diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 152e137ec..dbe1ce0f2 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -293,6 +293,7 @@ add_library(aseprite-library
   util/celmove.cpp
   util/clipboard.cpp
   util/col_file.cpp
+  util/expand_cel_canvas.cpp
   util/filetoks.cpp
   util/misc.cpp
   util/msk_file.cpp
diff --git a/src/util/expand_cel_canvas.cpp b/src/util/expand_cel_canvas.cpp
new file mode 100644
index 000000000..d27541dac
--- /dev/null
+++ b/src/util/expand_cel_canvas.cpp
@@ -0,0 +1,221 @@
+/* ASE - Allegro Sprite Editor
+ * Copyright (C) 2001-2011  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 "config.h"
+
+#include "util/expand_cel_canvas.h"
+
+#include "base/unique_ptr.h"
+#include "document.h"
+#include "raster/cel.h"
+#include "raster/dirty.h"
+#include "raster/layer.h"
+#include "raster/sprite.h"
+#include "raster/stock.h"
+#include "undo/undo_history.h"
+#include "undoers/add_cel.h"
+#include "undoers/add_image.h"
+#include "undoers/close_group.h"
+#include "undoers/dirty_area.h"
+#include "undoers/open_group.h"
+#include "undoers/replace_image.h"
+#include "undoers/set_cel_position.h"
+
+ExpandCelCanvas::ExpandCelCanvas(Document* document, Sprite* sprite, Layer* layer, TiledMode tiledMode)
+  : m_document(document)
+  , m_sprite(sprite)
+  , m_layer(layer)
+  , m_cel(NULL)
+  , m_celImage(NULL)
+  , m_celCreated(false)
+  , m_closed(false)
+  , m_committed(false)
+{
+  if (m_layer->is_image()) {
+    m_cel = static_cast<LayerImage*>(layer)->getCel(m_sprite->getCurrentFrame());
+    if (m_cel)
+      m_celImage = m_sprite->getStock()->getImage(m_cel->getImage());
+  }
+
+  // If there is no Cel
+  if (m_cel == NULL) {
+    // Create the image
+    m_celImage = image_new(m_sprite->getImgType(), m_sprite->getWidth(), m_sprite->getHeight());
+    image_clear(m_celImage,
+		m_celImage->mask_color);
+
+    // create the cel
+    m_cel = new Cel(m_sprite->getCurrentFrame(), 0);
+    static_cast<LayerImage*>(m_layer)->addCel(m_cel);
+
+    m_celCreated = true;
+  }
+
+  m_originalCelX = m_cel->getX();
+  m_originalCelY = m_cel->getY();
+
+  // region to draw
+  int x1, y1, x2, y2;
+
+  if (tiledMode == TILED_NONE) { // non-tiled
+    x1 = MIN(m_cel->getX(), 0);
+    y1 = MIN(m_cel->getY(), 0);
+    x2 = MAX(m_cel->getX()+m_celImage->w, m_sprite->getWidth());
+    y2 = MAX(m_cel->getY()+m_celImage->h, m_sprite->getHeight());
+  }
+  else { 			// tiled
+    x1 = 0;
+    y1 = 0;
+    x2 = m_sprite->getWidth();
+    y2 = m_sprite->getHeight();
+  }
+
+  // create two copies of the image region which we'll modify with the tool
+  m_srcImage = image_crop(m_celImage,
+			  x1-m_cel->getX(),
+			  y1-m_cel->getY(), x2-x1, y2-y1,
+			  m_celImage->mask_color);
+
+  m_dstImage = image_new_copy(m_srcImage);
+
+  // We have to adjust the cel position to match the m_dstImage
+  // position (the new m_dstImage will be used in RenderEngine to
+  // draw this cel).
+  m_cel->setPosition(x1, y1);
+}
+
+ExpandCelCanvas::~ExpandCelCanvas()
+{
+  try {
+    if (!m_committed && !m_closed)
+      rollback();
+  }
+  catch (...) {
+    // Do nothing
+  }
+  delete m_srcImage;
+  delete m_dstImage;
+}
+
+void ExpandCelCanvas::commit()
+{
+  ASSERT(!m_closed);
+  ASSERT(!m_committed);
+
+  undo::UndoHistory* undo = m_document->getUndoHistory();
+
+  // If the size of each image is the same, we can create an undo
+  // with only the differences between both images.
+  if (m_cel->getX() == m_originalCelX &&
+      m_cel->getY() == m_originalCelY &&
+      m_celImage->w == m_dstImage->w &&
+      m_celImage->h == m_dstImage->h) {
+    // Was m_celImage created in the start of the tool-loop?.
+    if (m_celCreated) {
+      // We can keep the m_celImage
+	  
+      // We copy the destination image to the m_celImage
+      image_copy(m_celImage, m_dstImage, 0, 0);
+
+      // Add the m_celImage in the images stock of the sprite.
+      m_cel->setImage(m_sprite->getStock()->addImage(m_celImage));
+
+      // Is the undo enabled?.
+      if (undo->isEnabled()) {
+	// We can temporary remove the cel.
+	static_cast<LayerImage*>(m_sprite->getCurrentLayer())->removeCel(m_cel);
+
+	// We create the undo information (for the new m_celImage
+	// in the stock and the new cel in the layer)...
+	undo->pushUndoer(new undoers::OpenGroup());
+	undo->pushUndoer(new undoers::AddImage(undo->getObjects(),
+					       m_sprite->getStock(), m_cel->getImage()));
+	undo->pushUndoer(new undoers::AddCel(undo->getObjects(),
+					     m_sprite->getCurrentLayer(), m_cel));
+	undo->pushUndoer(new undoers::CloseGroup());
+
+	// And finally we add the cel again in the layer.
+	static_cast<LayerImage*>(m_sprite->getCurrentLayer())->addCel(m_cel);
+      }
+    }
+    // If the m_celImage was already created before the whole process...
+    else {
