diff --git a/src/render/software/Canvas.cpp b/src/render/software/Canvas.cpp
index 7cf1439..67cd6c0 100644
--- a/src/render/software/Canvas.cpp
+++ b/src/render/software/Canvas.cpp
@@ -11,7 +11,7 @@ Canvas::Canvas()
     vertical_portion_count = 1;
     width = 1;
     height = 1;
-    portions.push_back(new CanvasPortion());
+    portions.push_back(new CanvasPortion);
 
     preview = new CanvasPreview;
 }
@@ -41,13 +41,14 @@ void Canvas::setSize(int width, int height)
 
     int done_width = 0;
     int done_height = 0;
+    int index = 0;
 
     for (int y = 0; y < vertical_portion_count; y++)
     {
         done_width = 0;
         for (int x = 0; x < horizontal_portion_count; x++)
         {
-            CanvasPortion *portion = new CanvasPortion(preview);
+            CanvasPortion *portion = new CanvasPortion(index++, preview);
 
             portion->setSize((x == horizontal_portion_count - 1) ? width - done_width : portion_width,
                              (y == vertical_portion_count - 1) ? height - done_height : portion_height,
diff --git a/src/render/software/CanvasPortion.cpp b/src/render/software/CanvasPortion.cpp
index 193404a..c29fec9 100644
--- a/src/render/software/CanvasPortion.cpp
+++ b/src/render/software/CanvasPortion.cpp
@@ -4,6 +4,8 @@
 
 #include "CanvasPixel.h"
 #include "CanvasPreview.h"
+#include "PackStream.h"
+#include "FileSystem.h"
 
 #define CHECK_COORDINATES() assert(x >= 0); \
     assert(x < width); \
@@ -11,8 +13,8 @@
     assert(y < height); \
     assert(pixels != NULL)
 
-CanvasPortion::CanvasPortion(CanvasPreview* preview):
-    preview(preview)
+CanvasPortion::CanvasPortion(int index, CanvasPreview* preview):
+    index(index), preview(preview)
 {
     width = 1;
     height = 1;
@@ -70,15 +72,38 @@ void CanvasPortion::preparePixels()
     clear();
 }
 
-void CanvasPortion::discardPixels()
+void CanvasPortion::discardPixels(bool save)
 {
     if (pixels)
     {
+        if (save)
+        {
+            saveToDisk();
+        }
         delete[] pixels;
         pixels = NULL;
     }
 }
 
+void CanvasPortion::saveToDisk()
+{
+    if (pixels)
+    {
+        std::string filepath = FileSystem::getTempFile("paysages_portion_" + std::to_string(index) + ".dat");
+        PackStream stream;
+        stream.bindToFile(filepath, true);
+        stream.write(&width);
+        stream.write(&height);
+        for (int x = 0; x < width; x++)
+        {
+            for (int y = 0; y < height; y++)
+            {
+                pixels[y * width + x].getComposite().save(&stream);
+            }
+        }
+    }
+}
+
 void CanvasPortion::pushFragment(int x, int y, const CanvasFragment &fragment)
 {
     CHECK_COORDINATES();
diff --git a/src/render/software/CanvasPortion.h b/src/render/software/CanvasPortion.h
index 59d0153..326b826 100644
--- a/src/render/software/CanvasPortion.h
+++ b/src/render/software/CanvasPortion.h
@@ -16,8 +16,8 @@ namespace software {
 class SOFTWARESHARED_EXPORT CanvasPortion
 {
 public:
-    CanvasPortion(CanvasPreview* preview=NULL);
-    ~CanvasPortion();
+    CanvasPortion(int index=0, CanvasPreview *preview=NULL);
+    virtual ~CanvasPortion();
 
     inline int getWidth() const {return width;}
     inline int getHeight() const {return height;}
@@ -36,8 +36,15 @@ public:
 
     /**
      * Discard the memory used by pixels.
+     *
+     * If save is true, the portion will be saved to disk before.
      */
-    void discardPixels();
+    void discardPixels(bool save=true);
+
+    /**
+     * Save the portion to a picture file on disk.
+     */
+    void saveToDisk();
 
     /**
      * Add a fragment to the pixel located at (x, y).
@@ -61,12 +68,13 @@ public:
     void setColor(int x, int y, const Color &color);
 
 private:
+    int index;
     int width;
     int height;
     int xoffset;
     int yoffset;
     CanvasPixel *pixels;
-    CanvasPreview* preview;
+    CanvasPreview *preview;
 };
 
 }
diff --git a/src/system/FileSystem.cpp b/src/system/FileSystem.cpp
new file mode 100644
index 0000000..2ee3e45
--- /dev/null
+++ b/src/system/FileSystem.cpp
@@ -0,0 +1,8 @@
+#include "FileSystem.h"
+
+#include <QDir>
+
+std::string FileSystem::getTempFile(const std::string &filename)
+{
+    return QDir::temp().filePath(QString::fromStdString(filename)).toStdString();
+}
diff --git a/src/system/FileSystem.h b/src/system/FileSystem.h
new file mode 100644
index 0000000..afd2b3f
--- /dev/null
+++ b/src/system/FileSystem.h
@@ -0,0 +1,23 @@
+#ifndef FILESYSTEM_H
+#define FILESYSTEM_H
+
+#include "system_global.h"
+
+namespace paysages {
+namespace system {
+
+class SYSTEMSHARED_EXPORT FileSystem
+{
+public:
+    /**
+     * Get an absolute path to a temporary file.
+     *
+     * filename must not contain directory separators.
+     */
+    static std::string getTempFile(const std::string &filename);
+};
+
+}
+}
+
+#endif // FILESYSTEM_H
diff --git a/src/system/system.pro b/src/system/system.pro
index ceac911..0c1de8c 100644
--- a/src/system/system.pro
+++ b/src/system/system.pro
@@ -26,7 +26,8 @@ SOURCES += \
     Logs.cpp \
     ParallelPool.cpp \
     ParallelWorker.cpp \
-    Semaphore.cpp
+    Semaphore.cpp \
+    FileSystem.cpp
 
 HEADERS += \
     system_global.h \
@@ -42,7 +43,8 @@ HEADERS += \
     Logs.h \
     ParallelPool.h \
     ParallelWorker.h \
-    Semaphore.h
+    Semaphore.h \
+    FileSystem.h
 
 unix:!symbian {
     maemo5 {
diff --git a/src/system/system_global.h b/src/system/system_global.h
index 80b4d3c..769b128 100644
--- a/src/system/system_global.h
+++ b/src/system/system_global.h
@@ -21,6 +21,7 @@ namespace system {
     class Thread;
     class Mutex;
     class Semaphore;
+    class PictureWriter;
 }
 }
 using namespace paysages::system;