diff --git a/data/widgets/gif_options.xml b/data/widgets/gif_options.xml
new file mode 100644
index 000000000..3c901c05e
--- /dev/null
+++ b/data/widgets/gif_options.xml
@@ -0,0 +1,30 @@
+<!-- Aseprite -->
+<!-- Copyright (C) 2014 by David Capello -->
+<gui>
+<window text="GIF Options" id="gif_options">
+  <vbox>
+    <vbox id="rgb_options">
+      <separator text="RGBA to Indexed Conversion:" left="true" horizontal="true" />
+      <check text="Enable Dithering" id="dither" />
+
+      <separator text="Optimize Color Palette:" left="true" horizontal="true" />
+      <radio id="quantize_each" text="&amp;One palette for each frame" group="1" />
+      <radio id="quantize_all" text="&amp;One palette for all frames" group="1" />
+      <radio id="no_quantize" text="&amp;Don't modify palettes" group="1" />
+    </vbox>
+
+    <separator text="Optimize for Web:" left="true" horizontal="true" />
+    <check text="Interlaced" id="interlaced" />
+
+    <separator horizontal="true" />
+
+    <hbox>
+      <boxfiller />
+      <hbox homogeneous="true">
+        <button text="&amp;OK" closewindow="true" id="ok" magnet="true" minwidth="60" />
+        <button text="&amp;Cancel" closewindow="true" />
+      </hbox>
+    </hbox>
+  </vbox>
+</window>
+</gui>
diff --git a/src/app/app.cpp b/src/app/app.cpp
index 148dda847..b3c5f33f8 100644
--- a/src/app/app.cpp
+++ b/src/app/app.cpp
@@ -214,7 +214,7 @@ int App::run()
            end = m_files.end();
          it != end; ++it) {
       // Load the sprite
-      Document* document = load_document(it->c_str());
+      Document* document = load_document(context, it->c_str());
       if (!document) {
         if (!isGui())
           console.printf("Error loading file \"%s\"\n", it->c_str());
diff --git a/src/app/commands/cmd_open_file.cpp b/src/app/commands/cmd_open_file.cpp
index 4859d6205..c1bc5e140 100644
--- a/src/app/commands/cmd_open_file.cpp
+++ b/src/app/commands/cmd_open_file.cpp
@@ -126,7 +126,7 @@ void OpenFileCommand::onExecute(Context* context)
   }
 
   if (!m_filename.empty()) {
-    base::UniquePtr<FileOp> fop(fop_to_load_document(m_filename.c_str(), FILE_LOAD_SEQUENCE_ASK));
+    base::UniquePtr<FileOp> fop(fop_to_load_document(context, m_filename.c_str(), FILE_LOAD_SEQUENCE_ASK));
     bool unrecent = false;
 
     if (fop) {
diff --git a/src/app/commands/cmd_palette_editor.cpp b/src/app/commands/cmd_palette_editor.cpp
index 4fcfabfa9..ce382de0a 100644
--- a/src/app/commands/cmd_palette_editor.cpp
+++ b/src/app/commands/cmd_palette_editor.cpp
@@ -587,7 +587,8 @@ void PaletteEntryEditor::onQuantizeClick(Event& ev)
       return;
     }
 
-    palette = quantization::create_palette_from_rgb(sprite, reader.frame());
+    palette = quantization::create_palette_from_rgb(
+      sprite, reader.frame(), NULL);
   }
 
   setNewPalette(palette, "Quantize Palette");
diff --git a/src/app/commands/cmd_save_file.cpp b/src/app/commands/cmd_save_file.cpp
index 1545f229d..9b40b5189 100644
--- a/src/app/commands/cmd_save_file.cpp
+++ b/src/app/commands/cmd_save_file.cpp
@@ -81,9 +81,9 @@ private:
   FileOp* m_fop;
 };
 
-static void save_document_in_background(Document* document, bool mark_as_saved)
+static void save_document_in_background(Context* context, Document* document, bool mark_as_saved)
 {
-  base::UniquePtr<FileOp> fop(fop_to_save_document(document));
+  base::UniquePtr<FileOp> fop(fop_to_save_document(context, document));
   if (!fop)
     return;
 
@@ -192,7 +192,7 @@ protected:
       m_selectedFilename = filename;
 
       // Save the document
-      save_document_in_background(documentWriter, markAsSaved);
+      save_document_in_background(writer.context(), documentWriter, markAsSaved);
 
       if (documentWriter->isModified())
         documentWriter->setFilename(oldFilename);
@@ -251,7 +251,7 @@ void SaveFileCommand::onExecute(Context* context)
     if (!confirmReadonly(documentWriter->getFilename()))
       return;
 
-    save_document_in_background(documentWriter, true);
+    save_document_in_background(context, documentWriter, true);
     update_screen_for_document(documentWriter);
   }
   // If the document isn't associated to a file, we must to show the
diff --git a/src/app/context.cpp b/src/app/context.cpp
index 9aeba559e..7b839dd25 100644
--- a/src/app/context.cpp
+++ b/src/app/context.cpp
@@ -32,6 +32,11 @@
 
 namespace app {
 
+Context::Context()
+  : m_settings(NULL)
+{
+}
+
 Context::Context(ISettings* settings)
   : m_settings(settings)
 {
@@ -159,4 +164,9 @@ void Context::onRemoveDocument(Document* document)
   m_observers.notifyRemoveDocument(this, document);
 }
 
+void Context::onGetActiveLocation(DocumentLocation* location) const
+{
+  // Without active location
+}
+
 } // namespace app
diff --git a/src/app/context.h b/src/app/context.h
index 1de054295..a1dde48b1 100644
--- a/src/app/context.h
+++ b/src/app/context.h
@@ -44,6 +44,9 @@ namespace app {
 
   class Context {
   public:
+    Context();
+    // The "settings" are deleted automatically in the ~Context destructor
+    Context(ISettings* settings);
     virtual ~Context();
 
     virtual bool isUiAvailable() const     { return false; }
@@ -76,19 +79,11 @@ namespace app {
     void removeObserver(ContextObserver* observer);
 
   protected:
-
-    // The "settings" are deleted automatically in the ~Context destructor
-    Context(ISettings* settings);
-
     virtual void onAddDocument(Document* document);
     virtual void onRemoveDocument(Document* document);
-    virtual void onGetActiveLocation(DocumentLocation* location) const = 0;
+    virtual void onGetActiveLocation(DocumentLocation* location) const;
 
   private:
-
-    // Without default constructor
-    Context();
-
     // List of all documents.
     Documents m_documents;
 
diff --git a/src/app/document.h b/src/app/document.h
index 149e0cc42..8ac8e326e 100644
--- a/src/app/document.h
+++ b/src/app/document.h
@@ -140,6 +140,7 @@ namespace app {
     // Loaded options from file
 
     void setFormatOptions(const SharedPtr<FormatOptions>& format_options);
+    SharedPtr<FormatOptions> getFormatOptions() { return m_format_options; }
 
     //////////////////////////////////////////////////////////////////////
     // Boundaries
diff --git a/src/app/document_api.cpp b/src/app/document_api.cpp
index 3c8141208..6f62a9e73 100644
--- a/src/app/document_api.cpp
+++ b/src/app/document_api.cpp
@@ -187,7 +187,7 @@ void DocumentApi::setPixelFormat(Sprite* sprite, PixelFormat newFormat, Ditherin
     }
 
     new_image = quantization::convert_pixel_format
-      (old_image, newFormat, dithering_method, rgbmap,
+      (old_image, NULL, newFormat, dithering_method, rgbmap,
        sprite->getPalette(frame),
        is_image_from_background);
 
diff --git a/src/app/document_exporter.cpp b/src/app/document_exporter.cpp
index 1e468d3e3..1b2ab67af 100644
--- a/src/app/document_exporter.cpp
+++ b/src/app/document_exporter.cpp
@@ -25,6 +25,7 @@
 #include "app/document.h"
 #include "app/document_api.h"
 #include "app/file/file.h"
+#include "app/ui_context.h"
 #include "base/compiler_specific.h"
 #include "base/path.h"
 #include "base/unique_ptr.h"
@@ -178,7 +179,7 @@ void DocumentExporter::exportSheet()
   // Save the image files.
   if (!m_textureFilename.empty()) {
     textureDocument->setFilename(m_textureFilename.c_str());
-    save_document(textureDocument.get());
+    save_document(UIContext::instance(), textureDocument.get());
   }
 }
 
diff --git a/src/app/file/file.cpp b/src/app/file/file.cpp
index ac5978395..85b40350e 100644
--- a/src/app/file/file.cpp
+++ b/src/app/file/file.cpp
@@ -22,8 +22,8 @@
 