+      // Add to the undo history the differences between m_celImage and m_dstImage
+      if (undo->isEnabled()) {
+	UniquePtr<Dirty> dirty(new Dirty(m_celImage, m_dstImage));
+
+	dirty->saveImagePixels(m_celImage);
+	if (dirty != NULL)
+	  undo->pushUndoer(new undoers::DirtyArea(undo->getObjects(), m_celImage, dirty));
+      }
+
+      // Copy the destination to the cel image.
+      image_copy(m_celImage, m_dstImage, 0, 0);
+    }
+  }
+  // If the size of both images are different, we have to
+  // replace the entire image.
+  else {
+    if (undo->isEnabled()) {
+      undo->pushUndoer(new undoers::OpenGroup());
+
+      if (m_cel->getX() != m_originalCelX ||
+	  m_cel->getY() != m_originalCelY) {
+	int x = m_cel->getX();
+	int y = m_cel->getY();
+	m_cel->setPosition(m_originalCelX, m_originalCelY);
+
+	undo->pushUndoer(new undoers::SetCelPosition(undo->getObjects(), m_cel));
+
+	m_cel->setPosition(x, y);
+      }
+
+      undo->pushUndoer(new undoers::ReplaceImage(undo->getObjects(),
+						 m_sprite->getStock(), m_cel->getImage()));
+      undo->pushUndoer(new undoers::CloseGroup());
+    }
+
+    // Replace the image in the stock.
+    m_sprite->getStock()->replaceImage(m_cel->getImage(), m_dstImage);
+
+    // Destroy the old cel image.
+    image_free(m_celImage);
+
+    // Now the m_dstImage is used, so we haven't to destroy it.
+    m_dstImage = NULL;
+  }
+
+  m_committed = true;
+}
+
+void ExpandCelCanvas::rollback()
+{
+  ASSERT(!m_closed);
+  ASSERT(!m_committed);
+
+  // Here we destroy the temporary 'cel' created and restore all as it was before
+  m_cel->setPosition(m_originalCelX, m_originalCelY);
+
+  if (m_celCreated) {
+    static_cast<LayerImage*>(m_layer)->removeCel(m_cel);
+    delete m_cel;
+    delete m_celImage;
+  }
+
+  m_closed = true;
+}
diff --git a/src/util/expand_cel_canvas.h b/src/util/expand_cel_canvas.h
new file mode 100644
index 000000000..9ecd0103a
--- /dev/null
+++ b/src/util/expand_cel_canvas.h
@@ -0,0 +1,80 @@
+/* ASE - Allegro Sprite Editor
+ * Copyright (C) 2001-2011  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 UTIL_EXPAND_CEL_CANVAS_H_INCLUDED
+#define UTIL_EXPAND_CEL_CANVAS_H_INCLUDED
+
+#include "filters/tiled_mode.h"
+
+class Cel;
+class Document;
+class Image;
+class Layer;
+class Sprite;
+
+// This class can be used to expand the canvas of the current cel to
+// the visible portion of sprite. If the user cancels the operation,
+// you've a rollback() method to restore the cel to its original
+// state.  If all changes are committed, some undo information is
+// stored in the document's UndoHistory to go back to the original
+// state using "Undo" command.
+class ExpandCelCanvas
+{
+public:
+  ExpandCelCanvas(Document* document, Sprite* sprite, Layer* layer, TiledMode tiledMode);
+  ~ExpandCelCanvas();
+
+  // Commit changes made in getDestCanvas() in the cel's image. Adds
+  // information in the undo history so the user can undo the
+  // modifications in the canvas.
+  void commit();
+
+  // Restore the cel as its original state as when ExpandCelCanvas()
+  // was created.
+  void rollback();
+
+  // You can read pixels from here
+  Image* getSourceCanvas() {	// TODO this should be "const"
+    return m_srcImage;
+  }
+
+  // You can write pixels right here
+  Image* getDestCanvas() {
+    return m_dstImage;
+  }
+
+  const Cel* getCel() const {
+    return m_cel;
+  }
+
+private:
+  Document* m_document;
+  Sprite* m_sprite;
+  Layer* m_layer;
+  Cel* m_cel;
+  Image* m_celImage;
+  bool m_celCreated;
+  int m_originalCelX;
+  int m_originalCelY;
+  Image* m_srcImage;
+  Image* m_dstImage;
+  bool m_closed;
+  bool m_committed;
+};
+
+#endif
diff --git a/src/widgets/editor/tool_loop_impl.cpp b/src/widgets/editor/tool_loop_impl.cpp
index 6a973bc93..a6e3dac69 100644
--- a/src/widgets/editor/tool_loop_impl.cpp
+++ b/src/widgets/editor/tool_loop_impl.cpp
@@ -23,32 +23,22 @@
 #include "app.h"
 #include "app/color.h"
 #include "app/color_utils.h"
-#include "base/unique_ptr.h"
 #include "context.h"
 #include "gui/gui.h"
 #include "modules/editors.h"
 #include "raster/cel.h"
-#include "raster/dirty.h"
-#include "raster/image.h"
 #include "raster/layer.h"
 #include "raster/mask.h"
 #include "raster/pen.h"
 #include "raster/sprite.h"
-#include "raster/stock.h"
 #include "settings/settings.h"
 #include "tools/ink.h"
 #include "tools/tool.h"
 #include "tools/tool_loop.h"
 #include "undo/undo_history.h"
-#include "undoers/add_cel.h"
-#include "undoers/add_image.h"
-#include "undoers/close_group.h"
-#include "undoers/dirty_area.h"
-#include "undoers/open_group.h"
-#include "undoers/replace_image.h"
-#include "undoers/set_cel_position.h"
-#include "widgets/editor/editor.h"
+#include "util/expand_cel_canvas.h"
 #include "widgets/color_bar.h"
+#include "widgets/editor/editor.h"
 #include "widgets/statebar.h"
 
