Merge bd2ae1eb61 into 2ba051b59b

Although the issue refers to deselecting MovingPixelsState, the same
crash could happen when canceling/finishing WritingTextState or
MovingSelectionState. This fixes the crash for all these states.

data/pref.xml

@@ -329,6 +329,7 @@
     <section id="quantization">
       <option id="with_alpha" type="bool" default="true" />
       <option id="dithering_algorithm" type="std::string" />
+      <option id="zig_zag" type="bool" default="true" />
       <option id="dithering_factor" type="int" default="100" />
       <option id="to_gray" type="ToGrayAlgorithm" default="ToGrayAlgorithm::DEFAULT" />
       <option id="advanced" type="bool" default="false" />

data/strings/en.ini

@@ -235,8 +235,14 @@ ChangePixelFormat_Grayscale = Grayscale
 ChangePixelFormat_Indexed = Indexed
 ChangePixelFormat_Indexed_OrderedDithering = Indexed with Ordered Dithering
 ChangePixelFormat_Indexed_OldDithering = Indexed with Old Dithering
-ChangePixelFormat_Indexed_ErrorDiffusion = Indexed with Floyd-Steinberg Error Diffusion Dithering
+ChangePixelFormat_Indexed_FloydSteinberg = Indexed with Floyd-Steinberg Error Diffusion Dithering
+ChangePixelFormat_Indexed_JarvisJudiceNinke = Indexed with Jarvis-Judice-Ninke Error Diffusion Dithering
+ChangePixelFormat_Indexed_Stucki = Indexed with Stucki Error Diffusion Dithering
+ChangePixelFormat_Indexed_Atkinson = Indexed with Atkinson Error Diffusion Dithering
+ChangePixelFormat_Indexed_Burkes = Indexed with Burkes Error Diffusion Dithering
+ChangePixelFormat_Indexed_Sierra = Indexed with Sierra Error Diffusion Dithering
 ChangePixelFormat_MoreOptions = More Options
+ChangePixelFormat_ZigZag = Zig Zag
 Clear = Clear
 ClearCel = Clear Cel
 ClearRecentFiles = Clear Recent Files
@@ -516,6 +522,11 @@ no_dithering = No Dithering
 old_dithering = Old Dithering +\s
 ordered_dithering = Ordered Dithering +\s
 floyd_steinberg = Floyd-Steinberg Error Diffusion Dithering
+jarvis_judice_ninke = Jarvis Judice Ninke Error Diffusion Dithering
+stucki = Stucki Error Diffusion Dithering
+atkinson = Atkinson Error Diffusion Dithering
+burkes = Burkes Error Diffusion Dithering
+sierra = Sierra Error Diffusion Dithering
 
 [canvas_size]
 title = Canvas Size

src/app/cli/cli_processor.cpp

@@ -447,19 +447,13 @@ int CliProcessor::process(Context* ctx)
         }
         // --dithering-algorithm <algorithm>
         else if (opt == &m_options.ditheringAlgorithm()) {
-          if (value.value() == "none")
-            ditheringAlgorithm = render::DitheringAlgorithm::None;
-          else if (value.value() == "ordered")
-            ditheringAlgorithm = render::DitheringAlgorithm::Ordered;
-          else if (value.value() == "old")
-            ditheringAlgorithm = render::DitheringAlgorithm::Old;
-          else if (value.value() == "error-diffusion")
-            ditheringAlgorithm = render::DitheringAlgorithm::ErrorDiffusion;
-          else
+          ditheringAlgorithm = render::DitheringAlgorithmFromString(value.value());
+          if (ditheringAlgorithm == render::DitheringAlgorithm::Unknown) {
             throw std::runtime_error(
               "--dithering-algorithm needs a valid algorithm name\n"
               "Usage: --dithering-algorithm <algorithm>\n"
-              "Where <algorithm> can be none, ordered, old, or error-diffusion");
+              "Where <algorithm> can be: none, ordered, old, floyd-steinberg, jarvis-judice-ninke, stucki, atkinson, burkes or sierra.");
+          }
         }
         // --dithering-matrix <id>
         else if (opt == &m_options.ditheringMatrix()) {
@@ -477,15 +471,7 @@ int CliProcessor::process(Context* ctx)
           }
           else if (value.value() == "indexed") {
             params.set("format", "indexed");
-            switch (ditheringAlgorithm) {
-              case render::DitheringAlgorithm::None:    params.set("dithering", "none"); break;
-              case render::DitheringAlgorithm::Ordered: params.set("dithering", "ordered"); break;
-              case render::DitheringAlgorithm::Old:     params.set("dithering", "old"); break;
-              case render::DitheringAlgorithm::ErrorDiffusion:
-                params.set("dithering", "error-diffusion");
-                break;
-            }
-
+            params.set("dithering", DitheringAlgorithmToString(ditheringAlgorithm).c_str());
             if (ditheringAlgorithm != render::DitheringAlgorithm::None &&
                 !ditheringMatrix.empty()) {
               params.set("dithering-matrix", ditheringMatrix.c_str());

