From 78aff4dde680d24c2a2aa62df2d73aacb20bf62f Mon Sep 17 00:00:00 2001
From: Ell <ell_se@yahoo.com>
Date: Sun, 22 Oct 2017 14:30:34 -0400
Subject: [PATCH] app: add compress-threshold-range prop to color-to-alpha-plus
 gui

When set, the opacity and transparenct threshold range is compressed
to the minimal extent that would produce different results.

When the property is toggled, update the opacity and transparency
thresholds, such that the result remains the same.
---
 app/propgui/gimppropgui-color-to-alpha.c | 101 +++++++++++++++++++----
 1 file changed, 86 insertions(+), 15 deletions(-)

diff --git a/app/propgui/gimppropgui-color-to-alpha.c b/app/propgui/gimppropgui-color-to-alpha.c
index af4729787b..ae022d3ed3 100644
--- a/app/propgui/gimppropgui-color-to-alpha.c
+++ b/app/propgui/gimppropgui-color-to-alpha.c
@@ -37,38 +37,99 @@
 #include "gimp-intl.h"
 
 
+static gdouble
+get_max_color_extent (GObject *config)
+{
+  GimpRGB *color;
+  gdouble  max_extent = 0.0;
+
+  g_object_get (config,
+                "color", &color,
+                NULL);
+
+  max_extent = MAX (max_extent, MAX (color->r, 1.0 - color->r));
+  max_extent = MAX (max_extent, MAX (color->g, 1.0 - color->g));
+  max_extent = MAX (max_extent, MAX (color->b, 1.0 - color->b));
+
+  g_free (color);
+
+  return max_extent;
+}
+
+static gdouble
+compress_threshold (GObject *config,
+                    gdouble  threshold)
+{
+  return MIN (threshold / get_max_color_extent (config), 1.0);
+}
+
+static gdouble
+uncompress_threshold (GObject *config,
+                      gdouble  threshold)
+{
+  return threshold * get_max_color_extent (config);
+}
+
 static void
 threshold_picked (GObject       *config,
                   gpointer       identifier,
                   gdouble        x,
                   gdouble        y,
                   const Babl    *sample_format,
-                  const GimpRGB *color)
+                  const GimpRGB *picked_color)
 {
-  GimpRGB *bg_color;
-  gdouble  radius        = 0.0;
-  gdouble  target_radius = 0.0;
-  gdouble  threshold;
+  GimpRGB  *color;
+  gboolean  compress_threshold_range;
+  gdouble   threshold = 0.0;
 
   g_object_get (config,
-                "color", &bg_color,
+                "color",                    &color,
+                "compress-threshold-range", &compress_threshold_range,
                 NULL);
 
-  radius = MAX (radius, MAX (bg_color->r, 1.0 - bg_color->r));
-  radius = MAX (radius, MAX (bg_color->g, 1.0 - bg_color->g));
-  radius = MAX (radius, MAX (bg_color->b, 1.0 - bg_color->b));
+  threshold = MAX (threshold, fabs (picked_color->r - color->r));
+  threshold = MAX (threshold, fabs (picked_color->g - color->g));
+  threshold = MAX (threshold, fabs (picked_color->b - color->b));
 
-  target_radius = MAX (target_radius, fabs (color->r - bg_color->r));
-  target_radius = MAX (target_radius, fabs (color->g - bg_color->g));
-  target_radius = MAX (target_radius, fabs (color->b - bg_color->b));
-
-  threshold = target_radius / radius;
+  if (compress_threshold_range)
+    threshold = compress_threshold (config, threshold);
 
   g_object_set (config,
                 identifier, threshold,
                 NULL);
 
-  g_free (bg_color);
+  g_free (color);
+}
+
+static void
+compress_threshold_range_clicked (GtkWidget *toggle,
+                                  GObject   *config)
+{
+  gdouble  transparency_threshold;
+  gdouble  opacity_threshold;
+  gboolean compress_threshold_range;
+
+  g_object_get (config,
+                "transparency-threshold",   &transparency_threshold,
+                "opacity-threshold",        &opacity_threshold,
+                "compress-threshold-range", &compress_threshold_range,
+                NULL);
+
+  if (compress_threshold_range)
+    {
+      transparency_threshold = compress_threshold (config, transparency_threshold);
+      opacity_threshold      = compress_threshold (config, opacity_threshold);
+    }
+  else
+    {
+      transparency_threshold = uncompress_threshold (config, transparency_threshold);
+      opacity_threshold      = uncompress_threshold (config, opacity_threshold);
+    }
+
+  g_object_set (config,
+                "transparency-threshold", transparency_threshold,
+                "opacity-threshold",      opacity_threshold,
+                NULL);
 }
 
 GtkWidget *
@@ -85,6 +146,7 @@ _gimp_prop_gui_new_color_to_alpha (GObject                  *config,
   GtkWidget   *button;
   GtkWidget   *hbox;
   GtkWidget   *scale;
+  GtkWidget   *toggle;
   const gchar *label;
 
   g_return_val_if_fail (G_IS_OBJECT (config), NULL);
@@ -144,5 +206,14 @@ _gimp_prop_gui_new_color_to_alpha (GObject                  *config,
       gtk_widget_show (button);
     }
 
+  toggle = gimp_prop_widget_new (config, "compress-threshold-range",
+                                 area, context, NULL, NULL, NULL, &label);
+  gtk_box_pack_start (GTK_BOX (vbox), toggle, FALSE, FALSE, 0);
+  gtk_widget_show (toggle);
+
+  g_signal_connect (toggle, "clicked",
+                    G_CALLBACK (compress_threshold_range_clicked),
+                    config);
+
   return vbox;
 }