 #include <allegro.h>
@@ -63,17 +53,11 @@ class ToolLoopImpl : public tools::ToolLoop
   Sprite* m_sprite;
   Layer* m_layer;
   Cel* m_cel;
-  Image* m_cel_image;
-  bool m_cel_created;
-  int m_old_cel_x;
-  int m_old_cel_y;
   bool m_filled;
   bool m_previewFilled;
   int m_sprayWidth;
   int m_spraySpeed;
   TiledMode m_tiled_mode;
-  Image* m_src_image;
-  Image* m_dst_image;
   bool m_useMask;
   Mask* m_mask;
   gfx::Point m_maskOrigin;
@@ -85,6 +69,7 @@ class ToolLoopImpl : public tools::ToolLoop
   tools::ToolLoop::Button m_button;
   int m_primary_color;
   int m_secondary_color;
+  ExpandCelCanvas m_expandCelCanvas;
 
 public:
   ToolLoopImpl(Editor* editor,
@@ -102,19 +87,16 @@ public:
     , m_document(document)
     , m_sprite(sprite)
     , m_layer(layer)
-    , m_cel(NULL)
-    , m_cel_image(NULL)
-    , m_cel_created(false)
     , m_canceled(false)
+    , m_tiled_mode(m_context->getSettings()->getTiledMode())
     , m_button(button)
     , m_primary_color(color_utils::color_for_layer(primary_color, layer))
     , m_secondary_color(color_utils::color_for_layer(secondary_color, layer))
+    , m_expandCelCanvas(document, sprite, layer, m_tiled_mode)
   {
     // Settings
     ISettings* settings = m_context->getSettings();
 