 #include "app/file/file.h"
 
-#include "app/app.h"
 #include "app/console.h"
+#include "app/context.h"
 #include "app/document.h"
 #include "app/file/file_format.h"
 #include "app/file/file_formats_manager.h"
@@ -48,7 +48,7 @@ namespace app {
 
 using namespace base;
 
-static FileOp* fop_new(FileOpType type);
+static FileOp* fop_new(FileOpType type, Context* context);
 static void fop_prepare_for_sequence(FileOp* fop);
 
 static FileFormat* get_fileformat(const char* extension);
@@ -90,12 +90,12 @@ void get_writable_extensions(char* buf, int size)
   }
 }
 
-Document* load_document(const char* filename)
+Document* load_document(Context* context, const char* filename)
 {
   Document* document;
 
   /* TODO add a option to configure what to do with the sequence */
-  FileOp *fop = fop_to_load_document(filename, FILE_LOAD_SEQUENCE_NONE);
+  FileOp *fop = fop_to_load_document(context, filename, FILE_LOAD_SEQUENCE_NONE);
   if (!fop)
     return NULL;
 
@@ -116,10 +116,10 @@ Document* load_document(const char* filename)
   return document;
 }
 
-int save_document(Document* document)
+int save_document(Context* context, Document* document)
 {
   int ret;
-  FileOp* fop = fop_to_save_document(document);
+  FileOp* fop = fop_to_save_document(context, document);
   if (!fop)
     return -1;
 
@@ -138,11 +138,11 @@ int save_document(Document* document)
   return ret;
 }
 
-FileOp* fop_to_load_document(const char* filename, int flags)
+FileOp* fop_to_load_document(Context* context, const char* filename, int flags)
 {
   FileOp *fop;
 
-  fop = fop_new(FileOpLoad);
+  fop = fop_new(FileOpLoad, context);
   if (!fop)
     return NULL;
 
@@ -199,8 +199,7 @@ FileOp* fop_to_load_document(const char* filename, int flags)
       }
 
       /* TODO add a better dialog to edit file-names */
-      if ((flags & FILE_LOAD_SEQUENCE_ASK) &&
-          App::instance()->isGui()) {
+      if ((flags & FILE_LOAD_SEQUENCE_ASK) && context->isUiAvailable()) {
         /* really want load all files? */
         if ((fop->seq.filename_list.size() > 1) &&
             (ui::Alert::show("Notice"
@@ -231,12 +230,12 @@ done:;
   return fop;
 }
 
-FileOp* fop_to_save_document(Document* document)
+FileOp* fop_to_save_document(Context* context, Document* document)
 {
   FileOp *fop;
   bool fatal;
 
-  fop = fop_new(FileOpSave);
+  fop = fop_new(FileOpSave, context);
   if (!fop)
     return NULL;
 
@@ -323,7 +322,7 @@ FileOp* fop_to_save_document(Document* document)
   // Show the confirmation alert
   if (!warnings.empty()) {
     // Interative
-    if (App::instance()->isGui()) {
+    if (context->isUiAvailable()) {
       int ret;
 
       if (fatal)
@@ -663,8 +662,9 @@ void fop_post_load(FileOp* fop)
         fop->document->getSprite()->getPalettes().size() <= 1 &&
         fop->document->getSprite()->getPalette(FrameNumber(0))->isBlack()) {
       SharedPtr<Palette> palette
-        (quantization::create_palette_from_rgb(fop->document->getSprite(),
-                                               FrameNumber(0)));
+        (quantization::create_palette_from_rgb(
+          fop->document->getSprite(),
+          FrameNumber(0), NULL));
 
       fop->document->getSprite()->resetPalettes();
       fop->document->getSprite()->setPalette(palette, false);
@@ -802,13 +802,14 @@ bool fop_is_stop(FileOp *fop)
   return stop;
 }
 
-static FileOp* fop_new(FileOpType type)
+static FileOp* fop_new(FileOpType type, Context* context)
 {
   FileOp* fop = new FileOp;
 
   fop->type = type;
   fop->format = NULL;
   fop->format_data = NULL;
+  fop->context = context;
   fop->document = NULL;
 
   fop->mutex = new base::mutex();
diff --git a/src/app/file/file.h b/src/app/file/file.h
index 463776467..d29d2b71f 100644
--- a/src/app/file/file.h
+++ b/src/app/file/file.h
@@ -46,6 +46,7 @@ namespace raster {
 }
 
 namespace app {
+  class Context;
   class Document;
   class FileFormat;
   class FormatOptions;
@@ -70,6 +71,7 @@ namespace app {
     FileOpType type;              // Operation type: 0=load, 1=save.
     FileFormat* format;
     void* format_data;            // Custom data for the FileFormat::onLoad/onSave operations.
+    Context* context;
     Document* document;           // Loaded document, or document to be saved.
     std::string filename;         // File-name to load/save.
 
@@ -119,13 +121,13 @@ namespace app {
 
   // High-level routines to load/save documents.
 
-  Document* load_document(const char* filename);
-  int save_document(Document* document);
+  Document* load_document(Context* context, const char* filename);
+  int save_document(Context* context, Document* document);
 
   // Low-level routines to load/save documents.
 
-  FileOp* fop_to_load_document(const char* filename, int flags);
-  FileOp* fop_to_save_document(Document* document);
+  FileOp* fop_to_load_document(Context* context, const char* filename, int flags);
+  FileOp* fop_to_save_document(Context* context, Document* document);
   void fop_operate(FileOp* fop, IFileOpProgress* progress);
   void fop_done(FileOp* fop);
   void fop_stop(FileOp* fop);
diff --git a/src/app/file/file_tests.cpp b/src/app/file/file_tests.cpp
index 8aa0769de..3362c5242 100644
--- a/src/app/file/file_tests.cpp
+++ b/src/app/file/file_tests.cpp
@@ -19,6 +19,7 @@
 #include "tests/test.h"
 
 #include "app/app.h"
+#include "app/context.h"
 #include "app/document.h"
 #include "app/file/file.h"
 #include "app/file/file_formats_manager.h"
@@ -37,6 +38,7 @@ TEST(File, SeveralSizes)
   // Register all possible image formats.
   FileFormatsManager::instance().registerAllFormats();
   std::vector<char> fn(256);
+  app::Context context;
 
   for (int w=10; w<=10+503*2; w+=503) {
     for (int h=10; h<=10+503*2; h+=503) {
@@ -61,11 +63,11 @@ TEST(File, SeveralSizes)
           }
         }
 
-        save_document(doc);
+        save_document(&context, doc);
       }
 
       {
-        base::UniquePtr<Document> doc(load_document(&fn[0]));
+        base::UniquePtr<Document> doc(load_document(&context, &fn[0]));
         ASSERT_EQ(w, doc->getSprite()->getWidth());
         ASSERT_EQ(h, doc->getSprite()->getHeight());
 
diff --git a/src/app/file/gif_format.cpp b/src/app/file/gif_format.cpp
index 606273941..e603d3cd0 100644
--- a/src/app/file/gif_format.cpp
+++ b/src/app/file/gif_format.cpp
@@ -1,5 +1,5 @@
 /* Aseprite
- * Copyright (C) 2001-2013  David Capello
+ * Copyright (C) 2001-2014  David Capello
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -20,16 +20,23 @@
 #include "config.h"
 #endif
 
+#include "app/console.h"
+#include "app/context.h"
 #include "app/document.h"
 #include "app/file/file.h"
 #include "app/file/file_format.h"
 #include "app/file/format_options.h"
+#include "app/file/gif_options.h"
+#include "app/ini_file.h"
 #include "app/modules/gui.h"
 #include "app/util/autocrop.h"
 #include "base/file_handle.h"
 #include "base/unique_ptr.h"
 #include "raster/raster.h"
 #include "ui/alert.h"
+#include "ui/button.h"
+
+#include "generated_gif_options.h"
 