src/app/commands/cmd_change_pixel_format.cpp

@@ -41,6 +41,7 @@
 #include "render/quantization.h"
 #include "render/render.h"
 #include "render/task_delegate.h"
+#include "ui/button.h"
 #include "ui/listitem.h"
 #include "ui/paint_event.h"
 #include "ui/size_hint_event.h"
@@ -177,6 +178,7 @@ public:
     , m_imageBuffer(new doc::ImageBuffer)
     , m_selectedItem(nullptr)
     , m_ditheringSelector(nullptr)
+    , m_zigZagCheck(nullptr)
     , m_mapAlgorithmSelector(nullptr)
     , m_bestFitCriteriaSelector(nullptr)
     , m_imageJustCreated(true)
@@ -204,6 +206,8 @@ public:
       m_ditheringSelector = new DitheringSelector(DitheringSelector::SelectBoth);
       m_ditheringSelector->setExpansive(true);
 
+      m_zigZagCheck = new CheckBox(Strings::commands_ChangePixelFormat_ZigZag());
+
       m_mapAlgorithmSelector = new RgbMapAlgorithmSelector;
       m_mapAlgorithmSelector->setExpansive(true);
 
@@ -217,6 +221,9 @@ public:
           m_ditheringSelector->setSelectedItemIndex(index);
       }
 
+      // Select default zig zag
+      m_zigZagCheck->setSelected(pref.quantization.zigZag());
+
       // Select default RgbMap algorithm
       m_mapAlgorithmSelector->algorithm(pref.quantization.rgbmapAlgorithm());
 
@@ -224,6 +231,7 @@ public:
       m_bestFitCriteriaSelector->criteria(pref.quantization.fitCriteria());
 
       ditheringPlaceholder()->addChild(m_ditheringSelector);
+      ditheringPlaceholder()->addChild(m_zigZagCheck);
       rgbmapAlgorithmPlaceholder()->addChild(m_mapAlgorithmSelector);
       bestFitCriteriaPlaceholder()->addChild(m_bestFitCriteriaSelector);
 
@@ -233,6 +241,7 @@ public:
 
       // Signals
       m_ditheringSelector->Change.connect([this] { onIndexParamChange(); });
+      m_zigZagCheck->Click.connect([this] { onIndexParamChange(); });
       m_mapAlgorithmSelector->Change.connect([this] { onIndexParamChange(); });
       m_bestFitCriteriaSelector->Change.connect([this] { onIndexParamChange(); });
       factor()->Change.connect([this] { onIndexParamChange(); });
@@ -281,6 +290,7 @@ public:
     if (m_ditheringSelector) {
       d.algorithm(m_ditheringSelector->ditheringAlgorithm());
       d.matrix(m_ditheringSelector->ditheringMatrix());
+      d.zigzag(m_zigZagCheck->isSelected());
     }
     d.factor(double(factor()->getValue()) / 100.0);
     return d;
@@ -317,16 +327,16 @@ public:
   {
     auto& pref = Preferences::instance();
 
-    // Save the dithering method used for the future
+    // Save the dithering method and zig-zag setting used for the future
     if (m_ditheringSelector) {
       if (auto item = m_ditheringSelector->getSelectedItem()) {
         pref.quantization.ditheringAlgorithm(item->text());
 
-        if (m_ditheringSelector->ditheringAlgorithm() ==
-            render::DitheringAlgorithm::ErrorDiffusion) {
+        if (DitheringAlgorithmIsDiffusion(m_ditheringSelector->ditheringAlgorithm()))
           pref.quantization.ditheringFactor(factor()->getValue());
       }
-      }
+
+      pref.quantization.zigZag(m_zigZagCheck->isEnabled());
     }
 
     if (m_mapAlgorithmSelector || m_bestFitCriteriaSelector)
@@ -364,9 +374,10 @@ private:
     if (m_ditheringSelector) {
       const bool toIndexed = (dstColorMode == doc::ColorMode::INDEXED);
       m_ditheringSelector->setVisible(toIndexed);
+      m_zigZagCheck->setVisible(toIndexed);
 
-      const bool errorDiff = (m_ditheringSelector->ditheringAlgorithm() ==
-                              render::DitheringAlgorithm::ErrorDiffusion);
+      const bool errorDiff =
+        (render::DitheringAlgorithmIsDiffusion(m_ditheringSelector->ditheringAlgorithm()));
       amount()->setVisible(toIndexed && errorDiff);
     }
 