-    m_tiled_mode = settings->getTiledMode();
-
     switch (tool->getFill(m_button)) {
       case tools::FillNone:
 	m_filled = false;
@@ -139,54 +121,6 @@ public:
 		    pen_settings->getSize(),
 		    pen_settings->getAngle());
     
-    // Get cel and image where we can draw
-
-    if (m_layer->is_image()) {
-      m_cel = static_cast<LayerImage*>(sprite->getCurrentLayer())->getCel(sprite->getCurrentFrame());
-      if (m_cel)
-	m_cel_image = sprite->getStock()->getImage(m_cel->getImage());
-    }
-
-    if (m_cel == NULL) {
-      // create the image
-      m_cel_image = image_new(sprite->getImgType(), sprite->getWidth(), sprite->getHeight());
-      image_clear(m_cel_image,
-		  m_cel_image->mask_color);
-
-      // create the cel
-      m_cel = new Cel(sprite->getCurrentFrame(), 0);
-      static_cast<LayerImage*>(sprite->getCurrentLayer())->addCel(m_cel);
-
-      m_cel_created = true;
-    }
-
-    m_old_cel_x = m_cel->getX();
-    m_old_cel_y = m_cel->getY();
-
-    // region to draw
-    int x1, y1, x2, y2;
-
-    // non-tiled
-    if (m_tiled_mode == TILED_NONE) {
-      x1 = MIN(m_cel->getX(), 0);
-      y1 = MIN(m_cel->getY(), 0);
-      x2 = MAX(m_cel->getX()+m_cel_image->w, m_sprite->getWidth());
-      y2 = MAX(m_cel->getY()+m_cel_image->h, m_sprite->getHeight());
-    }
-    else { 			// tiled
-      x1 = 0;
-      y1 = 0;
-      x2 = m_sprite->getWidth();
-      y2 = m_sprite->getHeight();
-    }
-
-    // create two copies of the image region which we'll modify with the tool
-    m_src_image = image_crop(m_cel_image,
-			     x1-m_cel->getX(),
-			     y1-m_cel->getY(), x2-x1, y2-y1,
-			     m_cel_image->mask_color);
-    m_dst_image = image_new_copy(m_src_image);
-
     m_useMask = m_document->isMaskVisible();
 
     // Selection ink
@@ -195,6 +129,9 @@ public:
       m_document->setMask(&emptyMask);
     }
 
+    int x1 = m_expandCelCanvas.getCel()->getX();
+    int y1 = m_expandCelCanvas.getCel()->getY();
+
     m_mask = m_document->getMask();
     m_maskOrigin = (!m_mask->is_empty() ? gfx::Point(m_mask->x-x1, m_mask->y-y1):
 					  gfx::Point(0, 0));
@@ -204,9 +141,6 @@ public:
     m_speed.x = 0;
     m_speed.y = 0;
 
-    // we have to modify the cel position because it's used in the
-    // `render_sprite' routine to draw the `dst_image'
-    m_cel->setPosition(x1, y1);
     m_offset.x = -x1;
     m_offset.y = -y1;
 