 #include <gif_lib.h>
 
@@ -72,6 +79,7 @@ struct GifData
 };
 
 class GifFormat : public FileFormat {
+
   const char* onGetName() const { return "gif"; }
   const char* onGetExtensions() const { return "gif"; }
   int onGetFlags() const {
@@ -84,7 +92,8 @@ class GifFormat : public FileFormat {
       FILE_SUPPORT_GRAYA |
       FILE_SUPPORT_INDEXED |
       FILE_SUPPORT_FRAMES |
-      FILE_SUPPORT_PALETTES;
+      FILE_SUPPORT_PALETTES |
+      FILE_SUPPORT_GET_FORMAT_OPTIONS;
   }
 
   bool onLoad(FileOp* fop);
@@ -93,6 +102,7 @@ class GifFormat : public FileFormat {
 #ifdef ENABLE_SAVE
   bool onSave(FileOp* fop) OVERRIDE;
 #endif
+  SharedPtr<FormatOptions> onGetFormatOptions(FileOp* fop) OVERRIDE;
 };
 
 FileFormat* CreateGifFormat()
@@ -157,7 +167,8 @@ bool GifFormat::onLoad(FileOp* fop)
     ColorMapObject* colormap = gif_file->SColorMap;
     for (int i=0; i<colormap->ColorCount; ++i) {
       current_palette->setEntry(i,
-        rgba(colormap->Colors[i].Red,
+        rgba(
+          colormap->Colors[i].Red,
           colormap->Colors[i].Green,
           colormap->Colors[i].Blue, 255));
     }
@@ -208,9 +219,11 @@ bool GifFormat::onLoad(FileOp* fop)
         if (gif_file->Image.ColorMap) {
           ColorMapObject* colormap = gif_file->Image.ColorMap;
           for (int i=0; i<colormap->ColorCount; ++i) {
-            current_palette->setEntry(i, rgba(colormap->Colors[i].Red,
-                                               colormap->Colors[i].Green,
-                                               colormap->Colors[i].Blue, 255));
+            current_palette->setEntry(i,
+              rgba(
+                colormap->Colors[i].Red,
+                colormap->Colors[i].Green,
+                colormap->Colors[i].Blue, 255));
           }
         }
 
@@ -249,7 +262,7 @@ bool GifFormat::onLoad(FileOp* fop)
         data->frames[frame_num].disposal_method = disposal_method;
         data->frames[frame_num].mask_index = transparent_index;
 
-        PRINTF("Frame[%d] transparent index  = %d\n", (int)frame_num, transparent_index);
+        // PRINTF("Frame[%d] transparent index  = %d\n", (int)frame_num, transparent_index);
 
         ++frame_num;
 
@@ -272,8 +285,8 @@ bool GifFormat::onLoad(FileOp* fop)
             transparent_index = (extension[1] & 1) ? extension[4]: -1;
             frame_delay       = (extension[3] << 8) | extension[2];
 
-            TRACE("Disposal method: %d\nTransparent index: %d\nFrame delay: %d\n",
-                  disposal_method, transparent_index, frame_delay);
+            // PRINTF("Disposal method: %d\nTransparent index: %d\nFrame delay: %d\n",
+            //   disposal_method, transparent_index, frame_delay);
           }
         }
 
@@ -355,7 +368,7 @@ bool GifFormat::onPostLoad(FileOp* fop)
       ui::Alert::show("GIF Conversion"
                       "<<The selected file: %s"
                       "<<is a transparent GIF image which uses multiple background colors."
-                      "<<ASEPRITE cannot handle this kind of GIF correctly in Indexed format."
+                      "<<" PACKAGE " cannot handle this kind of GIF correctly in Indexed format."
                       "<<What would you like to do?"
                       "||Convert to &RGBA||Keep &Indexed||&Cancel",
                       fop->document->getFilename().c_str());
@@ -367,6 +380,7 @@ bool GifFormat::onPostLoad(FileOp* fop)
   }
 
   // Create the sprite with the GIF dimension
+  // TODO instead of 256 use the number of colors from the document
   UniquePtr<Sprite> sprite(new Sprite(pixelFormat, data->sprite_w, data->sprite_h, 256));
 
   // Create the main layer
@@ -524,26 +538,58 @@ bool GifFormat::onSave(FileOp* fop)
   if (!gif_file)
     throw Exception("Error creating GIF file.\n");
 
+  SharedPtr<GifOptions> gif_options = fop->seq.format_options;
   Sprite* sprite = fop->document->getSprite();
   int sprite_w = sprite->getWidth();
   int sprite_h = sprite->getHeight();
   PixelFormat sprite_format = sprite->getPixelFormat();
-  bool interlace = false;
+  bool interlaced = gif_options->interlaced();
   int loop = 0;
+  bool has_background = (sprite->getBackgroundLayer() ? true: false);
   int background_color = (sprite_format == IMAGE_INDEXED ? sprite->getTransparentColor(): 0);
-  int transparent_index = (sprite->getBackgroundLayer() ? -1: sprite->getTransparentColor());
+  int transparent_index = (has_background ? -1: sprite->getTransparentColor());
 
-  Palette* current_palette = sprite->getPalette(FrameNumber(0));
-  Palette* previous_palette = current_palette;
-  ColorMapObject* color_map = GifMakeMapObject(current_palette->size(), NULL);
-  for (int i = 0; i < current_palette->size(); ++i) {
-    color_map->Colors[i].Red   = rgba_getr(current_palette->getEntry(i));
-    color_map->Colors[i].Green = rgba_getg(current_palette->getEntry(i));
-    color_map->Colors[i].Blue  = rgba_getb(current_palette->getEntry(i));
+  Palette current_palette = *sprite->getPalette(FrameNumber(0));
+  Palette previous_palette(current_palette);
+  RgbMap rgbmap;
+
+  // The color map must be a power of two.
+  int color_map_size = current_palette.size();
+  for (int i = 30; i >= 0; --i) {
+    if (color_map_size & (1 << i)) {
+      color_map_size = (1 << (i + (color_map_size & (1 << (i - 1)) ? 1: 0)));
+      break;
+    }
   }
+  ASSERT(color_map_size > 0 && color_map_size <= 256);
 
-  if (EGifPutScreenDesc(gif_file, sprite_w, sprite_h,
-                        color_map->BitsPerPixel,
+  ColorMapObject* color_map = NULL;
+  int bpp;
+
+  // We use a global color map only if this is a transparent GIF
+  if (!has_background) {
+    color_map = GifMakeMapObject(color_map_size, NULL);
+    if (color_map == NULL)
+      throw std::bad_alloc();
+
+    int i;
+    for (i = 0; i < current_palette.size(); ++i) {
+      color_map->Colors[i].Red   = rgba_getr(current_palette.getEntry(i));
+      color_map->Colors[i].Green = rgba_getg(current_palette.getEntry(i));
+      color_map->Colors[i].Blue  = rgba_getb(current_palette.getEntry(i));
+    }
+    for (; i < color_map_size; ++i) {
+      color_map->Colors[i].Red   = 0;
+      color_map->Colors[i].Green = 0;
+      color_map->Colors[i].Blue  = 0;
+    }
+
+    bpp = color_map->BitsPerPixel;
+  }
+  else
+    bpp = 8;
+
+  if (EGifPutScreenDesc(gif_file, sprite_w, sprite_h, bpp,
                         background_color, color_map) == GIF_ERROR)
     throw Exception("Error writing GIF header.\n");
 
@@ -562,44 +608,40 @@ bool GifFormat::onSave(FileOp* fop)
   clear_image(current_image, background_color);
   clear_image(previous_image, background_color);
 
-  for (FrameNumber frame_num(0); frame_num<sprite->getTotalFrames(); ++frame_num) {
-    current_palette = sprite->getPalette(frame_num);
+  ColorMapObject* image_color_map = NULL;
 
+  for (FrameNumber frame_num(0); frame_num<sprite->getTotalFrames(); ++frame_num) {
     // If the sprite is RGB or Grayscale, we must to convert it to Indexed on the fly.
     if (sprite_format != IMAGE_INDEXED) {
-      clear_image(buffer_image, 0);
+      clear_image(buffer_image, background_color);
       layer_render(sprite->getFolder(), buffer_image, 0, 0, frame_num);
 
-      switch (sprite_format) {
-
-        // Convert the RGB image to Indexed
-        case IMAGE_RGB:
-          for (int y = 0; y < sprite_h; ++y)
-            for (int x = 0; x < sprite_w; ++x) {
-              uint32_t pixel_value = get_pixel_fast<RgbTraits>(buffer_image, x, y);
-              put_pixel_fast<IndexedTraits>(current_image, x, y,
-                                            (rgba_geta(pixel_value) >= 128) ?
-                                            current_palette->findBestfit(rgba_getr(pixel_value),
-                                                                         rgba_getg(pixel_value),
-                                                                         rgba_getb(pixel_value)):
-                                            transparent_index);
-            }
+      switch (gif_options->quantize()) {
+        case GifOptions::NoQuantize:
+          sprite->getPalette(frame_num)->copyColorsTo(&current_palette);
           break;
+        case GifOptions::QuantizeEach:
+        case GifOptions::QuantizeAll:
+          {
+            current_palette.makeBlack();
 
