vf_curves: add option to set all curves at once

Reviewed-by: ubitux
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/filters.texi

@@ -2385,6 +2385,11 @@ Set the key points for the red component.
 Set the key points for the green component.
 @item blue, b
 Set the key points for the blue component.
+@item all
+Set the key points for all components.
+Can be used in addition to the other key points component
+options. In this case, the unset component(s) will fallback on this
+@option{all} setting.
 @item preset
 Select one of the available color presets. This option can not be used in
 addition to the @option{r}, @option{g}, @option{b} parameters.

libavfilter/vf_curves.c

@@ -52,6 +52,7 @@ typedef struct {
     const AVClass *class;
     enum preset preset;
     char *comp_points_str[NB_COMP];
+    char *comp_points_str_all;
     uint8_t graph[NB_COMP][256];
 } CurvesContext;
 
@@ -64,6 +65,7 @@ static const AVOption curves_options[] = {
     { "g",     "set green points coordinates", OFFSET(comp_points_str[1]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
     { "blue",  "set blue points coordinates",  OFFSET(comp_points_str[2]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
     { "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 },
     { "preset", "select a color curves preset", OFFSET(preset), AV_OPT_TYPE_INT, {.i64=PRESET_NONE}, PRESET_NONE, NB_PRESETS-1, FLAGS, "preset_name" },
         { "color_negative",     NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_COLOR_NEGATIVE},       INT_MIN, INT_MAX, FLAGS, "preset_name" },
         { "cross_process",      NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_CROSS_PROCESS},        INT_MIN, INT_MAX, FLAGS, "preset_name" },
@@ -318,9 +320,18 @@ static av_cold int init(AVFilterContext *ctx, const char *args)
     int i, j, ret;
     CurvesContext *curves = ctx->priv;
     struct keypoint *comp_points[NB_COMP] = {0};
+    char **pts = curves->comp_points_str;
+
+    if (curves->comp_points_str_all) {
+        for (i = 0; i < NB_COMP; i++) {
+            if (!pts[i])
+                pts[i] = av_strdup(curves->comp_points_str_all);
+            if (!pts[i])
+                return AVERROR(ENOMEM);
+        }
+    }
 
     if (curves->preset != PRESET_NONE) {
-        char **pts = curves->comp_points_str;
         if (pts[0] || pts[1] || pts[2]) {
             av_log(ctx, AV_LOG_ERROR, "It is not possible to mix a preset "
                    "with explicit points placements\n");