@@ -227,112 +161,21 @@ public:
   ~ToolLoopImpl()
   {
     if (!m_canceled) {
-      undo::UndoHistory* undo = m_document->getUndoHistory();
-
       // Paint ink
       if (getInk()->isPaint()) {
-	// If the size of each image is the same, we can create an
-	// undo with only the differences between both images.
-	if (m_cel->getX() == m_old_cel_x &&
-	    m_cel->getY() == m_old_cel_y &&
-	    m_cel_image->w == m_dst_image->w &&
-	    m_cel_image->h == m_dst_image->h) {
-	  // Was the 'cel_image' created in the start of the tool-loop?.
-	  if (m_cel_created) {
-	    // Then we can keep the 'cel_image'...
-	  
-	    // We copy the 'destination' image to the 'cel_image'.
-	    image_copy(m_cel_image, m_dst_image, 0, 0);
-
-	    // Add the 'cel_image' in the images' stock of the sprite.
-	    m_cel->setImage(m_sprite->getStock()->addImage(m_cel_image));
-
-	    // Is the undo enabled?.
-	    if (undo->isEnabled()) {
-	      // We can temporary remove the cel.
-	      static_cast<LayerImage*>(m_sprite->getCurrentLayer())->removeCel(m_cel);
-
-	      // We create the undo information (for the new cel_image
-	      // in the stock and the new cel in the layer)...
-	      undo->pushUndoer(new undoers::OpenGroup());
-	      undo->pushUndoer(new undoers::AddImage(undo->getObjects(),
-		  m_sprite->getStock(), m_cel->getImage()));
-	      undo->pushUndoer(new undoers::AddCel(undo->getObjects(),
-		  m_sprite->getCurrentLayer(), m_cel));
-	      undo->pushUndoer(new undoers::CloseGroup());
-
-	      // And finally we add the cel again in the layer.
-	      static_cast<LayerImage*>(m_sprite->getCurrentLayer())->addCel(m_cel);
-	    }
-	  }
-	  else {
-	    // Undo the dirty region.
-	    if (undo->isEnabled()) {
-	      UniquePtr<Dirty> dirty(new Dirty(m_cel_image, m_dst_image));
-
-	      dirty->saveImagePixels(m_cel_image);
-	      if (dirty != NULL)
-		undo->pushUndoer(new undoers::DirtyArea(undo->getObjects(),
-							m_cel_image, dirty));
-	    }
-
-	    // Copy the 'dst_image' to the cel_image.
-	    image_copy(m_cel_image, m_dst_image, 0, 0);
-	  }
-	}
-	// If the size of both images are different, we have to
-	// replace the entire image.
-	else {
-	  if (undo->isEnabled()) {
-	    undo->pushUndoer(new undoers::OpenGroup());
-
-	    if (m_cel->getX() != m_old_cel_x ||
-		m_cel->getY() != m_old_cel_y) {
-	      int x = m_cel->getX();
-	      int y = m_cel->getY();
-	      m_cel->setPosition(m_old_cel_x, m_old_cel_y);
-
-	      undo->pushUndoer(new undoers::SetCelPosition(undo->getObjects(), m_cel));
-
-	      m_cel->setPosition(x, y);
-	    }
-
-	    undo->pushUndoer(new undoers::ReplaceImage(undo->getObjects(),
-		m_sprite->getStock(), m_cel->getImage()));
-	    undo->pushUndoer(new undoers::CloseGroup());
-	  }
-
-	  // Replace the image in the stock.
-	  m_sprite->getStock()->replaceImage(m_cel->getImage(), m_dst_image);
-
-	  // Destroy the old cel image.
-	  image_free(m_cel_image);
-
-	  // Now the `dst_image' is used, so we haven't to destroy it.
-	  m_dst_image = NULL;
-	}
+	m_expandCelCanvas.commit();
       }
-
       // Selection ink
-      if (getInk()->isSelection())
+      else if (getInk()->isSelection()) {
 	m_document->generateMaskBoundaries();
+      }
     }
 
     // If the trace was not canceled or it is not a 'paint' ink...
     if (m_canceled || !getInk()->isPaint()) {
-      // Here we destroy the temporary 'cel' created and restore all as it was before
-
-      m_cel->setPosition(m_old_cel_x, m_old_cel_y);
-
-      if (m_cel_created) {
-	static_cast<LayerImage*>(m_layer)->removeCel(m_cel);
-	delete m_cel;
-	delete m_cel_image;
-      }
+      m_expandCelCanvas.rollback();
     }
 
-    delete m_src_image;
-    delete m_dst_image;
     delete m_pen;
   }
 
@@ -343,8 +186,8 @@ public:
   Document* getDocument() { return m_document; }
   Sprite* getSprite() { return m_sprite; }
   Layer* getLayer() { return m_layer; }
-  Image* getSrcImage() { return m_src_image; }
-  Image* getDstImage() { return m_dst_image; }
+  Image* getSrcImage() { return m_expandCelCanvas.getSourceCanvas(); }
+  Image* getDstImage() { return m_expandCelCanvas.getDestCanvas(); }
   bool useMask() { return m_useMask; }
   Mask* getMask() { return m_mask; }
   gfx::Point getMaskOrigin() { return m_maskOrigin; }