@@ -460,6 +471,7 @@ private:
   std::unique_ptr<ConvertThread> m_bgThread;
   ConversionItem* m_selectedItem;
   DitheringSelector* m_ditheringSelector;
+  CheckBox* m_zigZagCheck;
   RgbMapAlgorithmSelector* m_mapAlgorithmSelector;
   BestFitCriteriaSelector* m_bestFitCriteriaSelector;
   bool m_imageJustCreated;
@@ -487,6 +499,11 @@ struct ChangePixelFormatParams : public NewParams {
     1.0,
     { "ditheringFactor", "dithering-factor" }
   };
+  Param<bool> zigZag{
+    this,
+    true,
+    { "zigZag", "zig-zag" }
+  };
   Param<doc::RgbMapAlgorithm> rgbmap{ this, RgbMapAlgorithm::DEFAULT, "rgbmap" };
   Param<gen::ToGrayAlgorithm> toGray{ this, gen::ToGrayAlgorithm::DEFAULT, "toGray" };
   Param<doc::FitCriteria> fitCriteria{ this, doc::FitCriteria::DEFAULT, "fitCriteria" };
@@ -568,10 +585,13 @@ void ChangePixelFormatCommand::onExecute(Context* ctx)
     if (window.closer() != window.ok())
       return;
 
+    const auto d = window.dithering();
+
     params().colorMode(window.selectedColorMode());
-    params().dithering(window.dithering().algorithm());
-    matrix = window.dithering().matrix();
-    params().factor(window.dithering().factor());
+    params().dithering(d.algorithm());
+    matrix = d.matrix();
+    params().factor(d.factor());
+    params().zigZag(d.zigzag());
     params().rgbmap(window.rgbMapAlgorithm());
     params().fitCriteria(window.fitCriteria());
     params().toGray(window.toGray());
@@ -615,9 +635,10 @@ void ChangePixelFormatCommand::onExecute(Context* ctx)
     }
 
     job.startJobWithCallback([this, &job, sprite, &matrix](Tx& tx) {
-      tx(new cmd::SetPixelFormat(sprite,
+      tx(new cmd::SetPixelFormat(
+        sprite,
         (PixelFormat)params().colorMode(),
-                                 render::Dithering(params().dithering(), matrix, params().factor()),
+        render::Dithering(params().dithering(), matrix, params().zigZag(), params().factor()),
         params().rgbmap(),
         get_gray_func(params().toGray()),
         &job, // SpriteJob is a render::TaskDelegate
@@ -651,8 +672,23 @@ std::string ChangePixelFormatCommand::onGetFriendlyName() const
           case render::DitheringAlgorithm::Old:
             conversion = Strings::commands_ChangePixelFormat_Indexed_OldDithering();
             break;
-          case render::DitheringAlgorithm::ErrorDiffusion:
-            conversion = Strings::commands_ChangePixelFormat_Indexed_ErrorDiffusion();
+          case render::DitheringAlgorithm::FloydSteinberg:
+            conversion = Strings::commands_ChangePixelFormat_Indexed_FloydSteinberg();
+            break;
+          case render::DitheringAlgorithm::JarvisJudiceNinke:
+            conversion = Strings::commands_ChangePixelFormat_Indexed_JarvisJudiceNinke();
+            break;
+          case render::DitheringAlgorithm::Stucki:
+            conversion = Strings::commands_ChangePixelFormat_Indexed_Stucki();
+            break;
+          case render::DitheringAlgorithm::Atkinson:
+            conversion = Strings::commands_ChangePixelFormat_Indexed_Atkinson();
+            break;
+          case render::DitheringAlgorithm::Burkes:
+            conversion = Strings::commands_ChangePixelFormat_Indexed_Burkes();
+            break;
+          case render::DitheringAlgorithm::Sierra:
+            conversion = Strings::commands_ChangePixelFormat_Indexed_Sierra();
             break;
         }
         break;

src/app/commands/new_params.cpp

@@ -275,14 +275,10 @@ void Param<doc::FitCriteria>::fromString(const std::string& value)
 template<>
 void Param<render::DitheringAlgorithm>::fromString(const std::string& value)
 {
-  if (base::utf8_icmp(value, "ordered") == 0)
-    setValue(render::DitheringAlgorithm::Ordered);
-  else if (base::utf8_icmp(value, "old") == 0)
-    setValue(render::DitheringAlgorithm::Old);
-  else if (base::utf8_icmp(value, "error-diffusion") == 0)
-    setValue(render::DitheringAlgorithm::ErrorDiffusion);
-  else
-    setValue(render::DitheringAlgorithm::None);
+  auto algo = render::DitheringAlgorithmFromString(value);
+  if (algo == render::DitheringAlgorithm::Unknown)
+    algo = render::DitheringAlgorithm::None;
+  setValue(algo);
 }
 
