+ added a "shared" parameter to select if you want to open the dataset in shared mode (causing problems when multiple accesses to the same file)

+ introduced some more code for supporting overviews (still commented out as default, need revision)

plugins/input/gdal/gdal_datasource.cpp

@@ -24,6 +24,10 @@
 #include "gdal_datasource.hpp"
 #include "gdal_featureset.hpp"
 
+// mapnik
+#include <mapnik/ptree_helpers.hpp>
+#include <mapnik/geom_util.hpp>
+
 
 using mapnik::datasource;
 using mapnik::parameters;
@@ -40,6 +44,7 @@ using mapnik::datasource_exception;
 gdal_datasource::gdal_datasource(parameters const& params)
    : datasource(params),
      extent_(),
+     dataset_(0),
      desc_(*params.get<std::string>("type"),"utf-8")
 {
    GDALAllRegister();
@@ -53,7 +58,15 @@ gdal_datasource::gdal_datasource(parameters const& params)
    else
       dataset_name_ = *file;
 
-   dataset_ = boost::shared_ptr<GDALDataset>(reinterpret_cast<GDALDataset*>(GDALOpenShared((dataset_name_).c_str(),GA_ReadOnly)));
+   shared_dataset_ = *params_.get<mapnik::boolean>("shared",false);
+
+#if GDAL_VERSION_NUM >= 1600
+   if (shared_dataset_)
+       dataset_ = reinterpret_cast<GDALDataset*>(GDALOpenShared((dataset_name_).c_str(),GA_ReadOnly));
+   else
+#endif
+       dataset_ = reinterpret_cast<GDALDataset*>(GDALOpen((dataset_name_).c_str(),GA_ReadOnly));
+
    if (! dataset_) throw datasource_exception(CPLGetLastErrorMsg());
 
    double tr[6];
@@ -67,8 +80,7 @@ gdal_datasource::gdal_datasource(parameters const& params)
 
 gdal_datasource::~gdal_datasource()
 {
-    GDALDereferenceDataset (dataset_.get());
+    GDALClose (dataset_);
-    dataset_.reset(); // prevent delete of dataset
 }
 
 int gdal_datasource::type() const

plugins/input/gdal/gdal_datasource.hpp

@@ -42,8 +42,9 @@ class gdal_datasource : public mapnik::datasource
    private:
       mapnik::Envelope<double> extent_;
       std::string dataset_name_;
-      boost::shared_ptr<GDALDataset> dataset_;
+      GDALDataset* dataset_;
       mapnik::layer_descriptor desc_;
+      bool shared_dataset_;
 };
 
 

plugins/input/gdal/gdal_featureset.cpp

@@ -43,26 +43,93 @@ feature_ptr gdal_featureset::next()
    {
       first_ = false;
       feature_ptr feature(new Feature(1));
+
       GDALRasterBand * red = 0;
       GDALRasterBand * green = 0;
       GDALRasterBand * blue = 0;
       GDALRasterBand * alpha = 0;
       GDALRasterBand * grey = 0; 
-      for (int i = 0; i < dataset_.GetRasterCount() ;++i)
+
+      unsigned raster_xsize = dataset_.GetRasterXSize();
+      unsigned raster_ysize = dataset_.GetRasterYSize();
+      int nbands = dataset_.GetRasterCount();
+
+      double tr[6];
+      dataset_.GetGeoTransform(tr);
+      double x0 = tr[0];
+      double y0 = tr[3];
+      double x1 = tr[0] + raster_xsize * tr[1] + raster_ysize * tr[2];
+      double y1 = tr[3] + raster_xsize * tr[4] + raster_ysize * tr[5];
+      Envelope<double> raster_extent(x0,y0,x1,y1);
+      CoordTransform t (raster_xsize,raster_ysize,raster_extent,0,0);
+      Envelope<double> intersection = raster_extent.intersect(query_extent_);
+      Envelope<double> box = t.forward(intersection);
+      
+      int start_x = int(box.minx()+0.5);
+      int start_y = int(box.miny()+0.5);
+      int width = int(box.width()+0.5);
+      int height = int(box.height()+0.5);
+
+#ifdef MAPNIK_DEBUG         
+      std::cout << boost::format("RasterWidth=%d RasterHeight=%d \n") % raster_xsize % raster_ysize;
+      std::cout << boost::format("StartX=%d StartY=%d Width=%d Height=%d \n") % start_x % start_y % width % height;
+#endif
+
+      if (width > 0 && height > 0)
+      {
+         // Some GDAL drivers operate more efficiently if they know in advance 
+         // what set of upcoming read requests will be made. The AdviseRead() 
+         // method allows an application to notify the driver of the region and
+         // bands of interest, and at what resolution the region will be read.
+         //
+         // dataset_.AdviseRead (start_x, start_y, width, height, width, height, GDT_Byte, nbands, NULL, NULL);
+
+         for (int i = 0; i < nbands; ++i)
          {
             GDALRasterBand * band = dataset_.GetRasterBand(i+1);
-         //if (band->GetOverviewCount() > 0)
+            int band_overviews = band->GetOverviewCount();
-         //{
+         
-         //  band = band->GetOverview(0);
+            if (band_overviews > 0)
-         //}
+            {
+#ifdef MAPNIK_DEBUG
+                for (int b = 0; b < band_overviews; b++)
+                {
+                    GDALRasterBand * overview = band->GetOverview (b);
+                    std::cout << boost::format("Overview=%d Width=%d Height=%d \n")
+                                           % b % overview->GetXSize() % overview->GetYSize();
+                }
+#endif
+
+#if 0
+                for (int b = band_overviews; --b >= 0;)
+                {
+                    GDALRasterBand * overview = band->GetOverview (b);
+                    if ((start_x + width) <= overview->GetXSize()
+                         && (start_y + height) <= overview->GetYSize())
+                    {
+#ifdef MAPNIK_DEBUG
+                        std::cout << boost::format("Picked Overview=%d \n") %b;
+#endif
+                        band = overview;
+                        break;
+                    }
+                }
+
+                // band = band->GetRasterSampleOverview (width / height);
+                // band = band->GetOverview (band->GetOverviewCount() - 1);
+#endif
+            }
          
