves.plt

+@end example

 @end itemize

 @section datascope

@@ -67,6 +67,7 @@ typedef struct {

     char *psfile;

     uint8_t rgba_map[4];

     int step;

+    char *plot_filename;

 } CurvesContext;

 typedef struct ThreadData {

@@ -98,6 +99,7 @@ static const AVOption curves_options[] = {

     { "b",     "set blue points coordinates",  OFFSET(comp_points_str[2]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },

     { "all",   "set points coordinates for all components", OFFSET(comp_points_str_all), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },

     { "psfile", "set Photoshop curves file name", OFFSET(psfile), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },

+    { "plot", "save Gnuplot script of the curves in specified file", OFFSET(plot_filename), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },

     { NULL }

 };

@@ -377,6 +379,65 @@ end:

     return ret;

 }

+static int dump_curves(const char *fname, uint8_t graph[NB_COMP + 1][256],

+                       struct keypoint *comp_points[NB_COMP + 1])

+{

+    int i;

+    AVBPrint buf;

+    static const char * const colors[] = { "red", "green", "blue", "#404040", };

+    FILE *f = av_fopen_utf8(fname, "w");

+

+    av_assert0(FF_ARRAY_ELEMS(colors) == NB_COMP + 1);

+

+    if (!f) {

+        int ret = AVERROR(errno);

+        av_log(NULL, AV_LOG_ERROR, "Cannot open file '%s' for writing: %s\n",

+               fname, av_err2str(ret));

+        return ret;

+    }

+

+    av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);

+

+    av_bprintf(&buf, "set xtics 0.1\n");

+    av_bprintf(&buf, "set ytics 0.1\n");

+    av_bprintf(&buf, "set size square\n");

+    av_bprintf(&buf, "set grid\n");

+

+    for (i = 0; i < FF_ARRAY_ELEMS(colors); i++) {

+        av_bprintf(&buf, "%s'-' using 1:2 with lines lc '%s' title ''",

+                   i ? ", " : "plot ", colors[i]);

+        if (comp_points[i])

+            av_bprintf(&buf, ", '-' using 1:2 with points pointtype 3 lc '%s' title ''",

+                    colors[i]);

+    }

+    av_bprintf(&buf, "\n");

+

+    for (i = 0; i < FF_ARRAY_ELEMS(colors); i++) {

+        int x;

+

+        /* plot generated values */

+        for (x = 0; x < 256; x++)

+            av_bprintf(&buf, "%f %f\n", x/255., graph[i][x]/255.);

+        av_bprintf(&buf, "e\n");

+

+        /* plot user knots */

+        if (comp_points[i]) {

+            const struct keypoint *point = comp_points[i];

+

+            while (point) {

+                av_bprintf(&buf, "%f %f\n", point->x, point->y);

+                point = point->next;

+            }

+            av_bprintf(&buf, "e\n");

+        }

+    }

+

+    fwrite(buf.str, 1, buf.len, f);

+    fclose(f);

+    av_bprint_finalize(&buf, NULL);

+    return 0;

+}

+

 static av_cold int init(AVFilterContext *ctx)

 {

     int i, j, ret;

@@ -448,6 +509,9 @@ static av_cold int init(AVFilterContext *ctx)

         }

     }

+    if (curves->plot_filename)

+        dump_curves(curves->plot_filename, curves->graph, comp_points);

+

     for (i = 0; i < NB_COMP + 1; i++) {

         struct keypoint *point = comp_points[i];

         while (point) {