-        // Convert the Grayscale image to Indexed
-        case IMAGE_GRAYSCALE:
-          for (int y = 0; y < sprite_h; ++y)
-            for (int x = 0; x < sprite_w; ++x) {
-              uint16_t pixel_value = get_pixel_fast<GrayscaleTraits>(buffer_image, x, y);
-              put_pixel_fast<IndexedTraits>(current_image, x, y,
-                                            (graya_geta(pixel_value) >= 128) ?
-                                            current_palette->findBestfit(graya_getv(pixel_value),
-                                                                         graya_getv(pixel_value),
-                                                                         graya_getv(pixel_value)):
-                                            transparent_index);
-            }
+            std::vector<Image*> imgarray(1);
+            imgarray[0] = buffer_image;
+            raster::quantization::create_palette_from_images(imgarray, &current_palette, has_background);
+          }
           break;
       }
+
+      rgbmap.regenerate(&current_palette, transparent_index);
+
+      quantization::convert_pixel_format(
+        buffer_image,
+        current_image,
+        IMAGE_INDEXED,
+        gif_options->dithering(),
+        &rgbmap,
+        &current_palette,
+        has_background);
     }
     // If the sprite is Indexed, we can render directly into "current_image".
     else {
@@ -679,26 +721,32 @@ bool GifFormat::onSave(FileOp* fop)
     }
 
     // Image color map
-    ColorMapObject* image_color_map = NULL;
-    if (current_palette != previous_palette) {
-      image_color_map = GifMakeMapObject(current_palette->size(), NULL);
-      for (int i = 0; i < current_palette->size(); ++i) {
-        image_color_map->Colors[i].Red   = rgba_getr(current_palette->getEntry(i));
-        image_color_map->Colors[i].Green = rgba_getg(current_palette->getEntry(i));
-        image_color_map->Colors[i].Blue  = rgba_getb(current_palette->getEntry(i));
+    if ((!color_map && frame_num == 0) ||
+        (current_palette.countDiff(&previous_palette, NULL, NULL) > 0)) {
+      if (!image_color_map) {
+        image_color_map = GifMakeMapObject(current_palette.size(), NULL);
+        if (image_color_map == NULL)
+          throw std::bad_alloc();
       }
-      previous_palette = current_palette;
+
+      for (int i = 0; i < current_palette.size(); ++i) {
+        image_color_map->Colors[i].Red   = rgba_getr(current_palette.getEntry(i));
+        image_color_map->Colors[i].Green = rgba_getg(current_palette.getEntry(i));
+        image_color_map->Colors[i].Blue  = rgba_getb(current_palette.getEntry(i));
+      }
+
+      current_palette.copyColorsTo(&previous_palette);
     }
 
     // Write the image record.
     if (EGifPutImageDesc(gif_file,
                          frame_x, frame_y,
-                         frame_w, frame_h, interlace ? 1: 0,
+                         frame_w, frame_h, interlaced ? 1: 0,
                          image_color_map) == GIF_ERROR)
       throw Exception("Error writing GIF frame %d.\n", (int)frame_num);
 
     // Write the image data (pixels).
-    if (interlace) {
+    if (interlaced) {
       // Need to perform 4 passes on the images.
       for (int i=0; i<4; ++i)
         for (int y = interlaced_offset[i]; y < frame_h; y += interlaced_jumps[i]) {
@@ -711,7 +759,7 @@ bool GifFormat::onSave(FileOp* fop)
     }
     else {
       // Write all image scanlines (not interlaced in this case).
-      for (int y = 0; y < frame_h; ++y) {
+      for (int y=0; y<frame_h; ++y) {
         IndexedTraits::address_t addr =
           (IndexedTraits::address_t)current_image->getPixelAddress(frame_x, frame_y + y);
 