 template<>

src/app/ui/context_bar.cpp

@@ -2577,8 +2577,26 @@ render::DitheringAlgorithmBase* ContextBar::ditheringAlgorithm()
     case render::DitheringAlgorithm::None:    s_dither.reset(nullptr); break;
     case render::DitheringAlgorithm::Ordered: s_dither.reset(new render::OrderedDither2(-1)); break;
     case render::DitheringAlgorithm::Old:     s_dither.reset(new render::OrderedDither(-1)); break;
-    case render::DitheringAlgorithm::ErrorDiffusion:
-      s_dither.reset(new render::ErrorDiffusionDither(-1));
+    case render::DitheringAlgorithm::FloydSteinberg:
+      s_dither.reset(
+        new render::ErrorDiffusionDither(render::ErrorDiffusionType::FloydSteinberg, -1));
+      break;
+    case render::DitheringAlgorithm::JarvisJudiceNinke:
+      s_dither.reset(
+        new render::ErrorDiffusionDither(render::ErrorDiffusionType::JarvisJudiceNinke, -1));
+      break;
+    case render::DitheringAlgorithm::Stucki:
+      s_dither.reset(new render::ErrorDiffusionDither(render::ErrorDiffusionType::Stucki, -1));
+      break;
+    case render::DitheringAlgorithm::Atkinson:
+      s_dither.reset(new render::ErrorDiffusionDither(render::ErrorDiffusionType::Atkinson, -1));
+      break;
+    case render::DitheringAlgorithm::Burkes:
+      s_dither.reset(new render::ErrorDiffusionDither(render::ErrorDiffusionType::Burkes, -1));
+      break;
+    case render::DitheringAlgorithm::Sierra:
+      s_dither.reset(new render::ErrorDiffusionDither(render::ErrorDiffusionType::Sierra, -1));
+      break;
       break;
   }
 

src/app/ui/dithering_selector.cpp

@@ -231,9 +231,24 @@ void DitheringSelector::regenerate(int selectedItemIndex)
           Console::showException(e);
         }
       }
-      addItem(new DitherItem(render::DitheringAlgorithm::ErrorDiffusion,
+      addItem(new DitherItem(render::DitheringAlgorithm::FloydSteinberg,
                              render::DitheringMatrix(),
                              Strings::dithering_selector_floyd_steinberg()));
+      addItem(new DitherItem(render::DitheringAlgorithm::JarvisJudiceNinke,
+                             render::DitheringMatrix(),
+                             Strings::dithering_selector_jarvis_judice_ninke()));
+      addItem(new DitherItem(render::DitheringAlgorithm::Stucki,
+                             render::DitheringMatrix(),
+                             Strings::dithering_selector_stucki()));
+      addItem(new DitherItem(render::DitheringAlgorithm::Atkinson,
+                             render::DitheringMatrix(),
+                             Strings::dithering_selector_atkinson()));
+      addItem(new DitherItem(render::DitheringAlgorithm::Burkes,
+                             render::DitheringMatrix(),
+                             Strings::dithering_selector_burkes()));
+      addItem(new DitherItem(render::DitheringAlgorithm::Sierra,
+                             render::DitheringMatrix(),
+                             Strings::dithering_selector_sierra()));
       break;
     case SelectMatrix:
       addItem(

src/app/ui/editor/editor.cpp

@@ -58,6 +58,7 @@
 #include "app/util/tile_flags_utils.h"
 #include "base/chrono.h"
 #include "base/convert_to.h"
+#include "base/scoped_value.h"
 #include "doc/doc.h"
 #include "doc/mask_boundaries.h"
 #include "doc/slice.h"
@@ -266,6 +267,23 @@ void Editor::setStateInternal(const EditorStatePtr& newState)
 {
   m_brushPreview.hide();
 
+  // Some onLeaveState impls (like the ones from MovingPixelsState,
+  // WritingTextState, MovingSelectionState) might generate a
+  // Tx/Transaction::commit(), which will add a new undo state,
+  // triggering a sprite change scripting event
+  // (SpriteEvents::onAddUndoState). This event could be handled by an
+  // extension and that extension might want to save the current
+  // sprite (e.g. calling Sprite_saveCopyAs, the kind of extension
+  // that takes snapshots after each sprite change). That will be a
+  // new Context::executeCommand() for the save command, generating a
+  // BeforeCommandExecution signal, getting back to onLeaveState
+  // again. In that case, we just ignore the reentry as the first
+  // onLeaveState should handle everything (to avoid an stack
+  // overflow/infinite recursion).
+  if (m_leavingState)
+    return;
+  base::ScopedValue leaving(m_leavingState, true);
+
   // Fire before change state event, set the state, and fire after
   // change state event.
   EditorState::LeaveAction leaveAction = m_state->onLeaveState(this, newState.get());

src/app/ui/editor/editor.h

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2018-2024  Igara Studio S.A.
+// Copyright (C) 2018-2025  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -458,6 +458,13 @@ private:
 
   DocView* m_docView;
 
+  // Special flag to avoid re-entering a new state when we are leaving
+  // the current one. This avoids an infinite onLeaveState() recursion
+  // in some special cases when an extension (third-party code)
+  // creates a new sprite change in the same sprite change scripting
+  // event.
+  bool m_leavingState = false;
+
   // Last known mouse position received by this editor when the
   // mouse button was pressed. Used for auto-scrolling. To get the
   // current mouse position on the editor you can use

src/render/CMakeLists.txt

@@ -3,6 +3,7 @@
 # Copyright (C) 2001-2018 David Capello
 
 add_library(render-lib
+  dithering_algorithm.cpp
   error_diffusion.cpp
   get_sprite_pixel.cpp
   gradient.cpp

src/render/dithering.h

@@ -18,24 +18,29 @@ class Dithering {
 public:
   Dithering(DitheringAlgorithm algorithm = DitheringAlgorithm::None,
             const DitheringMatrix& matrix = DitheringMatrix(),
+            bool zigzag = true,
             double factor = 1.0)
     : m_algorithm(algorithm)
     , m_matrix(matrix)
+    , m_zigzag(zigzag)
     , m_factor(factor)
   {
   }
 
