scope: add option for luma display in waveform & histogram

data/darktableconfig.xml.in

@@ -3362,6 +3362,13 @@
     <shortdescription/>
     <longdescription/>
   </dtconfig>
+  <dtconfig>
+    <name>plugins/darkroom/histogram/show_luma</name>
+    <type>bool</type>
+    <default>false</default>
+    <shortdescription/>
+    <longdescription/>
+  </dtconfig>
   <dtconfig>
     <name>plugins/darkroom/histogram/vectorscope/harmony_type</name>
     <type>

data/themes/darktable.css

@@ -224,6 +224,7 @@ Why that? Just because it's a developer choice and most classes use underscore i
 @define-color graph_red rgb(237,30,20);
 @define-color graph_green rgb(28,235,26);
 @define-color graph_blue rgb(14,14,233);
+@define-color graph_white @grey_95;
 
 @define-color colorlabel_red rgb(230,0,0);
 @define-color colorlabel_green rgb(0,230,0);
@@ -745,6 +746,11 @@ dialog .sidebar row:selected:hover label,
   background-color: alpha(@graph_blue, 0.2);
 }
 
+#luma-toggle-button
+{
+  background-color: alpha(white, 0.2);
+}
+
 /* set now them active state */
 #red-channel-button:checked
 {
@@ -761,6 +767,11 @@ dialog .sidebar row:selected:hover label,
   background-color: alpha(@graph_blue, 0.66);
 }
 
+#luma-toggle-button:checked
+{
+  background-color: alpha(white, 0.66);
+}
+
 /* set now hover state */
 #red-channel-button:hover
 {
@@ -777,6 +788,27 @@ dialog .sidebar row:selected:hover label,
   background-color: alpha(@graph_blue, 0.5);
 }
 
+#luma-toggle-button:hover
+{
+  background-color: alpha(white, 0.5);
+}
+
+/* inactive state */
+#red-channel-button:disabled
+{
+  background-color: alpha(@graph_red, 0.1);
+}
+
+#green-channel-button:disabled
+{
+  background-color: alpha(@graph_green, 0.1);
+}
+
+#blue-channel-button:disabled
+{
+  background-color: alpha(@graph_blue, 0.1);
+}
+
 /*------------------
   - Dialog windows -
   ------------------*/

src/bauhaus/bauhaus.c

@@ -811,6 +811,8 @@ void dt_bauhaus_load_theme()
                                  &bh->graph_colors[1]);
   gtk_style_context_lookup_color(ctx, "graph_blue",
                                  &bh->graph_colors[2]);
+  gtk_style_context_lookup_color(ctx, "graph_white",
+                                 &bh->graph_colors[3]);
   gtk_style_context_lookup_color(ctx, "colorlabel_red",
                                  &bh->colorlabels[DT_COLORLABELS_RED]);
   gtk_style_context_lookup_color(ctx, "colorlabel_yellow",

src/bauhaus/bauhaus.h

@@ -152,7 +152,7 @@ typedef struct dt_bauhaus_t
 
   // colors for graphs
   GdkRGBA graph_bg, graph_exterior, graph_border, graph_fg, graph_grid, graph_fg_active, graph_overlay, inset_histogram;
-  GdkRGBA graph_colors[3];               // primaries
+  GdkRGBA graph_colors[4];               // additive primaries and luma white
   GdkRGBA colorlabels[DT_COLORLABELS_LAST];
 } dt_bauhaus_t;
 

src/common/histogram.c

@@ -1,6 +1,6 @@
 /*
     This file is part of darktable,
-    Copyright (C) 2014-2023 darktable developers.
+    Copyright (C) 2014-2026 darktable developers.
 
     darktable is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -70,6 +70,28 @@ static inline void _bin_raw(const dt_dev_histogram_collection_params_t *const pa
 
 //------------------------------------------------------------------------------
 
+static inline void _bin_luma(const dt_dev_histogram_collection_params_t *const params,
+                             const void *const restrict pixel,
+                             uint32_t *const restrict histogram,
+                             const int j,
+                             const dt_iop_order_iccprofile_info_t *const profile)
+{
+  const dt_histogram_roi_t *roi = params->roi;
+  float *in = (float *)pixel + 4 * (roi->width * j + roi->crop_x);
+  const float max_bin = params->bins_count - 1;
+
+  for(int i = 0; i < roi->width - roi->crop_right - roi->crop_x; i++)
+  {
+    const float luma = profile->matrix_in[1][0] * in[i*4]
+                       + profile->matrix_in[1][1] * in[i*4+1]
+                       + profile->matrix_in[1][2] * in[i*4+2];
+    const size_t bin = CLAMP(max_bin * luma, 0.0f, max_bin);
+    histogram[bin]++;
+  }
+}
+
+//------------------------------------------------------------------------------
+
 static inline void _bin_rgb(const dt_dev_histogram_collection_params_t *const params,
                             const void *const restrict pixel,
                             uint32_t *const restrict histogram,
@@ -225,15 +247,23 @@ void dt_histogram_helper(dt_dev_histogram_collection_params_t *histogram_params,
       break;
 