@@ -727,4 +775,69 @@ bool GifFormat::onSave(FileOp* fop)
 }
 #endif
 
+SharedPtr<FormatOptions> GifFormat::onGetFormatOptions(FileOp* fop)
+{
+  SharedPtr<GifOptions> gif_options;
+  if (fop->document->getFormatOptions() != NULL)
+    gif_options = SharedPtr<GifOptions>(fop->document->getFormatOptions());
+
+  if (!gif_options)
+    gif_options.reset(new GifOptions);
+
+  // Non-interactive mode
+  if (!fop->context->isUiAvailable())
+    return gif_options;
+
+  try {
+    // Configuration parameters
+    gif_options->setQuantize((GifOptions::Quantize)get_config_int("GIF", "Quantize", (int)gif_options->quantize()));
+    gif_options->setInterlaced(get_config_bool("GIF", "Interlaced", gif_options->interlaced()));
+    gif_options->setDithering((raster::DitheringMethod)get_config_int("GIF", "Dither", (int)gif_options->dithering()));
+
+    // Load the window to ask to the user the GIF options he wants.
+
+    app::gen::GifOptions win;
+    win.rgbOptions()->setVisible(fop->document->getSprite()->getPixelFormat() != IMAGE_INDEXED);
+
+    switch (gif_options->quantize()) {
+      case GifOptions::NoQuantize: win.noQuantize()->setSelected(true); break;
+      case GifOptions::QuantizeEach: win.quantizeEach()->setSelected(true); break;
+      case GifOptions::QuantizeAll: win.quantizeAll()->setSelected(true); break;
+    }
+    win.interlaced()->setSelected(gif_options->interlaced());
+
+    win.dither()->setEnabled(true);
+    win.dither()->setSelected(gif_options->dithering() == raster::DITHERING_ORDERED);
+
+    win.openWindowInForeground();
+
+    if (win.getKiller() == win.ok()) {
+      if (win.quantizeAll()->isSelected())
+        gif_options->setQuantize(GifOptions::QuantizeAll);
+      else if (win.quantizeEach()->isSelected())
+        gif_options->setQuantize(GifOptions::QuantizeEach);
+      else if (win.noQuantize()->isSelected())
+        gif_options->setQuantize(GifOptions::NoQuantize);
+
+      gif_options->setInterlaced(win.interlaced()->isSelected());
+      gif_options->setDithering(win.dither()->isSelected() ?
+        raster::DITHERING_ORDERED:
+        raster::DITHERING_NONE);
+
+      set_config_int("GIF", "Quantize", gif_options->quantize());
+      set_config_bool("GIF", "Interlaced", gif_options->interlaced());
+      set_config_int("GIF", "Dither", gif_options->dithering());
+    }
+    else {
+      gif_options.reset(NULL);
+    }
+
+    return gif_options;
+  }
+  catch (std::exception& e) {
+    Console::showException(e);
+    return SharedPtr<GifOptions>(0);
+  }
+}
+
 } // namespace app
diff --git a/src/app/file/gif_options.h b/src/app/file/gif_options.h
new file mode 100644
index 000000000..ba723934b
--- /dev/null
+++ b/src/app/file/gif_options.h
@@ -0,0 +1,58 @@
+/* Aseprite
+ * Copyright (C) 2001-2014  David Capello
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef APP_FILE_GIF_OPTIONS_H_INCLUDED
+#define APP_FILE_GIF_OPTIONS_H_INCLUDED
+#pragma once
+
+#include "app/file/format_options.h"
+#include "raster/dithering_method.h"
+
+namespace app {
+
+  // Data for GIF files
+  class GifOptions : public FormatOptions {
+  public:
+    enum Quantize { NoQuantize, QuantizeEach, QuantizeAll };
+
+    GifOptions(
+      Quantize quantize = QuantizeEach,
+      bool interlaced = false,
+      DitheringMethod dithering = raster::DITHERING_NONE)
+      : m_quantize(quantize)
+      , m_interlaced(interlaced)
+      , m_dithering(dithering) {
+    }
+
+    Quantize quantize() const { return m_quantize; }
+    bool interlaced() const { return m_interlaced; }
+    raster::DitheringMethod dithering() const { return m_dithering; }
+
+    void setQuantize(const Quantize quantize) { m_quantize = quantize; }
+    void setInterlaced(bool interlaced) { m_interlaced = interlaced; }
+    void setDithering(const raster::DitheringMethod dithering) { m_dithering = dithering; }
+
+  private:
+    Quantize m_quantize;
+    bool m_interlaced;
+    raster::DitheringMethod m_dithering;
+  };
+
+} // namespace app
+
+#endif
diff --git a/src/app/file/gif_tests.cpp b/src/app/file/gif_tests.cpp
new file mode 100644
index 000000000..5277e636b
--- /dev/null
+++ b/src/app/file/gif_tests.cpp
@@ -0,0 +1,312 @@
+/* Aseprite
+ * Copyright (C) 2014  David Capello
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "tests/test.h"
+
+#include "app/context.h"
+#include "app/document.h"
+#include "app/file/file.h"
+#include "app/file/file_formats_manager.h"
+#include "app/file/gif_options.h"
+#include "raster/raster.h"
+#include "she/scoped_handle.h"
+#include "she/system.h"
+
+using namespace app;
+
+typedef base::UniquePtr<Document> DocumentPtr;
+
+class GifFormat : public ::testing::Test {
+public:
+  GifFormat() : m_system(she::create_system()) {
+    FileFormatsManager::instance().registerAllFormats();
+  }
+
+protected:
+  app::Context m_context;
+  she::ScopedHandle<she::System> m_system;
+};
+
+TEST_F(GifFormat, Dimensions)
+{
+  const char* fn = "test.gif";
+
+  {
+    DocumentPtr doc(Document::createBasicDocument(IMAGE_INDEXED, 31, 29, 14));
+    Sprite* sprite = doc->getSprite();
+    doc->setFilename(fn);
+    sprite->setTransparentColor(3);
+
+    LayerImage* layer = dynamic_cast<LayerImage*>(sprite->getFolder()->getFirstLayer());
+    ASSERT_NE((LayerImage*)NULL, layer);
+
+    Image* image = sprite->getStock()->getImage(layer->getCel(FrameNumber(0))->getImage());
+    clear_image(image, doc->getSprite()->getTransparentColor());
+
+    save_document(&m_context, doc);
+  }
+
+  {
+    DocumentPtr doc(load_document(&m_context, fn));
+    Sprite* sprite = doc->getSprite();
+
+    EXPECT_EQ(31, sprite->getWidth());
+    EXPECT_EQ(29, sprite->getHeight());
+    EXPECT_EQ(3, sprite->getTransparentColor());
+    // TODO instead of 256, this should be 16 as Gif files contains
+    // palettes that are power of two.
+    EXPECT_EQ(256, sprite->getPalette(FrameNumber(0))->size());
+  }
+}
+
+TEST_F(GifFormat, OpaqueIndexed)
+{
+  const char* fn = "test.gif";
+
+  {
+    DocumentPtr doc(Document::createBasicDocument(IMAGE_INDEXED, 2, 2, 4));
+    Sprite* sprite = doc->getSprite();
+    doc->setFilename(fn);
+
+    Palette* pal = sprite->getPalette(FrameNumber(0));
+    pal->setEntry(0, rgb(255, 255, 255));
+    pal->setEntry(1, rgb(255, 13, 254));
+    pal->setEntry(2, rgb(129, 255, 32));
+    pal->setEntry(3, rgb(0, 0, 255));
+
+    LayerImage* layer = dynamic_cast<LayerImage*>(sprite->getFolder()->getFirstLayer());
+    layer->setBackground(true);
+    ASSERT_NE((LayerImage*)NULL, layer);
+
+    Image* image = sprite->getStock()->getImage(layer->getCel(FrameNumber(0))->getImage());
+    image->putPixel(0, 0, 0);
+    image->putPixel(0, 1, 1);
+    image->putPixel(1, 0, 2);
+    image->putPixel(1, 1, 3);
+
+    save_document(&m_context, doc);
+  }
+
+  {
+    DocumentPtr doc(load_document(&m_context, fn));
+    Sprite* sprite = doc->getSprite();
+
+    LayerImage* layer = dynamic_cast<LayerImage*>(sprite->getFolder()->getFirstLayer());
+    ASSERT_NE((LayerImage*)NULL, layer);
+    EXPECT_TRUE(layer->isBackground());
+
+    Palette* pal = sprite->getPalette(FrameNumber(0));
+    EXPECT_EQ(rgb(255, 255, 255), pal->getEntry(0));
+    EXPECT_EQ(rgb(255, 13, 254), pal->getEntry(1));
+    EXPECT_EQ(rgb(129, 255, 32), pal->getEntry(2));
+    EXPECT_EQ(rgb(0, 0, 255), pal->getEntry(3));
+
+    Image* image = sprite->getStock()->getImage(layer->getCel(FrameNumber(0))->getImage());
+    EXPECT_EQ(0, sprite->getTransparentColor());
+    EXPECT_EQ(0, image->getPixel(0, 0));
+    EXPECT_EQ(1, image->getPixel(0, 1));
+    EXPECT_EQ(2, image->getPixel(1, 0));
+    EXPECT_EQ(3, image->getPixel(1, 1));
+  }
+}
+
+TEST_F(GifFormat, TransparentIndexed)
+{
+  const char* fn = "test.gif";
+
+  {
+    DocumentPtr doc(Document::createBasicDocument(IMAGE_INDEXED, 2, 2, 4));
+    Sprite* sprite = doc->getSprite();
+    doc->setFilename(fn);
+
+    Palette* pal = sprite->getPalette(FrameNumber(0));
+    pal->setEntry(0, rgb(255, 255, 255));
+    pal->setEntry(1, rgb(255, 13, 254));
+    pal->setEntry(2, rgb(129, 255, 32));
+    pal->setEntry(3, rgb(0, 0, 255));
+
+    LayerImage* layer = dynamic_cast<LayerImage*>(sprite->getFolder()->getFirstLayer());
+    ASSERT_NE((LayerImage*)NULL, layer);
+
+    Image* image = sprite->getStock()->getImage(layer->getCel(FrameNumber(0))->getImage());
+    image->putPixel(0, 0, 0);
+    image->putPixel(0, 1, 1);
+    image->putPixel(1, 0, 2);
+    image->putPixel(1, 1, 3);
+
+    save_document(&m_context, doc);
+  }
+
+  {
+    DocumentPtr doc(load_document(&m_context, fn));
+    Sprite* sprite = doc->getSprite();
+
+    LayerImage* layer = dynamic_cast<LayerImage*>(sprite->getFolder()->getFirstLayer());
+    ASSERT_NE((LayerImage*)NULL, layer);
+    EXPECT_FALSE(layer->isBackground());
+
+    Palette* pal = sprite->getPalette(FrameNumber(0));
+    EXPECT_EQ(rgb(255, 255, 255), pal->getEntry(0));
+    EXPECT_EQ(rgb(255, 13, 254), pal->getEntry(1));
+    EXPECT_EQ(rgb(129, 255, 32), pal->getEntry(2));
+    EXPECT_EQ(rgb(0, 0, 255), pal->getEntry(3));
+
+    Image* image = sprite->getStock()->getImage(layer->getCel(FrameNumber(0))->getImage());
+    EXPECT_EQ(0, sprite->getTransparentColor());
+    EXPECT_EQ(0, image->getPixel(0, 0));
+    EXPECT_EQ(1, image->getPixel(0, 1));
+    EXPECT_EQ(2, image->getPixel(1, 0));
+    EXPECT_EQ(3, image->getPixel(1, 1));
+  }
+}
+
+TEST_F(GifFormat, TransparentRgbQuantization)
+{
+  const char* fn = "test.gif";
+
+  {
+    DocumentPtr doc(Document::createBasicDocument(IMAGE_RGB, 2, 2, 256));
+    Sprite* sprite = doc->getSprite();
+    doc->setFilename(fn);
+
+    LayerImage* layer = dynamic_cast<LayerImage*>(sprite->getFolder()->getFirstLayer());
+    ASSERT_NE((LayerImage*)NULL, layer);
+
+    Image* image = sprite->getStock()->getImage(layer->getCel(FrameNumber(0))->getImage());
+    image->putPixel(0, 0, rgba(0, 0, 0, 0));
+    image->putPixel(0, 1, rgb(255, 0, 0));
+    image->putPixel(1, 0, rgb(0, 255, 0));
+    image->putPixel(1, 1, rgb(0, 0, 255));
+
+    save_document(&m_context, doc);
+  }
+
+  {
+    DocumentPtr doc(load_document(&m_context, fn));
+    Sprite* sprite = doc->getSprite();
+
+    LayerImage* layer = dynamic_cast<LayerImage*>(sprite->getFolder()->getFirstLayer());
+    ASSERT_NE((LayerImage*)NULL, layer);
+
+    Palette* pal = sprite->getPalette(FrameNumber(0));
+    Image* image = sprite->getStock()->getImage(layer->getCel(FrameNumber(0))->getImage());
+    EXPECT_EQ(0, sprite->getTransparentColor());
+    EXPECT_EQ(0, image->getPixel(0, 0));
+    EXPECT_EQ(rgb(255, 0, 0), pal->getEntry(image->getPixel(0, 1)));
+    EXPECT_EQ(rgb(0, 255, 0), pal->getEntry(image->getPixel(1, 0)));
+    EXPECT_EQ(rgb(0, 0, 255), pal->getEntry(image->getPixel(1, 1)));
+  }
+}
+
+TEST_F(GifFormat, OpaqueRgbQuantization)
+{
+  const char* fn = "test.gif";
+
+  {
+    DocumentPtr doc(Document::createBasicDocument(IMAGE_RGB, 2, 2, 256));
+    Sprite* sprite = doc->getSprite();
+    doc->setFilename(fn);
+
+    LayerImage* layer = dynamic_cast<LayerImage*>(sprite->getFolder()->getFirstLayer());
+    layer->setBackground(true);
+    ASSERT_NE((LayerImage*)NULL, layer);
+    EXPECT_NE((LayerImage*)NULL, sprite->getBackgroundLayer());
+
+    Image* image = sprite->getStock()->getImage(layer->getCel(FrameNumber(0))->getImage());
+    image->putPixel(0, 0, rgb(0, 0, 0));
+    image->putPixel(0, 1, rgb(255, 0, 0));
+    image->putPixel(1, 0, rgb(0, 255, 0));
+    image->putPixel(1, 1, rgb(0, 0, 255));
+
+    save_document(&m_context, doc);
+  }
+
+  {
+    DocumentPtr doc(load_document(&m_context, fn));
+    Sprite* sprite = doc->getSprite();
+
+    LayerImage* layer = dynamic_cast<LayerImage*>(sprite->getFolder()->getFirstLayer());
+    ASSERT_NE((LayerImage*)NULL, layer);
+    EXPECT_TRUE(layer->isBackground());
+    EXPECT_EQ(layer, sprite->getBackgroundLayer());
+
+    Palette* pal = sprite->getPalette(FrameNumber(0));
+    Image* image = sprite->getStock()->getImage(layer->getCel(FrameNumber(0))->getImage());
+    EXPECT_EQ(0, sprite->getTransparentColor());
+    EXPECT_EQ(rgb(0, 0, 0), pal->getEntry(image->getPixel(0, 0)));
+    EXPECT_EQ(rgb(255, 0, 0), pal->getEntry(image->getPixel(0, 1)));
+    EXPECT_EQ(rgb(0, 255, 0), pal->getEntry(image->getPixel(1, 0)));
+    EXPECT_EQ(rgb(0, 0, 255), pal->getEntry(image->getPixel(1, 1)));
+  }
+}
+
+TEST_F(GifFormat, OpaqueRgbQuantizationTwoLayers)
+{
+  const char* fn = "test.gif";
+
+  {
+    DocumentPtr doc(Document::createBasicDocument(IMAGE_RGB, 2, 2, 256));
+    Sprite* sprite = doc->getSprite();
+    doc->setFilename(fn);
+
+    LayerImage* layer1 = dynamic_cast<LayerImage*>(sprite->getFolder()->getFirstLayer());
+    layer1->setBackground(true);
+
+    LayerImage* layer2 = new LayerImage(sprite);
+    sprite->getFolder()->addLayer(layer2);
+
+    Image* image1 = sprite->getStock()->getImage(layer1->getCel(FrameNumber(0))->getImage());
+    Image* image2 = Image::create(IMAGE_RGB, 2, 2);
+    int image2Idx = sprite->getStock()->addImage(image2);
+    Cel* cel2 = new Cel(FrameNumber(0), image2Idx);
+    layer2->addCel(cel2);
+
+    image1->clear(rgba(255, 255, 255, 255));
+    image2->putPixel(0, 0, rgba(255, 0, 0, 255));
+    image2->putPixel(1, 1, rgba(196, 0, 0, 255));
+
+    Palette* pal = sprite->getPalette(FrameNumber(0));
+    pal->setEntry(0, rgba(255, 255, 255, 255));
+    pal->setEntry(1, rgba(255, 0, 0, 255));
+
+    // Do not modify palettes
+    doc->setFormatOptions(SharedPtr<FormatOptions>(new GifOptions(GifOptions::NoQuantize)));
+    save_document(&m_context, doc);
+  }
+
+  {
+    DocumentPtr doc(load_document(&m_context, fn));
+    Sprite* sprite = doc->getSprite();
+
+    LayerImage* layer = dynamic_cast<LayerImage*>(sprite->getFolder()->getFirstLayer());
+    ASSERT_NE((LayerImage*)NULL, layer);
+    ASSERT_TRUE(layer->isBackground());
+
+    Palette* pal = sprite->getPalette(FrameNumber(0));
+    Image* image = sprite->getStock()->getImage(layer->getCel(FrameNumber(0))->getImage());
+    EXPECT_EQ(0, sprite->getTransparentColor());
+
+    EXPECT_EQ(1, image->getPixel(0, 0));
+    EXPECT_EQ(0, image->getPixel(0, 1));
+    EXPECT_EQ(0, image->getPixel(1, 0));
+    EXPECT_EQ(1, image->getPixel(1, 1));
+
+    EXPECT_EQ(rgba(255, 255, 255, 255), pal->getEntry(0));
+    EXPECT_EQ(rgba(255, 0, 0, 255), pal->getEntry(1));
+  }
+}
diff --git a/src/app/file/jpeg_format.cpp b/src/app/file/jpeg_format.cpp
index e4e39a8a8..aaf57001d 100644
--- a/src/app/file/jpeg_format.cpp
+++ b/src/app/file/jpeg_format.cpp
@@ -22,6 +22,8 @@
 
