added wxImage::CanRead

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@3421 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/imagbmp.cpp

@@ -401,6 +401,15 @@ bool wxBMPHandler::LoadFile( wxImage *image, wxInputStream& stream, bool WXUNUSE
      return TRUE;
 }
 
+bool wxBMPHandler::CanRead( wxInputStream& stream )
+{
+    unsigned char hdr[2];
+    
+    stream.Read(&hdr, 2);
+    stream.SeekI(-2, wxFromCurrent);
+    return (hdr[0] == 'B' && hdr[1] == 'M');
+}
+
 #endif // wxUSE_STREAMS
 
 

src/common/image.cpp

@@ -436,23 +436,14 @@ bool wxImage::LoadFile( wxInputStream& stream, long type )
 
     if (type==wxBITMAP_TYPE_ANY)
     {
-      // here we can try to guess the handler according the extension,
-      // but we lose the stream name !?
-      // Probably we should write methods such as 
-      // bool wxImageHandler::CanRead(wxString&)
-      // bool wxImageHandler::CanRead(sxInputStream&&)
-      // for png : see example.c
 	wxList &list=GetHandlers();
-	off_t pos=stream.TellI();
-
-	 wxLogNull prevent_log;
 
 	for ( wxList::Node *node = list.GetFirst(); node; node = node->GetNext() )
 	{  
  	    handler=(wxImageHandler*)node->GetData();
-	    if (handler->LoadFile( this, stream, FALSE )) return TRUE;
+        if (handler->CanRead( stream ))
+            return handler->LoadFile( this, stream );
 
-	    stream.SeekI(pos);
 	}
 
 	wxLogWarning( _T("No handler found for this image.") );
@@ -637,6 +628,33 @@ bool wxImageHandler::SaveFile( wxImage *WXUNUSED(image), wxOutputStream& WXUNUSE
 {
     return FALSE;
 }
+
+bool wxImageHandler::CanRead( wxInputStream& stream )
+{
+    return FALSE;
+}
+
+bool wxImageHandler::CanRead( const wxString& name )
+{
+#if wxUSE_STREAMS
+    if (wxFileExists(name))
+    {
+        wxFileInputStream stream(name);
+        return CanRead(stream);
+    }
+
+    else {
+        wxLogError( _T("Can't check image format of file '%s': file does not exist."), name.c_str() );
+
+        return FALSE;
+    }
+#else // !wxUSE_STREAMS
+    return FALSE;
+#endif // wxUSE_STREAMS
+}
+
+
+
 #endif // wxUSE_STREAMS
 
 //-----------------------------------------------------------------------------

src/common/imaggif.cpp

@@ -66,4 +66,13 @@ bool wxGIFHandler::SaveFile( wxImage * WXUNUSED(image),
     return FALSE;
 }
 
+bool wxGIFHandler::CanRead( wxInputStream& stream )
+{
+    unsigned char hdr[5];
+    
+    stream.Read(&hdr, 5);
+    stream.SeekI(-5, wxFromCurrent);
+    return (hdr[0] == 'G' && hdr[1] == 'I' && hdr[2] == 'F' && hdr[3] == '8' && hdr[4] == '9');
+}
+
 #endif

src/common/imagjpeg.cpp

@@ -310,6 +310,16 @@ bool wxJPEGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbo
     return TRUE;
 }
 
+
+bool wxJPEGHandler::CanRead( wxInputStream& stream )
+{
+    unsigned char hdr[2];
+    
+    stream.Read(&hdr, 2);
+    stream.SeekI(-2, wxFromCurrent);
+    return (hdr[0] == 0xFF && hdr[1] == 0xD8);
+}
+
 #endif 
   // wxUSE_STREAMS
 

src/common/imagpng.cpp

@@ -346,6 +346,15 @@ bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbos
     return TRUE;
 }
 
+bool wxPNGHandler::CanRead( wxInputStream& stream )
+{
+    unsigned char hdr[4];
+    
+    stream.Read(&hdr, 4);    
+    stream.SeekI(-4, wxFromCurrent);
+    return (hdr[0] == 0x89 && hdr[1] == 'P' && hdr[2] == 'N' && hdr[3] == 'G');
+}
+
 #endif
   // wxUSE_STREAMS
 

src/common/imagpnm.cpp

@@ -136,6 +136,12 @@ bool wxPNMHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool WXUNUS
     return (stream.LastError()==wxStream_NOERROR);
 }
 
+bool wxPNMHandler::CanRead( wxInputStream& stream )
+{
+    return FALSE; // VS - temporary - FIXME
+}
+
+
 #endif // wxUSE_STREAMS