     case IOP_CS_RGB:
-      histogram_stats->ch = 3u;
-      if(compensate_middle_grey && profile_info)
-        // for rgbcurve (compensated)
+      if(histogram_stats->ch == 1u)
+        // for histogram utility module
         _hist_worker(histogram_params, histogram_stats, pixel, histogram,
-                     _bin_rgb_compensated, profile_info);
+                     _bin_luma, profile_info);
       else
-        // used by levels, rgbcurve (uncompensated), rgblevels
-        _hist_worker(histogram_params, histogram_stats, pixel, histogram,
-                     _bin_rgb, profile_info);
+      {
+        histogram_stats->ch = 3u;
+        if(compensate_middle_grey && profile_info)
+          // for rgbcurve (compensated)
+          _hist_worker(histogram_params, histogram_stats, pixel, histogram,
+                       _bin_rgb_compensated, profile_info);
+        else
+          // used by levels, rgbcurve (uncompensated), rgblevels, and
+          // histogram utility module
+          _hist_worker(histogram_params, histogram_stats, pixel, histogram,
+                       _bin_rgb, profile_info);
+      }
       break;
 
     case IOP_CS_LAB:
@@ -257,7 +287,7 @@ void dt_histogram_helper(dt_dev_histogram_collection_params_t *histogram_params,
   if(*histogram && histogram_max)
   {
     // RGB, Lab, and LCh
-    if(cst == IOP_CS_RGB || IOP_CS_LAB)
+    if(cst == IOP_CS_RGB || cst == IOP_CS_LAB)
     {
       uint32_t *hist = *histogram;
 
@@ -271,9 +301,15 @@ void dt_histogram_helper(dt_dev_histogram_collection_params_t *histogram_params,
         m[2] = hist[2];
       }
 
-      for(int k = 4; k < 4 * histogram_stats->bins_count; k += 4)
-        for_each_channel(ch,aligned(hist:64) aligned(m:16))
-          m[ch] = MAX(m[ch], hist[k+ch]);
+      // intentionally skip first bucket to show bit more y-axis range
+      // for underexposed images
+      if(histogram_stats->ch == 1u)
+        for(int k = 1; k < histogram_stats->bins_count; k++)
+          m[0] = MAX(m[0], hist[k]);
+      else
+        for(int k = 4; k < 4 * histogram_stats->bins_count; k += 4)
+          for_each_channel(ch,aligned(hist:64) aligned(m:16))
+            m[ch] = MAX(m[ch], hist[k+ch]);
     }
     else
       // raw max not implemented, as is only seen in exposure

src/develop/pixelpipe.h

@@ -110,7 +110,7 @@ typedef struct dt_dev_histogram_stats_t
   size_t buf_size;
   /** count of pixels sampled during histogram capture. */
   uint32_t pixels;
-  /** count of channels: 1 for RAW, 3 for rgb/Lab. */
+  /** count of channels: 1 for RAW/luma, 3 for rgb/Lab. */
   uint32_t ch;
 } dt_dev_histogram_stats_t;
 

src/libs/histogram.c

@@ -41,10 +41,10 @@ static void _lib_histogram_get_sector_angles(dt_lib_module_t *self,
                                              float *angles,
                                              int *n);
 