 #include "app/app.h"
 #include "app/console.h"
+#include "app/context.h"
+#include "app/document.h"
 #include "app/file/file.h"
 #include "app/file/file_format.h"
 #include "app/file/format_options.h"
@@ -358,15 +360,21 @@ bool JpegFormat::onSave(FileOp* fop)
 // Shows the JPEG configuration dialog.
 SharedPtr<FormatOptions> JpegFormat::onGetFormatOptions(FileOp* fop)
 {
-  SharedPtr<JpegOptions> jpeg_options(new JpegOptions());
+  SharedPtr<JpegOptions> jpeg_options;
+  if (fop->document->getFormatOptions() != NULL)
+    jpeg_options = SharedPtr<JpegOptions>(fop->document->getFormatOptions());
+
+  if (!jpeg_options)
+    jpeg_options.reset(new JpegOptions);
+
+  // Non-interactive mode
+  if (!fop->context->isUiAvailable())
+    return jpeg_options;
+
   try {
     // Configuration parameters
     jpeg_options->quality = get_config_float("JPEG", "Quality", 1.0f);
 
-    // Interactive mode
-    if (!App::instance()->isGui())
-      return jpeg_options;
-
     // Load the window to ask to the user the JPEG options he wants.
     UniquePtr<ui::Window> window(app::load_widget<ui::Window>("jpeg_options.xml", "jpeg_options"));
     ui::Slider* slider_quality = app::find_widget<ui::Slider>(window, "quality");
diff --git a/src/app/thumbnail_generator.cpp b/src/app/thumbnail_generator.cpp
index 1f156a185..30aa190d1 100644
--- a/src/app/thumbnail_generator.cpp
+++ b/src/app/thumbnail_generator.cpp
@@ -23,6 +23,7 @@
 #include "app/thumbnail_generator.h"
 
 #include "app/app.h"
+#include "app/context.h"
 #include "app/document.h"
 #include "app/file/file.h"
 #include "app/file_system.h"
@@ -190,9 +191,12 @@ void ThumbnailGenerator::addWorkerToGenerateThumbnail(IFileItem* fileitem)
       getWorkerStatus(fileitem, progress) != WithoutWorker)
     return;
 
