Propagate palette gamut and ceiling between tonal and gamut tabs

Author: kipcole9

lib/color/palette/visualizer.ex

@@ -197,7 +197,9 @@ defmodule Color.Palette.Visualizer do
         gamuts: gamuts,
         planckian: truthy?(Map.get(params, "planckian")),
         overlay_seed: checkbox_default(params, "overlay_seed", true),
-        overlay_palette: checkbox_default(params, "overlay_palette", true)
+        overlay_palette: checkbox_default(params, "overlay_palette", true),
+        palette_gamut: gamut_atom(Map.get(params, "palette_gamut")) || :SRGB,
+        palette_chroma_ceiling: number_default(Map.get(params, "palette_chroma_ceiling"), 1.0)
       }
     end
 

lib/color/palette/visualizer/gamut_view.ex

@@ -13,17 +13,39 @@ defmodule Color.Palette.Visualizer.GamutView do
     {:ProPhoto, "ProPhoto RGB", "#f43f5e", false}
   ]
 
+  # Palette-gamut dropdown options — mirrors TonalView so the
+  # gamut view can reproduce the same tonal palette the Tonal tab
+  # would generate.
+  @palette_gamut_options [
+    {:SRGB, "sRGB"},
+    {:P3_D65, "P3 (D65)"},
+    {:Rec2020, "Rec2020"},
+    {:Adobe, "Adobe RGB"},
+    {:ProPhoto, "ProPhoto"}
+  ]
+
   def render(params, base) do
     projection = Map.get(params, :projection, :uv)
     enabled = Map.get(params, :gamuts, default_gamuts())
     show_planck = Map.get(params, :planckian, true)
     overlay_seed = Map.get(params, :overlay_seed, true)
     overlay_palette = Map.get(params, :overlay_palette, false)
+    palette_gamut = Map.get(params, :palette_gamut, :SRGB)
+    palette_chroma_ceiling = Map.get(params, :palette_chroma_ceiling, 1.0)
     seed = Map.get(params, :seed, "#3b82f6")
 
     body =
       try do
-        success_body(projection, enabled, show_planck, overlay_seed, overlay_palette, seed)
+        success_body(
+          projection,
+          enabled,
+          show_planck,
+          overlay_seed,
+          overlay_palette,
+          seed,
+          palette_gamut,
+          palette_chroma_ceiling
+        )
       rescue
         e ->
           ["<div class=\"vz-error\">", Render.escape(Exception.message(e)), "</div>"]
@@ -35,15 +57,38 @@ defmodule Color.Palette.Visualizer.GamutView do
       seed: seed,
       body: body,
       base: base,
-      extra_fields: extra_fields(projection, enabled, show_planck, overlay_seed, overlay_palette)
+      extra_fields:
+        extra_fields(
+          projection,
+          enabled,
+          show_planck,
+          overlay_seed,
+          overlay_palette,
+          palette_gamut,
+          palette_chroma_ceiling
+        ),
+      tab_params: %{
+        "tonal" => %{
+          "gamut" => Atom.to_string(palette_gamut),
+          "chroma_ceiling" => format_ceiling(palette_chroma_ceiling)
+        }
+      }
     )
   end
 
   defp default_gamuts do
     for {atom, _label, _colour, default?} <- @working_spaces, default?, do: atom
   end
 
-  defp extra_fields(projection, enabled, show_planck, overlay_seed, overlay_palette) do
+  defp extra_fields(
+         projection,
+         enabled,
+         show_planck,
+         overlay_seed,
+         overlay_palette,
+         palette_gamut,
+         palette_chroma_ceiling
+       ) do
     [
       "<label>proj <select name=\"projection\">",
       option("uv", "u′v′ (CIE 1976)", projection == :uv),
@@ -73,10 +118,24 @@ defmodule Color.Palette.Visualizer.GamutView do
       "<label><input type=\"checkbox\" name=\"overlay_palette\" value=\"1\"",
       if(overlay_palette, do: " checked", else: ""),
       "> Plot tonal palette</label>",
+      "<label>palette gamut <select name=\"palette_gamut\">",
+      Enum.map(@palette_gamut_options, fn {atom, label} ->
+        selected = if atom == palette_gamut, do: " selected", else: ""
+        ["<option value=\"", Atom.to_string(atom), "\"", selected, ">", label, "</option>"]
+      end),
+      "</select></label>",
+      "<label>palette ceiling <input type=\"number\" name=\"palette_chroma_ceiling\"",
+      " min=\"0.1\" max=\"1.0\" step=\"0.05\" value=\"",
+      format_ceiling(palette_chroma_ceiling),
+      "\"></label>",
       "<input type=\"hidden\" name=\"submitted\" value=\"1\">"
     ]
   end
 