   DitheringAlgorithm algorithm() const { return m_algorithm; }
   DitheringMatrix matrix() const { return m_matrix; }
+  bool zigzag() const { return m_zigzag; }
   double factor() const { return m_factor; }
 
   void algorithm(const DitheringAlgorithm algorithm) { m_algorithm = algorithm; }
   void matrix(const DitheringMatrix& matrix) { m_matrix = matrix; }
+  void zigzag(bool zigzag) { m_zigzag = zigzag; }
   void factor(const double factor) { m_factor = factor; }
 
 private:
   DitheringAlgorithm m_algorithm;
   DitheringMatrix m_matrix;
+  bool m_zigzag;
   double m_factor;
 };
 

src/render/dithering_algorithm.cpp

@@ -0,0 +1,53 @@
+// Aseprite
+// Copyright (C) 2025 Igara Studio S.A.
+//
+// This program is distributed under the terms of
+// the End-User License Agreement for Aseprite.
+
+#include <algorithm>
+#include <string>
+#include <unordered_map>
+
+#include "base/string.h"
+#include "render/dithering_algorithm.h"
+
+namespace render {
+
+static const std::unordered_map<DitheringAlgorithm, std::string> names = {
+  { DitheringAlgorithm::None,              "none"                },
+  { DitheringAlgorithm::Ordered,           "ordered"             },
+  { DitheringAlgorithm::Old,               "old"                 },
+  { DitheringAlgorithm::FloydSteinberg,    "floyd-steinberg"     },
+  { DitheringAlgorithm::FloydSteinberg,    "error-diffusion"     }, // alias
+  { DitheringAlgorithm::JarvisJudiceNinke, "jarvis-judice-ninke" },
+  { DitheringAlgorithm::Stucki,            "stucki"              },
+  { DitheringAlgorithm::Atkinson,          "atkinson"            },
+  { DitheringAlgorithm::Burkes,            "burkes"              },
+  { DitheringAlgorithm::Sierra,            "sierra"              },
+};
+
+bool DitheringAlgorithmIsDiffusion(DitheringAlgorithm algo)
+{
+  switch (algo) {
+    case DitheringAlgorithm::None:
+    case DitheringAlgorithm::Ordered:
+    case DitheringAlgorithm::Old:     return false;
+    default:                          return true;
+  }
+}
+
+std::string DitheringAlgorithmToString(DitheringAlgorithm algo)
+{
+  auto it = names.find(algo);
+  return (it != names.end()) ? it->second : "unknown";
+}
+
+DitheringAlgorithm DitheringAlgorithmFromString(const std::string& name)
+{
+  auto it = std::find_if(names.begin(), names.end(), [name](const auto& pair) {
+    return base::utf8_icmp(pair.second, name) == 0;
+  });
+  return (it != names.end()) ? it->first : DitheringAlgorithm::Unknown;
+}
+
+} // namespace render

src/render/dithering_algorithm.h

@@ -9,6 +9,8 @@
 #define RENDER_DITHERING_METHOD_H_INCLUDED
 #pragma once
 
+#include <string>
+
 namespace render {
 
 // Dithering algorithms
@@ -16,9 +18,19 @@ enum class DitheringAlgorithm {
   None,
   Ordered,
   Old,
-  ErrorDiffusion,
+  FloydSteinberg,
+  JarvisJudiceNinke,
+  Stucki,
+  Atkinson,
+  Burkes,
+  Sierra,
+  Unknown
 };
 
+bool DitheringAlgorithmIsDiffusion(DitheringAlgorithm algo);
+std::string DitheringAlgorithmToString(DitheringAlgorithm algo);
+DitheringAlgorithm DitheringAlgorithmFromString(const std::string& name);
+
 } // namespace render
 
 #endif

src/render/error_diffusion.cpp

@@ -15,12 +15,119 @@
 #include "gfx/rgb.h"
 
