--- a/src/preview.cpp	Sat May 24 10:25:13 2014 +0900
+++ b/src/preview.cpp	Thu Jun 05 04:19:03 2014 +0900
@@ -1,5 +1,5 @@
 // Filename   : preview.cpp
-// Last Change: 23-May-2014.
+// Last Change: 04-Jun-2014.
 //
 
 #include "marksheet.h"
@@ -134,8 +134,10 @@
 {
 	wxBoxSizer* bSizerTop = new wxBoxSizer( wxHORIZONTAL );
 
-    m_scrolledWindow = new wxScrolledWindow( this, wxID_ANY, wxDefaultPosition, wxDefaultSize, wxALWAYS_SHOW_SB );
+    m_scrolledWindow = new wxScrolledWindow( this, wxID_ANY, wxDefaultPosition, wxDefaultSize, wxVSCROLL|wxALWAYS_SHOW_SB );
+    m_scrolledWindow->Connect( wxEVT_MOUSEWHEEL,  wxMouseEventHandler( PreviewDialog::OnWheel  ), NULL, this );
 	m_bitmap = new wxStaticBitmap( m_scrolledWindow, wxID_ANY, wxNullBitmap, wxDefaultPosition, wxDefaultSize, 0 );
+    m_bitmap->Connect( wxEVT_LEFT_DCLICK, wxMouseEventHandler( PreviewDialog::OnDClick ), NULL, this );
 	bSizerTop->Add( m_scrolledWindow, 1, wxALL|wxEXPAND, 5 );
 	
 	wxBoxSizer* bSizerMenu = new wxBoxSizer( wxVERTICAL );
@@ -164,31 +166,24 @@
 
 PreviewDialog::~PreviewDialog()
 {
+    m_scrolledWindow->Disconnect( wxEVT_MOUSEWHEEL,  wxMouseEventHandler( PreviewDialog::OnWheel  ), NULL, this );
+    m_bitmap->Disconnect( wxEVT_LEFT_DCLICK, wxMouseEventHandler( PreviewDialog::OnDClick ), NULL, this );
 }
 
 // Event Table
 BEGIN_EVENT_TABLE( PreviewDialog, wxDialog )
-    EVT_BUTTON( ID_PRINT,  PreviewDialog::OnPrint )
+    EVT_BUTTON( ID_PRINT, PreviewDialog::OnPrint )
 END_EVENT_TABLE()
 
 #define WIDTH  2480
 #define HEIGHT 3509
 void PreviewDialog::SetPreviewImage( int n )
 {
-    int w, h;
-    m_scrolledWindow->GetSize( &w, &h );
-    h = h * WIDTH / ( w - 200 );
+    m_preview = m_imagefiles[n];
+    m_zoom = 1.0;
+    SetZoom( m_zoom );
 
-    wxImage img;
-    img.LoadFile( m_imagefiles[n], wxBITMAP_TYPE_JPEG );
-    wxBitmap bmp( img.Scale( w, h, wxIMAGE_QUALITY_HIGH ) );
-    m_bitmap->SetBitmap( bmp );
-
-    m_scrolledWindow->Scroll( 0, 0 );
-    m_scrolledWindow->SetScrollbars( 10, 10, 0, h/10 );
-    m_preview = m_imagefiles[n];
-
-    //
+    // file info
     float z;
     long l;
     GetScore( &z, &l, m_imagefiles[n] );
@@ -198,6 +193,24 @@
     m_textInfo->SetValue( info );
 }
 
+void PreviewDialog::SetZoom( float zoom )
+{
+    int w, h;
+    m_scrolledWindow->GetSize( &w, &h );
+    w = (int)( zoom * h * WIDTH / HEIGHT );
+    h = (int)( zoom * h );
+
+    m_bitmap->SetBitmap( wxNullBitmap );
+    wxImage img;
+    img.LoadFile( m_preview, wxBITMAP_TYPE_JPEG );
+    wxBitmap bmp( img.Scale( w, h, wxIMAGE_QUALITY_HIGH ) );
+    m_bitmap->SetBitmap( bmp );
+    m_bitmap->Centre( wxHORIZONTAL );
+
+    m_scrolledWindow->Scroll( 0, 0 );
+    m_scrolledWindow->SetScrollbars( 10, 10, 0, h/10 );
+}
+
 void PreviewDialog::SetFiles( wxArrayString imagefiles, wxArrayString cachefiles, int select )
 { 
     m_imagefiles = imagefiles;
@@ -208,6 +221,31 @@
     this->SetTitle( title );
 }
 
+void PreviewDialog::OnWheel( wxMouseEvent& event )
+{
+    if ( event.ControlDown() ) {
+        if ( event.GetWheelRotation() < 0 ) {
+            if ( m_zoom > 2.1 ) return;
+            m_zoom *= 1.3;
+        }
+        else {
+            if ( m_zoom <= 1.0 ) return;
+            m_zoom /= 1.3;
+        }
+        SetZoom( m_zoom );
+        return;
+    }
+    event.Skip();
+}
+
+void PreviewDialog::OnDClick( wxMouseEvent& WXUNUSED(event) )
+{
+    if ( m_zoom > 2.1 ) m_zoom  = 1.0;
+    else                m_zoom *= 1.3;
+
+    SetZoom( m_zoom );
+}
+
 void PreviewDialog::OnPrint( wxCommandEvent& WXUNUSED(event) )
 {
     wxString html;