-static const gchar *rgb_names[DT_SCOPES_RGB_N] =
+static const gchar *channel_names[DT_SCOPES_CH_N] =
   { N_("red"),
     N_("green"),
-    N_("blue")
+    N_("blue"),
   };
 
 const char *name(dt_lib_module_t *self)
@@ -442,7 +442,7 @@ static void _mode_toggle(GtkWidget *button, dt_scopes_t *s)
   lib_histogram_update_tooltip(s);
 
   dt_scopes_call(prior_mode, mode_leave);
-  gtk_widget_set_visible(s->button_box_rgb,
+  gtk_widget_set_visible(s->button_box_channels,
                          dt_scopes_func_exists(s->cur_mode, draw_scope_channels));
   dt_scopes_call(s->cur_mode, update_buttons);
   dt_scopes_call(s->cur_mode, mode_enter);
@@ -457,12 +457,12 @@ static void _mode_toggle(GtkWidget *button, dt_scopes_t *s)
 
 static void _channel_toggle(GtkWidget *button, dt_scopes_t *s)
 {
-  for(int i = 0; i < DT_SCOPES_RGB_N; i++)
-    if(s->channel_buttons[i] == button)
+  for(int i = 0; i < DT_SCOPES_CH_N; i++)
+    if(s->channel_btns[i] == button)
     {
       char conf[48];
       g_snprintf(conf, sizeof(conf),
-                 "plugins/darkroom/histogram/show_%s", rgb_names[i]);
+                 "plugins/darkroom/histogram/show_%s", channel_names[i]);
       s->channels[i]
         = gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(button));
       dt_conf_set_bool(conf, s->channels[i]);
@@ -537,7 +537,7 @@ static void _eventbox_enter_notify_callback(GtkEventControllerMotion *controller
     if(s->cur_mode != &s->modes[i])
       dt_scopes_call(&s->modes[i], mode_leave);
   dt_scopes_call(s->cur_mode, mode_enter);
-  gtk_widget_set_visible(s->button_box_rgb,
+  gtk_widget_set_visible(s->button_box_channels,
                          dt_scopes_func_exists(s->cur_mode, draw_scope_channels));
   gtk_widget_show(s->button_box_left);
   gtk_widget_show(s->button_box_right);
@@ -675,11 +675,11 @@ void gui_init(dt_lib_module_t *self)
 
   dt_pthread_mutex_init(&s->lock, NULL);
 
-  s->channels[DT_SCOPES_RGB_RED]
+  s->channels[DT_SCOPES_CH_RED]
     = dt_conf_get_bool("plugins/darkroom/histogram/show_red");
-  s->channels[DT_SCOPES_RGB_GREEN]
+  s->channels[DT_SCOPES_CH_GREEN]
     = dt_conf_get_bool("plugins/darkroom/histogram/show_green");
-  s->channels[DT_SCOPES_RGB_BLUE]
+  s->channels[DT_SCOPES_CH_BLUE]
     = dt_conf_get_bool("plugins/darkroom/histogram/show_blue");
 
   // proxy functions and data so that pixelpipe or tether can
@@ -804,28 +804,31 @@ void gui_init(dt_lib_module_t *self)
                        GDK_KEY_H, GDK_CONTROL_MASK | GDK_SHIFT_MASK);
 
   // RGB channel buttons
-  s->button_box_rgb = dt_gui_hbox();
-  gtk_widget_set_valign(s->button_box_rgb, GTK_ALIGN_CENTER);
-  gtk_widget_set_halign(s->button_box_rgb, GTK_ALIGN_CENTER);
-  // red/green/blue channel on/off
-  for(int i=DT_SCOPES_RGB_RED; i < DT_SCOPES_RGB_N; i++)
+  s->button_box_channels = dt_gui_hbox();
+  gtk_widget_set_valign(s->button_box_channels, GTK_ALIGN_CENTER);
+  gtk_widget_set_halign(s->button_box_channels, GTK_ALIGN_CENTER);
+  // red/green/blue on/off
+  for(int i=DT_SCOPES_CH_RED; i < DT_SCOPES_CH_N; i++)
   {
-    g_autofree char *name = g_strdup_printf("%s-channel-button", rgb_names[i]);
-    g_autofree char *tip = g_strdup_printf(_("toggle %s channel"), _(rgb_names[i]));
+    g_autofree char *name = g_strdup_printf("%s-channel-button", channel_names[i]);
+    g_autofree char *tip = g_strdup_printf(_("toggle %s channel"), _(channel_names[i]));
     GtkWidget *btn = dtgtk_togglebutton_new(dtgtk_cairo_paint_color,
                                             CPF_NONE, NULL);
     dt_gui_add_class(btn, "rgb_toggle");
     gtk_widget_set_name(btn, name);
     gtk_widget_set_tooltip_text(btn, tip);
     gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(btn),
                                  s->channels[i]);
-    dt_action_define(dark, N_("toggle colors"), rgb_names[i], btn, &dt_action_def_toggle);
-    dt_gui_box_add(s->button_box_rgb, btn);
+    dt_action_define(dark, N_("toggle colors"), channel_names[i], btn, &dt_action_def_toggle);
     g_signal_connect(G_OBJECT(btn), "toggled", G_CALLBACK(_channel_toggle), s);
-    s->channel_buttons[i] = btn;
+    s->channel_btns[i] = btn;
   }
-  // RGB channels are always rightmost
-  dt_gui_box_add(s->button_box_right, s->button_box_rgb);
+  dt_gui_box_add(s->button_box_channels,
+                 s->channel_btns[DT_SCOPES_CH_RED],
+                 s->channel_btns[DT_SCOPES_CH_GREEN],
+                 s->channel_btns[DT_SCOPES_CH_BLUE]);
+  // channels are always rightmost
+  dt_gui_box_add(s->button_box_right, s->button_box_channels);
 