 #include <algorithm>
+#include <vector>
 
 namespace render {
 
-ErrorDiffusionDither::ErrorDiffusionDither(int transparentIndex)
-  : m_transparentIndex(transparentIndex)
+// Predefined error diffusion algorithms
+class ErrorDiffusionMatrices {
+public:
+  static const ErrorDiffusionMatrix& getFloydSteinberg()
   {
+    static const ErrorDiffusionMatrix matrix(3,
+                                             2,
+                                             1,
+                                             0,
+                                             {
+                                               { 0, 0, 7 },
+                                               { 3, 5, 1 }
+    },
+                                             16);
+    return matrix;
+  }
+
+  static const ErrorDiffusionMatrix& getJarvisJudiceNinke()
+  {
+    static const ErrorDiffusionMatrix matrix(5,
+                                             3,
+                                             2,
+                                             0,
+                                             {
+                                               { 0, 0, 0, 7, 5 },
+                                               { 3, 5, 7, 5, 3 },
+                                               { 1, 3, 5, 3, 1 }
+    },
+                                             48);
+    return matrix;
+  }
+
+  static const ErrorDiffusionMatrix& getStucki()
+  {
+    static const ErrorDiffusionMatrix matrix(5,
+                                             3,
+                                             2,
+                                             0,
+                                             {
+                                               { 0, 0, 0, 8, 4 },
+                                               { 2, 4, 8, 4, 2 },
+                                               { 1, 2, 4, 2, 1 }
+    },
+                                             42);
+    return matrix;
+  }
+
+  static const ErrorDiffusionMatrix& getAtkinson()
+  {
+    static const ErrorDiffusionMatrix matrix(4,
+                                             3,
+                                             1,
+                                             0,
+                                             {
+                                               { 0, 0, 1, 1 },
+                                               { 1, 1, 1, 0 },
+                                               { 0, 1, 0, 0 }
+    },
+                                             8);
+    return matrix;
+  }
+
+  static const ErrorDiffusionMatrix& getBurkes()
+  {
+    static const ErrorDiffusionMatrix matrix(5,
+                                             2,
+                                             2,
+                                             0,
+                                             {
+                                               { 0, 0, 0, 8, 4 },
+                                               { 2, 4, 8, 4, 2 }
+    },
+                                             32);
+    return matrix;
+  }
+
+  static const ErrorDiffusionMatrix& getSierra()
+  {
+    static const ErrorDiffusionMatrix matrix(5,
+                                             3,
+                                             2,
+                                             0,
+                                             {
+                                               { 0, 0, 0, 5, 3 },
+                                               { 2, 4, 5, 4, 2 },
+                                               { 0, 2, 3, 2, 0 }
+    },
+                                             32);
+    return matrix;
+  }
+};
+
+ErrorDiffusionDither::ErrorDiffusionDither(ErrorDiffusionType type, int transparentIndex)
+  : m_transparentIndex(transparentIndex)
+  , m_diffusionType(type)
+{
+}
+
+const ErrorDiffusionMatrix& ErrorDiffusionDither::getCurrentMatrix() const
+{
+  switch (m_diffusionType) {
+    case ErrorDiffusionType::JarvisJudiceNinke:
+      return ErrorDiffusionMatrices::getJarvisJudiceNinke();
+    case ErrorDiffusionType::Stucki:         return ErrorDiffusionMatrices::getStucki();
+    case ErrorDiffusionType::Atkinson:       return ErrorDiffusionMatrices::getAtkinson();
+    case ErrorDiffusionType::Burkes:         return ErrorDiffusionMatrices::getBurkes();
+    case ErrorDiffusionType::Sierra:         return ErrorDiffusionMatrices::getSierra();
+    case ErrorDiffusionType::FloydSteinberg: return ErrorDiffusionMatrices::getFloydSteinberg();
+  }
 }
 
 void ErrorDiffusionDither::start(const doc::Image* srcImage,
@@ -29,9 +136,18 @@ void ErrorDiffusionDither::start(const doc::Image* srcImage,
 {
   m_srcImage = srcImage;
   m_width = 2 + srcImage->width();
+
+  // Get the current matrix to determine buffer size needed
+  const ErrorDiffusionMatrix& matrix = getCurrentMatrix();
+  const int bufferRows = matrix.height;
+
+  // Resize error buffers to accommodate the matrix height
+  const std::vector<int>::size_type bufferSize = m_width * bufferRows;
   for (int i = 0; i < kChannels; ++i)
-    m_err[i].resize(m_width * 2, 0);
+    m_err[i].resize(bufferSize, 0);
+
   m_lastY = -1;
+  m_currentRowOffset = 0;
   m_factor = int(factor * 100.0);
 }
 
@@ -42,30 +158,39 @@ void ErrorDiffusionDither::finish()
 doc::color_t ErrorDiffusionDither::ditherRgbToIndex2D(const int x,
                                                       const int y,
                                                       const doc::RgbMap* rgbmap,
-                                                      const doc::Palette* palette)
+                                                      const doc::Palette* palette,
+                                                      const int direction)
 {
+  const ErrorDiffusionMatrix& matrix = getCurrentMatrix();
+
   if (y != m_lastY) {
-    for (int i = 0; i < kChannels; ++i) {
-      int* row0 = &m_err[i][0];
-      int* row1 = row0 + m_width;
-      int* end1 = row1 + m_width;
-      std::copy(row1, end1, row0);
-      std::fill(row1, end1, 0);
+    // Instead of shifting all rows, just advance the circular buffer
+    // and clear the row that will be reused
+    m_currentRowOffset = (m_currentRowOffset + 1) % matrix.height;
+
+    // Clear only the row that will be used as the "last" row
+    const int clearRowIndex = (m_currentRowOffset + matrix.height - 1) % matrix.height;
+    for (int c = 0; c < kChannels; ++c) {
+      int* rowToClear = &m_err[c][m_width * clearRowIndex];
+      std::fill(rowToClear, rowToClear + m_width, 0);
     }
+
     m_lastY = y;
   }
 
   doc::color_t color = doc::get_pixel_fast<doc::RgbTraits>(m_srcImage, x, y);
 