-  FileOp* fop = fop_to_load_document(fileitem->getFileName().c_str(),
-                                     FILE_LOAD_SEQUENCE_NONE |
-                                     FILE_LOAD_ONE_FRAME);
+  Context tmpContext;
+  FileOp* fop = fop_to_load_document(&tmpContext,
+    fileitem->getFileName().c_str(),
+    FILE_LOAD_SEQUENCE_NONE |
+    FILE_LOAD_ONE_FRAME);
+
   if (!fop)
     return;
 
diff --git a/src/app/util/clipboard.cpp b/src/app/util/clipboard.cpp
index 13231a09d..64cc1bb46 100644
--- a/src/app/util/clipboard.cpp
+++ b/src/app/util/clipboard.cpp
@@ -204,7 +204,7 @@ void clipboard::paste()
     RgbMap* dst_rgbmap = dst_sprite->getRgbMap(editor->getFrame());
 
     src_image = quantization::convert_pixel_format(
-      clipboard_image, dst_sprite->getPixelFormat(),
+      clipboard_image, NULL, dst_sprite->getPixelFormat(),
       DITHERING_NONE, dst_rgbmap, clipboard_palette,
       false);
   }
diff --git a/src/raster/color.h b/src/raster/color.h
index 085581136..0200827c5 100644
--- a/src/raster/color.h
+++ b/src/raster/color.h
@@ -63,6 +63,10 @@ namespace raster {
             (a << rgba_a_shift));
   }
 
+  inline uint32_t rgb(uint8_t r, uint8_t g, uint8_t b) {
+    return rgba(0, 0, 0, 255);
+  }
+
   //////////////////////////////////////////////////////////////////////
   // Grayscale
 
@@ -85,6 +89,10 @@ namespace raster {
             (a << graya_a_shift));
   }
 
+  inline uint16_t gray(uint8_t v) {
+    return graya(v, 255);
+  }
+
 } // namespace raster
 
 #endif
diff --git a/src/raster/palette.cpp b/src/raster/palette.cpp
index 633dd81d9..9320fc69e 100644
--- a/src/raster/palette.cpp
+++ b/src/raster/palette.cpp
@@ -46,9 +46,9 @@ Palette::Palette(FrameNumber frame, int ncolors)
 
   m_frame = frame;
   m_colors.resize(ncolors);
-  m_modifications = 0;
 
-  std::fill(m_colors.begin(), m_colors.end(), rgba(0, 0, 0, 255));
+  makeBlack();
+  m_modifications = 0;
 }
 
 Palette::Palette(const Palette& palette)
diff --git a/src/raster/quantization.cpp b/src/raster/quantization.cpp
index 592d3b91f..e28304feb 100644
--- a/src/raster/quantization.cpp
+++ b/src/raster/quantization.cpp
@@ -45,17 +45,22 @@ namespace quantization {
 using namespace gfx;
 
 // Converts a RGB image to indexed with ordered dithering method.
-static Image* ordered_dithering(const Image* src_image,
-                                int offsetx, int offsety,
-                                const RgbMap* rgbmap,
-                                const Palette* palette);
+static Image* ordered_dithering(
+  const Image* src_image,
+  Image* dst_image,
+  int offsetx, int offsety,
+  const RgbMap* rgbmap,
+  const Palette* palette);
 
-static void create_palette_from_bitmaps(const std::vector<Image*>& images, Palette* palette, bool has_background_layer);
-
-Palette* create_palette_from_rgb(const Sprite* sprite, FrameNumber frameNumber)
+Palette* create_palette_from_rgb(
+  const Sprite* sprite,
+  FrameNumber frameNumber,
+  Palette* palette)
 {
+  if (!palette)
+    palette = new Palette(FrameNumber(0), 256);
+
   bool has_background_layer = (sprite->getBackgroundLayer() != NULL);
-  Palette* palette = new Palette(FrameNumber(0), 256);
   Image* flat_image;
 
   ImagesCollector images(sprite->getFolder(), // All layers
@@ -78,27 +83,31 @@ Palette* create_palette_from_rgb(const Sprite* sprite, FrameNumber frameNumber)
   image_array[c++] = flat_image; // The 'flat_image'
 
   // Generate an optimized palette for all images
-  create_palette_from_bitmaps(image_array, palette, has_background_layer);
+  create_palette_from_images(image_array, palette, has_background_layer);
 
   delete flat_image;
   return palette;
 }
 
-Image* convert_pixel_format(const Image* image,
-                            PixelFormat pixelFormat,
-                            DitheringMethod ditheringMethod,
-                            const RgbMap* rgbmap,
-                            const Palette* palette,
-                            bool is_background_layer)
+Image* convert_pixel_format(
+  const Image* image,
+  Image* new_image,
+  PixelFormat pixelFormat,
+  DitheringMethod ditheringMethod,
+  const RgbMap* rgbmap,
+  const Palette* palette,
+  bool is_background)
 {
+  if (!new_image)
+    new_image = Image::create(pixelFormat, image->getWidth(), image->getHeight());
+
   // RGB -> Indexed with ordered dithering
   if (image->getPixelFormat() == IMAGE_RGB &&
       pixelFormat == IMAGE_INDEXED &&
       ditheringMethod == DITHERING_ORDERED) {
-    return ordered_dithering(image, 0, 0, rgbmap, palette);
+    return ordered_dithering(image, new_image, 0, 0, rgbmap, palette);
   }
 
-  Image* new_image = Image::create(pixelFormat, image->getWidth(), image->getHeight());
   color_t c;
   int r, g, b;
 
@@ -223,7 +232,7 @@ Image* convert_pixel_format(const Image* image,
             ASSERT(dst_it != dst_end);
             c = *src_it;
 
-            if (!is_background_layer && c == image->getMaskColor())
+            if (!is_background && c == image->getMaskColor())
               *dst_it = 0;
             else
               *dst_it = rgba(rgba_getr(palette->getEntry(c)),
@@ -243,7 +252,7 @@ Image* convert_pixel_format(const Image* image,
             ASSERT(dst_it != dst_end);
             c = *src_it;
 
-            if (!is_background_layer && c == image->getMaskColor())
+            if (!is_background && c == image->getMaskColor())
               *dst_it = 0;
             else {
               r = rgba_getr(palette->getEntry(c));
@@ -268,7 +277,7 @@ Image* convert_pixel_format(const Image* image,
             ASSERT(dst_it != dst_end);
             c = *src_it;
 
-            if (!is_background_layer && c == image->getMaskColor())
+            if (!is_background && c == image->getMaskColor())
               *dst_it = dstMaskColor;
             else {
               r = rgba_getr(palette->getEntry(c));
@@ -321,13 +330,14 @@ static int pattern[8][8] = {
                                  4 * ((g1)-(g2)) * ((g1)-(g2)) +        \
                                  2 * ((b1)-(b2)) * ((b1)-(b2)))
 
-static Image* ordered_dithering(const Image* src_image,
-                                int offsetx, int offsety,
-                                const RgbMap* rgbmap,
-                                const Palette* palette)
+static Image* ordered_dithering(
+  const Image* src_image,
+  Image* dst_image,
+  int offsetx, int offsety,
+  const RgbMap* rgbmap,
+  const Palette* palette)
 {
   int oppr, oppg, oppb, oppnrcm;
-  Image *dst_image;
   int dither_const;
   int nr, ng, nb;
   int r, g, b, a;
@@ -335,10 +345,6 @@ static Image* ordered_dithering(const Image* src_image,
   int x, y;
   color_t c;
 
-  dst_image = Image::create(IMAGE_INDEXED, src_image->getWidth(), src_image->getHeight());
-  if (!dst_image)
-    return NULL;
-
   const LockImageBits<RgbTraits> src_bits(src_image);
   LockImageBits<IndexedTraits> dst_bits(dst_image);
   LockImageBits<RgbTraits>::const_iterator src_it = src_bits.begin();
@@ -405,7 +411,7 @@ static Image* ordered_dithering(const Image* src_image,
 // Creation of optimized palette for RGB images
 // by David Capello
 
-static void create_palette_from_bitmaps(const std::vector<Image*>& images, Palette* palette, bool has_background_layer)
+void create_palette_from_images(const std::vector<Image*>& images, Palette* palette, bool has_background_layer)
 {
   quantization::ColorHistogram<5, 6, 5> histogram;
   uint32_t color;
@@ -418,16 +424,45 @@ static void create_palette_from_bitmaps(const std::vector<Image*>& images, Palet
 
   for (int i=0; i<(int)images.size(); ++i) {
     const Image* image = images[i];
-    const LockImageBits<RgbTraits> bits(image);
-    LockImageBits<RgbTraits>::const_iterator it = bits.begin(), end = bits.end();
 