   for(dt_scopes_mode_type_t i = 0; i < DT_SCOPES_MODE_N; i++)
   {

src/libs/scopes.h

@@ -43,15 +43,15 @@ typedef enum dt_scopes_highlight_t
   DT_SCOPES_HIGHLIGHT_EXPOSURE
 } dt_scopes_highlight_t;
 
-typedef enum dt_scopes_rgb_t
+typedef enum dt_scopes_channels_t
 {
-  DT_SCOPES_RGB_RED = 0,
-  DT_SCOPES_RGB_GREEN,
-  DT_SCOPES_RGB_BLUE,
-  DT_SCOPES_RGB_N // needs to be the last one
-} dt_scopes_rgb_t;
+  DT_SCOPES_CH_RED = 0,
+  DT_SCOPES_CH_GREEN,
+  DT_SCOPES_CH_BLUE,
+  DT_SCOPES_CH_N // needs to be the last one
+} dt_scopes_channels_t;
 
-typedef gboolean scopes_channels_t[DT_SCOPES_RGB_N];
+typedef gboolean dt_scopes_channels_list_t[DT_SCOPES_CH_N];
 
 struct dt_scopes_t;
 struct dt_scopes_mode_t;
@@ -66,7 +66,7 @@ typedef struct dt_scopes_functions_t
                   const float *const input,
                   // FIXME: should ROI by dt_histogram_roi_t or another type?
                   dt_histogram_roi_t *const roi,
-                  const dt_iop_order_iccprofile_info_t *vs_prof);
+                  const dt_iop_order_iccprofile_info_t *profile);
   // FIXME: do want a proper clear function or just tag as not up to date?
   void (*clear)(struct dt_scopes_mode_t *const self);
   void (*draw_bkgd)(const struct dt_scopes_mode_t *const self,
@@ -90,7 +90,7 @@ typedef struct dt_scopes_functions_t
                               cairo_t *cr,
                               const int width,
                               const int height,
-                              const scopes_channels_t channels);
+                              const dt_scopes_channels_list_t channels);
   // FIXME: rename to something more sensible
   dt_scopes_highlight_t (*get_highlight)(const struct dt_scopes_mode_t *const self,
                                          const double posx,
@@ -140,16 +140,16 @@ typedef struct dt_scopes_t
   dt_scopes_mode_t modes[DT_SCOPES_MODE_N];     // all available modes
   int update_counter;                           // most recent pixelpipe vs mode data
   dt_scopes_highlight_t highlight;              // depends on mouse position
-  scopes_channels_t channels;                   // display state chosen by RGB buttons
+  dt_scopes_channels_list_t channels;           // RGB channels to display
   gboolean dragging;                            // to block motion handling during drag
   gdouble last_offset_x, last_offset_y;         // for drag handling
   // UI elements
   GtkWidget *overlay;                           // GtkOverlay -- scope and buttons
   GtkWidget *button_box_left;                   // GtkBox -- scope mode buttons
   GtkWidget *button_box_split;                  // GtkBox -- option buttons for left scope
   GtkWidget *button_box_right;                  // GtkBox -- option buttons for main scope
-  GtkWidget *button_box_rgb;                    // GtkBox -- RGB channels buttons
-  GtkWidget *channel_buttons[DT_SCOPES_RGB_N];  // Array of GtkToggleButton -- RGB channels
+  GtkWidget *button_box_channels;               // GtkBox -- RGB channel buttons
+  GtkWidget *channel_btns[DT_SCOPES_CH_N];      // Array of GtkToggleButton -- channels
   GtkWidget *scope_draw;                        // GtkDrawingArea -- scope & resize
   // for access to data during process/draw
   dt_pthread_mutex_t lock;