-  // Get RGB values + quatization error
+  // Get RGB values + quantization error
   int v[kChannels] = { doc::rgba_getr(color),
                        doc::rgba_getg(color),
                        doc::rgba_getb(color),
                        doc::rgba_geta(color) };
-  for (int i = 0; i < kChannels; ++i) {
-    v[i] += m_err[i][x + 1];
-    v[i] = std::clamp(v[i], 0, 255);
-  }
+
+  // Add accumulated error (16-bit fixed point) and convert to 0..255
+  for (int c = 0; c < kChannels; ++c)
+    v[c] = std::clamp(((v[c] << 16) + m_err[c][m_width * m_currentRowOffset + x + 1] + 32767) >> 16,
+                      0,
+                      255);
 
   const doc::color_t index = (rgbmap ?
                                 rgbmap->mapColor(v[0], v[1], v[2], v[3]) :
@@ -82,26 +207,36 @@ doc::color_t ErrorDiffusionDither::ditherRgbToIndex2D(const int x,
                                       v[2] - doc::rgba_getb(palColor),
                                       v[3] - doc::rgba_geta(palColor) };
 
-  // TODO using Floyd-Steinberg matrix here but it should be configurable
-  for (int i = 0; i < kChannels; ++i) {
-    int* err = &m_err[i][x];
-    const int q = quantError[i] * m_factor / 100;
-    const int a = q * 7 / 16;
-    const int b = q * 3 / 16;
-    const int c = q * 5 / 16;
-    const int d = q * 1 / 16;
+  const int srcWidth = m_srcImage->width();
 
-    if (y & 1) {
-      err[0] += a;
-      err[m_width + 2] += b;
-      err[m_width + 1] += c;
-      err[m_width] += d;
+  // Distribute error using the configurable matrix
+  for (int c = 0; c < kChannels; ++c) {
+    const int qerr = quantError[c] * m_factor / 100;
+
+    for (int my = 0; my < matrix.height; ++my) {
+      // Use circular buffer indexing
+      const int bufferRow = (m_currentRowOffset + my) % matrix.height;
+      const int bufferRowIndex = bufferRow * m_width;
+
+      for (int mx = 0; mx < matrix.width; ++mx) {
+        const int coeff = direction > 0 ? matrix.coefficients[my][mx] :
+                                          matrix.coefficients[my][matrix.width - 1 - mx];
+        if (coeff == 0)
+          continue;
+
+        const int errorPixelX = x + mx - matrix.centerX;
+        const int errorPixelY = y + my - matrix.centerY;
+
+        // Check bounds
+        if (errorPixelX < 0 || errorPixelX >= srcWidth)
+          continue;
+        if (errorPixelY < y)
+          continue; // Don't go backwards
+
+        // Calculate error as 16-bit fixed point
+        const int errorValue = ((qerr * coeff) << 16) / matrix.divisor;
+        m_err[c][bufferRowIndex + errorPixelX + 1] += errorValue;
       }
-    else {
-      err[+2] += a;
-      err[m_width] += b;
-      err[m_width + 1] += c;
-      err[m_width + 2] += d;
     }
   }
 

src/render/error_diffusion.h

@@ -16,22 +16,58 @@
 
 namespace render {
 
+enum class ErrorDiffusionType : uint8_t {
+  FloydSteinberg,
+  JarvisJudiceNinke,
+  Stucki,
+  Atkinson,
+  Burkes,
+  Sierra
+};
+
+// Error diffusion matrix structure
+struct ErrorDiffusionMatrix {
+  int width, height;
+  int centerX, centerY;
+  std::vector<std::vector<int>> coefficients;
+  int divisor;
+
+  ErrorDiffusionMatrix(int w,
+                       int h,
+                       int cx,
+                       int cy,
+                       const std::vector<std::vector<int>>& coeff,
+                       int div)
+    : width(w)
+    , height(h)
+    , centerX(cx)
+    , centerY(cy)
+    , coefficients(coeff)
+    , divisor(div)
+  {
+  }
+};
+
 class ErrorDiffusionDither : public DitheringAlgorithmBase {
 public:
-  ErrorDiffusionDither(int transparentIndex = -1);
+  ErrorDiffusionDither(ErrorDiffusionType type, int transparentIndex);
   int dimensions() const override { return 2; }
-  bool zigZag() const override { return true; }
   void start(const doc::Image* srcImage, doc::Image* dstImage, const double factor) override;
   void finish() override;
   doc::color_t ditherRgbToIndex2D(const int x,
                                   const int y,
                                   const doc::RgbMap* rgbmap,
-                                  const doc::Palette* palette) override;
+                                  const doc::Palette* palette,
+                                  const int direction) override;
 
 private:
+  const ErrorDiffusionMatrix& getCurrentMatrix() const;
+
   int m_transparentIndex;
+  ErrorDiffusionType m_diffusionType;
   const doc::Image* m_srcImage;
   int m_width, m_lastY;
+  int m_currentRowOffset;
   static const int kChannels = 4;
   std::vector<int> m_err[kChannels];
   int m_factor;

