(not working yet)

gdal-resampling-alpha-fix.patch

Index: alg/gdalwarper.cpp
===================================================================
--- alg/gdalwarper.cpp	(revision 21094)
+++ alg/gdalwarper.cpp	(working copy)
@@ -32,6 +32,7 @@
 #include "cpl_minixml.h"
 #include "ogr_api.h"
 #include "gdal_priv.h"
+#include <iostream>
 
 CPL_CVSID("$Id$");
 
@@ -159,7 +160,14 @@
         GDALRasterBandH hBand = GDALGetRasterBand( hSrcDS, iBand+1 );
         int             bGotNoData = FALSE;
         double          dfNoDataValue;
-        
+
+        std::cout << "band " << iBand << " interpretation: " << GDALGetRasterColorInterpretation(hBand) << "\n";
+
+        if (GDALGetRasterColorInterpretation(hBand) == GCI_AlphaBand)
+        {
+            psWOptions->nSrcAlphaBand = iBand + 1;
+        }
+
         dfNoDataValue = GDALGetRasterNoDataValue( hBand, &bGotNoData );
         if( bGotNoData )
         {
Index: swig/python/scripts/gdal_retile.py
===================================================================
--- swig/python/scripts/gdal_retile.py	(revision 21094)
+++ swig/python/scripts/gdal_retile.py	(working copy)
@@ -165,6 +165,11 @@
            self.ct = ct.Clone()
         else:
            self.ct = None
+        self.ci = [0] * self.bands
+        for iband in range(self.bands):
+            ci = fhInputTile.GetRasterBand(iband + 1).GetColorInterpretation()
+            self.ci[iband] = ci
+            print "1. band=%s, ci=%s" % (iband+1, ci)
 
         extent = self.ogrTileIndexDS.GetLayer().GetExtent()
         self.ulx = extent[0];
@@ -428,10 +433,13 @@
 
     t_fh.SetGeoTransform( geotransform )
     t_fh.SetProjection( levelMosaicInfo.projection)
-    if levelMosaicInfo.ct is not None:
-        for band in range(1,bands+1):
-            t_band = t_fh.GetRasterBand( band )
+    for band in range(1,bands+1):
+        t_band = t_fh.GetRasterBand( band )
+        if levelMosaicInfo.ct is not None:
             t_band.SetRasterColorTable(levelMosaicInfo.ct)
+        ci = levelMosaicInfo.ci[band-1]
+        print "2. band=%s, ci=%s" % (band, ci)
+        t_band.SetRasterColorInterpretation(ci)
 
     res = gdal.ReprojectImage(s_fh,t_fh,None,None,ResamplingMethod)
     if  res!=0: