Add palette gradient based on Hue (fix #2171)

src/app/ui/color_bar.cpp

@@ -57,6 +57,7 @@
 #include "doc/image.h"
 #include "doc/image_impl.h"
 #include "doc/palette.h"
+#include "doc/palette_gradient_type.h"
 #include "doc/primitives.h"
 #include "doc/remap.h"
 #include "doc/rgbmap.h"
@@ -924,16 +925,21 @@ void ColorBar::onSortBy(SortPaletteBy channel)
   setPalette(&newPalette, "Sort Colors");
 }
 
-void ColorBar::onGradient()
+void ColorBar::onGradient(GradientType gradientType)
 {
   int index1, index2;
   if (!m_paletteView.getSelectedRange(index1, index2))
     return;
 
   Palette newPalette(*get_current_palette());
-  newPalette.makeGradient(index1, index2);
-
-  setPalette(&newPalette, "Gradient");
+  if (gradientType == GradientType::LINEAR) {
+    newPalette.makeGradient(index1, index2);
+    setPalette(&newPalette, "Gradient");
+  }
+  else {
+    newPalette.makeHueGradient(index1, index2);
+    setPalette(&newPalette, "Gradient by Hue");
+  }
 }
 
 void ColorBar::setAscending(bool ascending)
@@ -1249,6 +1255,7 @@ void ColorBar::showPaletteSortOptions()
   MenuItem
     rev("Reverse Colors"),
     grd("Gradient"),
+    grh("Gradient by Hue"),
     hue("Sort by Hue"),
     sat("Sort by Saturation"),
     bri("Sort by Brightness"),
@@ -1261,6 +1268,7 @@ void ColorBar::showPaletteSortOptions()
     des("Descending");
   menu.addChild(&rev);
   menu.addChild(&grd);
+  menu.addChild(&grh);
   menu.addChild(new ui::MenuSeparator);
   menu.addChild(&hue);
   menu.addChild(&sat);
@@ -1279,7 +1287,8 @@ void ColorBar::showPaletteSortOptions()
   else des.setSelected(true);
 
   rev.Click.connect([this]{ onReverseColors(); });
-  grd.Click.connect([this]{ onGradient(); });
+  grd.Click.connect([this]{ onGradient(GradientType::LINEAR); });
+  grh.Click.connect([this]{ onGradient(GradientType::HUE); });
   hue.Click.connect([this]{ onSortBy(SortPaletteBy::HUE); });
   sat.Click.connect([this]{ onSortBy(SortPaletteBy::SATURATION); });
   bri.Click.connect([this]{ onSortBy(SortPaletteBy::VALUE); });

src/app/ui/color_bar.h

@@ -17,6 +17,7 @@
 #include "app/ui/color_button.h"
 #include "app/ui/input_chain_element.h"
 #include "app/ui/palette_view.h"
+#include "doc/palette_gradient_type.h"
 #include "doc/pixel_format.h"
 #include "doc/sort_palette.h"
 #include "obs/connection.h"
@@ -119,7 +120,7 @@ namespace app {
     void onPickSpectrum(const app::Color& color, ui::MouseButton button);
     void onReverseColors();
     void onSortBy(doc::SortPaletteBy channel);
-    void onGradient();
+    void onGradient(GradientType gradientType);
     void onFixWarningClick(ColorButton* colorButton, ui::Button* warningIcon);
     void onTimerTick();
     void setAscending(bool ascending);

src/doc/palette.cpp

@@ -13,7 +13,10 @@
 
 #include "base/base.h"
 #include "doc/image.h"
+#include "doc/palette_gradient_type.h"
 #include "doc/remap.h"
+#include "gfx/hsv.h"
+#include "gfx/rgb.h"
 
 #include <algorithm>
 #include <limits>
@@ -206,6 +209,64 @@ void Palette::makeGradient(int from, int to)
   }
 }
 
+void Palette::makeHueGradient(int from, int to)
+{
+  int r1, g1, b1, a1;
+  int r2, g2, b2, a2;
+  int i, n;
+
+  ASSERT(from >= 0 && from < size());
+  ASSERT(to >= 0 && to < size());
+
+  if (from > to)
+    std::swap(from, to);
+
+  n = to - from;
+  if (n < 2)
+    return;
+
+  r1 = rgba_getr(getEntry(from));
+  g1 = rgba_getg(getEntry(from));
+  b1 = rgba_getb(getEntry(from));
+  a1 = rgba_geta(getEntry(from));
+
+  r2 = rgba_getr(getEntry(to));
+  g2 = rgba_getg(getEntry(to));
+  b2 = rgba_getb(getEntry(to));
+  a2 = rgba_geta(getEntry(to));
+
+  gfx::Hsv hsv1(gfx::Rgb(r1, g1, b1));
+  gfx::Hsv hsv2(gfx::Rgb(r2, g2, b2));
+
+  double h1 = hsv1.hue();
+  double s1 = hsv1.saturation();
+  double v1 = hsv1.value();
+
+  double h2 = hsv2.hue();
+  double s2 = hsv2.saturation();
+  double v2 = hsv2.value();
+
+  if (h2 >= h1) {
+    if (h2-h1 > 180.0)
+      h2 = h2 - 360.0;
+  }
+  else {
+    if (h1-h2 > 180.0)
+      h2 = h2 + 360.0;
+  }
+
+  gfx::Hsv hsv;
+  for (i=from+1; i<to; ++i) {
+    double t = double(i - from) / double(n);
+    hsv.hue(h1 + (h2 - h1) * t);
+    hsv.saturation(s1 + (s2 - s1) * t);
+    hsv.value(v1 + (v2 - v1) * t);
+    int alpha = int(a1 + double(a2 - a1) * t);
+    gfx::Rgb rgb(hsv);
+    setEntry(i, rgba(rgb.red(), rgb.green(), rgb.blue(), alpha));
+  }
+}
+
 int Palette::findExactMatch(int r, int g, int b, int a, int mask_index) const
 {
   for (int i=0; i<(int)m_colors.size(); ++i)

src/doc/palette.h

@@ -13,6 +13,7 @@
 #include "doc/color.h"
 #include "doc/frame.h"
 #include "doc/object.h"
+#include "doc/palette_gradient_type.h"
 
 #include <vector>
 #include <string>
@@ -90,6 +91,7 @@ namespace doc {
     void makeBlack();
 
     void makeGradient(int from, int to);
+    void makeHueGradient(int from, int to);
 
     int findExactMatch(int r, int g, int b, int a, int mask_index) const;
     int findBestfit(int r, int g, int b, int a, int mask_index) const;

src/doc/palette_gradient_type.h

@@ -0,0 +1,20 @@
+// Aseprite Document Library
+// Copyright (c) 2020 Igara Studio S.A.
+//
+// This file is released under the terms of the MIT license.
+// Read LICENSE.txt for more information.
+
+#ifndef DOC_PALETTE_GRADIENT_TYPE_H_INCLUDED
+#define DOC_PALETTE_GRADIENT_TYPE_H_INCLUDED
+#pragma once
+
+namespace doc {
+
+  enum class GradientType {
+    LINEAR,
+    HUE,
+  };
+
+} // namespace doc
+
+#endif