src/render/ordered_dither.cpp

@@ -240,47 +240,38 @@ void dither_rgb_image_to_indexed(DitheringAlgorithmBase& algorithm,
         ASSERT(srcIt != srcBits.end());
         ASSERT(dstIt != dstBits.end());
         *dstIt = algorithm.ditherRgbPixelToIndex(dithering.matrix(), *srcIt, x, y, rgbmap, palette);
+      }
 
       if (delegate) {
         if (!delegate->continueTask())
           return;
-        }
-      }
-
-      if (delegate) {
         delegate->notifyTaskProgress(double(y + 1) / double(h));
       }
     }
   }
   else {
     auto dstIt = doc::get_pixel_address_fast<doc::IndexedTraits>(dstImage, 0, 0);
-    const bool zigZag = algorithm.zigZag();
+    auto zigZag = dithering.zigzag();
 
     for (int y = 0; y < h; ++y) {
       if (zigZag && (y & 1)) { // Odd row: go from right-to-left
         dstIt += w - 1;
         for (int x = w - 1; x >= 0; --x, --dstIt) {
           ASSERT(dstIt == doc::get_pixel_address_fast<doc::IndexedTraits>(dstImage, x, y));
-          *dstIt = algorithm.ditherRgbToIndex2D(x, y, rgbmap, palette);
-          if (delegate) {
-            if (!delegate->continueTask())
-              return;
-          }
+          *dstIt = algorithm.ditherRgbToIndex2D(x, y, rgbmap, palette, -1);
         }
         dstIt += w + 1;
       }
-      else { // Even row: go fromo left-to-right
+      else { // Even row: go from left-to-right
         for (int x = 0; x < w; ++x, ++dstIt) {
           ASSERT(dstIt == doc::get_pixel_address_fast<doc::IndexedTraits>(dstImage, x, y));
-          *dstIt = algorithm.ditherRgbToIndex2D(x, y, rgbmap, palette);
+          *dstIt = algorithm.ditherRgbToIndex2D(x, y, rgbmap, palette, +1);
+        }
+      }
 
       if (delegate) {
         if (!delegate->continueTask())
           return;
-          }
-        }
-      }
-      if (delegate) {
         delegate->notifyTaskProgress(double(y + 1) / double(h));
       }
     }

src/render/ordered_dither.h

@@ -27,7 +27,6 @@ public:
   virtual ~DitheringAlgorithmBase() {}
 
   virtual int dimensions() const { return 1; }
-  virtual bool zigZag() const { return false; }
 
   virtual void start(const doc::Image* srcImage, doc::Image* dstImage, const double factor) {}
 
@@ -46,7 +45,8 @@ public:
   virtual doc::color_t ditherRgbToIndex2D(const int x,
                                           const int y,
                                           const doc::RgbMap* rgbmap,
-                                          const doc::Palette* palette)
+                                          const doc::Palette* palette,
+                                          const int direction)
   {
     return 0;
   }

src/render/quantization.cpp

@@ -159,8 +159,29 @@ Image* convert_pixel_format(const Image* image,
       case DitheringAlgorithm::Old:
         dither.reset(new OrderedDither(is_background ? -1 : new_mask_color));
         break;
-      case DitheringAlgorithm::ErrorDiffusion:
-        dither.reset(new ErrorDiffusionDither(is_background ? -1 : new_mask_color));
+      case DitheringAlgorithm::FloydSteinberg:
+        dither.reset(new ErrorDiffusionDither(ErrorDiffusionType::FloydSteinberg,
+                                              is_background ? -1 : new_mask_color));
+        break;
+      case DitheringAlgorithm::JarvisJudiceNinke:
+        dither.reset(new ErrorDiffusionDither(ErrorDiffusionType::JarvisJudiceNinke,
+                                              is_background ? -1 : new_mask_color));
+        break;
+      case DitheringAlgorithm::Stucki:
+        dither.reset(new ErrorDiffusionDither(ErrorDiffusionType::Stucki,
+                                              is_background ? -1 : new_mask_color));
+        break;
+      case DitheringAlgorithm::Atkinson:
+        dither.reset(new ErrorDiffusionDither(ErrorDiffusionType::Atkinson,
+                                              is_background ? -1 : new_mask_color));
+        break;
+      case DitheringAlgorithm::Burkes:
+        dither.reset(new ErrorDiffusionDither(ErrorDiffusionType::Burkes,
+                                              is_background ? -1 : new_mask_color));
+        break;
+      case DitheringAlgorithm::Sierra:
+        dither.reset(new ErrorDiffusionDither(ErrorDiffusionType::Sierra,
+                                              is_background ? -1 : new_mask_color));
         break;
     }
     if (dither)

src/render/quantization.h

@@ -1,4 +1,4 @@
-// Aseprite Rener Library
+// Aseprite Render Library
 // Copyright (c) 2019-2021  Igara Studio S.A.
 // Copyright (c) 2001-2017  David Capello
 //