-    for (; it != end; ++it) {
-      color = *it;
+    switch (image->getPixelFormat()) {
+
+      case IMAGE_RGB:
+        {
+          const LockImageBits<RgbTraits> bits(image);
+          LockImageBits<RgbTraits>::const_iterator it = bits.begin(), end = bits.end();
+
+          for (; it != end; ++it) {
+            color = *it;
+
+            if (rgba_geta(color) > 0) {
+              color |= rgba(0, 0, 0, 255);
+              histogram.addSamples(color, 1);
+            }
+          }
+        }
+        break;
+
+      case IMAGE_GRAYSCALE:
+        {
+          const LockImageBits<RgbTraits> bits(image);
+          LockImageBits<RgbTraits>::const_iterator it = bits.begin(), end = bits.end();
+
+          for (; it != end; ++it) {
+            color = *it;
+
+            if (graya_geta(color) > 0) {
+              color = graya_getv(color);
+              histogram.addSamples(rgba(color, color, color, 255), 1);
+            }
+          }
+        }
+        break;
+
+      case IMAGE_INDEXED:
+        ASSERT(false);
+        break;
 
-      if (rgba_geta(color) > 0) {
-        color |= rgba(0, 0, 0, 255);
-        histogram.addSamples(color, 1);
-      }
     }
   }
 
diff --git a/src/raster/quantization.h b/src/raster/quantization.h
index cb28e7bce..0a75055c9 100644
--- a/src/raster/quantization.h
+++ b/src/raster/quantization.h
@@ -24,6 +24,8 @@
 #include "raster/frame_number.h"
 #include "raster/pixel_format.h"
 
+#include <vector>
+
 namespace raster {
 
   class Image;
@@ -34,17 +36,27 @@ namespace raster {
 
   namespace quantization {
 
+    void create_palette_from_images(
+      const std::vector<Image*>& images,
+      Palette* palette,
+      bool has_background_layer);
+
     // Creates a new palette suitable to quantize the given RGB sprite to Indexed color.
-    Palette* create_palette_from_rgb(const Sprite* sprite, FrameNumber frameNumber);
+    Palette* create_palette_from_rgb(
+      const Sprite* sprite,
+      FrameNumber frameNumber,
+      Palette* newPalette);     // Can be NULL to create a new palette
 
     // Changes the image pixel format. The dithering method is used only
     // when you want to convert from RGB to Indexed.
-    Image* convert_pixel_format(const Image* image,
-                                PixelFormat pixelFormat,
-                                DitheringMethod ditheringMethod,
-                                const RgbMap* rgbmap,
-                                const Palette* palette,
-                                bool is_background_layer);
+    Image* convert_pixel_format(
+      const Image* src,
+      Image* dst,         // Can be NULL to create a new image
+      PixelFormat pixelFormat,
+      DitheringMethod ditheringMethod,
+      const RgbMap* rgbmap,
+      const Palette* palette,
+      bool is_background);
 
   } // namespace quantization
 } // namespace raster
diff --git a/src/raster/rgbmap.cpp b/src/raster/rgbmap.cpp
index 0fb6d3cff..25ffa8426 100644
--- a/src/raster/rgbmap.cpp
+++ b/src/raster/rgbmap.cpp
@@ -22,85 +22,52 @@
 
 #include "raster/rgbmap.h"
 
-#include "raster/conversion_alleg.h"
+#include "raster/color_scales.h"
 #include "raster/palette.h"
 
-#include <allegro.h>
-
 namespace raster {
 
-class RgbMapImpl {
-public:
-  RgbMapImpl() {
-    m_allegMap = new RGB_MAP;
-    m_palette = NULL;
-    m_modifications = 0;
-  }
-
-  ~RgbMapImpl() {
-    delete m_allegMap;
-  }
-
-  bool match(const Palette* palette) const {
-    return (m_palette == palette &&
-            m_modifications == palette->getModifications());
-  }
-
-  void regenerate(const Palette* palette) {
-    m_palette = palette;
-    m_modifications = palette->getModifications();
-
-    PALETTE allegPal;
-    convert_palette_to_allegro(palette, allegPal);
-    create_rgb_table(m_allegMap, allegPal, NULL);
-
-    for (int r=0; r<32; ++r)
-      for (int g=0; g<32; ++g)
-        for (int b=0; b<32; ++b) {
-          if (m_allegMap->data[r][g][b] >= palette->size())
-            m_allegMap->data[r][g][b] = palette->findBestfit(_rgb_scale_5[r],
-                                                             _rgb_scale_5[g],
-                                                             _rgb_scale_5[b]);
-        }
-  }
-
-  int mapColor(int r, int g, int b) const {
-    ASSERT(r >= 0 && r < 256);
-    ASSERT(g >= 0 && g < 256);
-    ASSERT(b >= 0 && b < 256);
-    return m_allegMap->data[r>>3][g>>3][b>>3];
-  }
-
-private:
-  RGB_MAP* m_allegMap;
-  const Palette* m_palette;
-  int m_modifications;
-};
+#define MAPSIZE 32*32*32
 
 RgbMap::RgbMap()
   : Object(OBJECT_RGBMAP)
+  , m_map(MAPSIZE)
+  , m_palette(NULL)
+  , m_modifications(0)
 {
-  m_impl = new RgbMapImpl;
-}
-
-RgbMap::~RgbMap()
-{
-  delete m_impl;
 }
 
 bool RgbMap::match(const Palette* palette) const
 {
-  return m_impl->match(palette);
+  return (m_palette == palette &&
+    m_modifications == palette->getModifications());
 }
 
-void RgbMap::regenerate(const Palette* palette)
+void RgbMap::regenerate(const Palette* palette, int mask_index)
 {
-  m_impl->regenerate(palette);
+  m_palette = palette;
+  m_modifications = palette->getModifications();
+
+  int i = 0;
+  for (int r=0; r<32; ++r) {
+    for (int g=0; g<32; ++g) {
+      for (int b=0; b<32; ++b) {
+        m_map[i++] =
+          palette->findBestfit(
+            scale_5bits_to_8bits(r),
+            scale_5bits_to_8bits(g),
+            scale_5bits_to_8bits(b), mask_index);
+      }
+    }
+  }
 }
 
 int RgbMap::mapColor(int r, int g, int b) const
 {
-  return m_impl->mapColor(r, g, b);
+  ASSERT(r >= 0 && r < 256);
+  ASSERT(g >= 0 && g < 256);
+  ASSERT(b >= 0 && b < 256);
+  return m_map[((r>>3) << 10) + ((g>>3) << 5) + (b>>3)];
 }
 
 } // namespace raster
diff --git a/src/raster/rgbmap.h b/src/raster/rgbmap.h
index 4a92c0331..273f561f6 100644
--- a/src/raster/rgbmap.h
+++ b/src/raster/rgbmap.h
@@ -23,6 +23,8 @@
 #include "base/disable_copying.h"
 #include "raster/object.h"
 
+#include <vector>
+
 namespace raster {
 
   class Palette;
@@ -30,15 +32,16 @@ namespace raster {
   class RgbMap : public Object {
   public:
     RgbMap();
-    virtual ~RgbMap();
 
     bool match(const Palette* palette) const;
-    void regenerate(const Palette* palette);
+    void regenerate(const Palette* palette, int mask_index);
 
     int mapColor(int r, int g, int b) const;
 
   private:
-    class RgbMapImpl* m_impl;
+    std::vector<uint8_t> m_map;
+    const Palette* m_palette;
+    int m_modifications;
 
     DISABLE_COPYING(RgbMap);
   };
diff --git a/src/raster/sprite.cpp b/src/raster/sprite.cpp
index bd832c7d3..8a5b9aeca 100644
--- a/src/raster/sprite.cpp
+++ b/src/raster/sprite.cpp
@@ -278,13 +278,16 @@ void Sprite::deletePalette(Palette* pal)
 
 RgbMap* Sprite::getRgbMap(FrameNumber frame)
 {
+  int mask_color = (getBackgroundLayer() ? -1: getTransparentColor());
+
   if (m_rgbMap == NULL) {
     m_rgbMap = new RgbMap();
-    m_rgbMap->regenerate(getPalette(frame));
+    m_rgbMap->regenerate(getPalette(frame), mask_color);
   }
   else if (!m_rgbMap->match(getPalette(frame))) {
-    m_rgbMap->regenerate(getPalette(frame));
+    m_rgbMap->regenerate(getPalette(frame), mask_color);
   }
+
   return m_rgbMap;
 }