+  defp format_ceiling(value) when is_float(value), do: :erlang.float_to_binary(value, decimals: 2)
+  defp format_ceiling(value) when is_integer(value), do: Integer.to_string(value)
+  defp format_ceiling(value), do: to_string(value)
+
   defp option(value, label, selected?) do
     [
       "<option value=\"",
@@ -89,8 +148,20 @@ defmodule Color.Palette.Visualizer.GamutView do
     ]
   end
 
-  defp success_body(projection, enabled, show_planck, overlay_seed, overlay_palette, seed) do
-    palette = if overlay_palette, do: safe_tonal(seed), else: nil
+  defp success_body(
+         projection,
+         enabled,
+         show_planck,
+         overlay_seed,
+         overlay_palette,
+         seed,
+         palette_gamut,
+         palette_chroma_ceiling
+       ) do
+    palette =
+      if overlay_palette,
+        do: safe_tonal(seed, palette_gamut, palette_chroma_ceiling),
+        else: nil
 
     svg_binary =
       Color.Gamut.SVG.render(
@@ -120,8 +191,8 @@ defmodule Color.Palette.Visualizer.GamutView do
     ]
   end
 
-  defp safe_tonal(seed) do
-    Color.Palette.Tonal.new(seed)
+  defp safe_tonal(seed, gamut, chroma_ceiling) do
+    Color.Palette.Tonal.new(seed, gamut: gamut, chroma_ceiling: chroma_ceiling)
   rescue
     _ -> nil
   end

lib/color/palette/visualizer/render.ex

@@ -30,6 +30,7 @@ defmodule Color.Palette.Visualizer.Render do
     error = Keyword.get(assigns, :error)
     base = Keyword.fetch!(assigns, :base)
     extra_fields = Keyword.get(assigns, :extra_fields, [])
+    tab_params = Keyword.get(assigns, :tab_params, %{})
 
     [
       "<!doctype html><html lang=\"en\"><head>",
@@ -42,7 +43,7 @@ defmodule Color.Palette.Visualizer.Render do
       escape(base),
       "/assets/style.css\">",
       "</head><body>",
-      header(active, seed, base, extra_fields),
+      header(active, seed, base, extra_fields, tab_params),
       "<main class=\"vz-main\">",
       error_block(error),
       body,
@@ -51,7 +52,7 @@ defmodule Color.Palette.Visualizer.Render do
     ]
   end
 
-  defp header(active, seed, base, extra_fields) do
+  defp header(active, seed, base, extra_fields, tab_params) do
     tabs = [
       {"tonal", "Tonal"},
       {"theme", "Theme"},
@@ -73,14 +74,15 @@ defmodule Color.Palette.Visualizer.Render do
       "<nav class=\"vz-tabs\">",
       Enum.map(tabs, fn {path, label} ->
         cls = if path == active, do: "active", else: ""
+        extras = Map.get(tab_params, path, %{})
+        query = tab_query_string(seed, extras)
 
         [
           "<a href=\"",
           escape(base),
           "/",
           path,
-          "?seed=",
-          URI.encode_www_form(seed),
+          query,
           "\" class=\"",
           cls,
           "\">",
@@ -109,6 +111,27 @@ defmodule Color.Palette.Visualizer.Render do
     ]
   end
 
+  # Builds the `?seed=…&k=v&…` query string appended to each tab's
+  # nav link. The seed is always included; callers can supply
+  # per-tab extras (e.g., palette_gamut) via the `tab_params` map
+  # on `Render.page/1`.
+  defp tab_query_string(seed, extras) when extras == %{} do
+    "?seed=" <> URI.encode_www_form(seed)
+  end
+
+  defp tab_query_string(seed, extras) do
+    base = "?seed=" <> URI.encode_www_form(seed)
+
+    extra_pairs =
+      extras
+      |> Enum.map(fn {k, v} ->
+        URI.encode_www_form(to_string(k)) <> "=" <> URI.encode_www_form(to_string(v))
+      end)
+      |> Enum.join("&")
+
+    base <> "&" <> extra_pairs
+  end
+
   @doc """
   Resolves any colour input to a 7-char hex string suitable for
   `<input type="color">`. Falls back to `default` if parsing

lib/color/palette/visualizer/tonal_view.ex

@@ -33,7 +33,13 @@ defmodule Color.Palette.Visualizer.TonalView do
       body: body,
       error: error,
       base: base,
-      extra_fields: extra_fields(hue_drift?, gamut, chroma_ceiling)
+      extra_fields: extra_fields(hue_drift?, gamut, chroma_ceiling),
+      tab_params: %{
+        "gamut" => %{
+          "palette_gamut" => Atom.to_string(gamut),
+          "palette_chroma_ceiling" => format_ceiling(chroma_ceiling)
+        }
+      }
     )
   end