 #ifdef MAPNIK_DEBUG     
             int bsx,bsy;
+            double scale;
             band->GetBlockSize(&bsx,&bsy);
-         std::cout << boost::format("Block=%dx%d Type=%s Color=%s \n") % bsx % bsy
+            scale = band->GetScale();
+            std::cout << boost::format("Block=%dx%d Scale=%f Type=%s Color=%s \n") % bsx % bsy % scale
                % GDALGetDataTypeName(band->GetRasterDataType())
                % GDALGetColorInterpretationName(band->GetColorInterpretation());   
 #endif
+
             GDALColorInterp color_interp = band->GetColorInterpretation();
             switch (color_interp)
             {
@@ -108,54 +175,35 @@ feature_ptr gdal_featureset::next()
                   break;	
                default:
                   break;
-               ;
             }
          }
       
-      unsigned raster_xsize = dataset_.GetRasterXSize();
-      unsigned raster_ysize = dataset_.GetRasterYSize();
-      double tr[6];
-      dataset_.GetGeoTransform(tr);
-      double x0 = tr[0];
-      double y0 = tr[3];
-      double x1 = tr[0] + raster_xsize * tr[1] + raster_ysize * tr[2];
-      double y1 = tr[3] + raster_xsize * tr[4] + raster_ysize * tr[5];
-      Envelope<double> raster_extent(x0,y0,x1,y1);
-      CoordTransform t (raster_xsize,raster_ysize,raster_extent,0,0);
-      Envelope<double> intersection = raster_extent.intersect(query_extent_);
-      Envelope<double> box = t.forward(intersection);
-      
-      int start_x = int(box.minx()+0.5);
-      int start_y = int(box.miny()+0.5);
-      int width = int(box.width()+0.5);
-      int height = int(box.height()+0.5);
-      
-      if (width > 0 && height > 0)
-      {
          mapnik::ImageData32 image(width,height);
          image.set(0xffffffff);
          
          if (red && green && blue)
          {
+            //red->AdviseRead  (start_x, start_y, width, height, width, height, GDT_Byte, nbands, NULL);
+            //green->AdviseRead(start_x, start_y, width, height, width, height, GDT_Byte, nbands, NULL);
+            //blue->AdviseRead (start_x, start_y, width, height, width, height, GDT_Byte, nbands, NULL);
             red->RasterIO  (GF_Read,start_x,start_y,width,height, image.getBytes() + 0, width,height, GDT_Byte,4,4*width);
             green->RasterIO(GF_Read,start_x,start_y,width,height, image.getBytes() + 1, width,height, GDT_Byte,4,4*width);
             blue->RasterIO (GF_Read,start_x,start_y,width,height, image.getBytes() + 2, width,height, GDT_Byte,4,4*width);
-            if (alpha)
-            {
-               alpha->RasterIO(GF_Read,start_x,start_y,width,height, image.getBytes() + 3, width,height, GDT_Byte,4,4*width);
-            }
          }
          else if (grey)
          {
+            // grey->AdviseRead (start_x, start_y, width, height, width, height, GDT_Byte, nbands, NULL);
             grey->RasterIO(GF_Read,start_x,start_y,width,height,image.getBytes() + 0, width, height,GDT_Byte,4,4*width);
             grey->RasterIO(GF_Read,start_x,start_y,width,height,image.getBytes() + 1, width, height,GDT_Byte,4,4*width);
             grey->RasterIO(GF_Read,start_x,start_y,width,height,image.getBytes() + 2, width, height,GDT_Byte,4,4*width);
+         }
 
          if (alpha)
          {
+            //alpha->AdviseRead (start_x, start_y, width, height, width, height, GDT_Byte, nbands, NULL);
             alpha->RasterIO(GF_Read,start_x,start_y,width,height, image.getBytes() + 3, width,height, GDT_Byte,4,4*width);
          }
-         }
+
          feature->set_raster(mapnik::raster_ptr(new mapnik::raster(intersection,image)));
          return feature;
       }