avfilter/avf_showspectrum: add nebulae color map

Signed-off-by: Paul B Mahol <onemda@gmail.com>

doc/filters.texi

@@ -14619,6 +14619,8 @@ each channel is displayed using the same color scheme
 each channel is displayed using the rainbow color scheme
 @item moreland
 each channel is displayed using the moreland color scheme
+@item nebulae
+each channel is displayed using the nebulae color scheme
 @end table
 
 Default value is @samp{channel}.

libavfilter/avf_showspectrum.c

@@ -37,7 +37,7 @@
 
 enum DisplayMode  { COMBINED, SEPARATE, NB_MODES };
 enum DisplayScale { LINEAR, SQRT, CBRT, LOG, NB_SCALES };
-enum ColorMode    { CHANNEL, INTENSITY, RAINBOW, MORELAND, NB_CLMODES };
+enum ColorMode    { CHANNEL, INTENSITY, RAINBOW, MORELAND, NEBULAE, NB_CLMODES };
 enum SlideMode    { REPLACE, SCROLL, FULLFRAME, RSCROLL, NB_SLIDES };
 enum Orientation  { VERTICAL, HORIZONTAL, NB_ORIENTATIONS };
 
@@ -84,6 +84,7 @@ static const AVOption showspectrum_options[] = {
         { "intensity", "intensity based coloring",        0, AV_OPT_TYPE_CONST, {.i64=INTENSITY}, 0, 0, FLAGS, "color" },
         { "rainbow",   "rainbow based coloring",          0, AV_OPT_TYPE_CONST, {.i64=RAINBOW},   0, 0, FLAGS, "color" },
         { "moreland",  "moreland based coloring",         0, AV_OPT_TYPE_CONST, {.i64=MORELAND},  0, 0, FLAGS, "color" },
+        { "nebulae",   "nebulae based coloring",          0, AV_OPT_TYPE_CONST, {.i64=NEBULAE},   0, 0, FLAGS, "color" },
     { "scale", "set display scale", OFFSET(scale), AV_OPT_TYPE_INT, {.i64=SQRT}, LINEAR, NB_SCALES-1, FLAGS, "scale" },
         { "sqrt", "square root", 0, AV_OPT_TYPE_CONST, {.i64=SQRT},   0, 0, FLAGS, "scale" },
         { "cbrt", "cubic root",  0, AV_OPT_TYPE_CONST, {.i64=CBRT},   0, 0, FLAGS, "scale" },
@@ -144,6 +145,15 @@ static const struct ColorTable {
     { 0.73,           177/256.,     (103-128)/256.,      (165-128)/256. },
     { 0.86,           136/256.,     (100-128)/256.,      (183-128)/256. },
     {    1,            68/256.,     (117-128)/256.,      (203-128)/256. }},
+    [NEBULAE] = {
+    {    0,            10/256.,     (134-128)/256.,      (132-128)/256. },
+    { 0.23,            21/256.,     (137-128)/256.,      (130-128)/256. },
+    { 0.45,            35/256.,     (134-128)/256.,      (134-128)/256. },
+    { 0.57,            51/256.,     (130-128)/256.,      (139-128)/256. },
+    { 0.67,           104/256.,     (116-128)/256.,      (162-128)/256. },
+    { 0.77,           120/256.,     (105-128)/256.,      (188-128)/256. },
+    { 0.87,           140/256.,     (105-128)/256.,      (188-128)/256. },
+    {    1,                  1,                  0,                   0 }},
 };
 
 static av_cold void uninit(AVFilterContext *ctx)
@@ -392,6 +402,7 @@ static int plot_spectrum_column(AVFilterLink *inlink, AVFrame *insamples)
             switch (s->color_mode) {
             case RAINBOW:
             case MORELAND:
+            case NEBULAE:
             case INTENSITY:
                 uf = yf;
                 vf = yf;