Make max_image_area a datasource parameter for GDAL.

plugins/input/gdal/gdal_datasource.cpp

@@ -83,6 +83,13 @@ gdal_datasource::gdal_datasource(parameters const& params)
     shared_dataset_ = *params.get<mapnik::boolean_type>("shared", false);
     band_ = *params.get<mapnik::value_integer>("band", -1);
     
+    // Maximum memory limitation for image will be simply based on the maximum
+    // area we allow for an image. The true memory footprint therefore will vary based
+    // on the type of imagery that exists. This is not the maximum size of an image
+    // on disk but rather the maximum size we will load into mapnik from GDAL.
+    // max_im_area based on 50 mb limit for RGBA
+    max_image_area_ = *params.get<mapnik::value_integer>("max_image_area", (50*1024*1024) / 4);
+
 #if GDAL_VERSION_NUM >= 1600
     if (shared_dataset_)
     {
@@ -235,7 +242,8 @@ featureset_ptr gdal_datasource::features(query const& q) const
                                               dx_,
                                               dy_,
                                               nodata_value_,
-                                              nodata_tolerance_);
+                                              nodata_tolerance_,
+                                              max_image_area_);
 }
 
 featureset_ptr gdal_datasource::features_at_point(coord2d const& pt, double tol) const
@@ -254,5 +262,6 @@ featureset_ptr gdal_datasource::features_at_point(coord2d const& pt, double tol)
                                               dx_,
                                               dy_,
                                               nodata_value_,
-                                              nodata_tolerance_);
+                                              nodata_tolerance_,
+                                              max_image_area_);
 }

plugins/input/gdal/gdal_datasource.hpp

@@ -68,6 +68,7 @@ private:
     bool shared_dataset_;
     boost::optional<double> nodata_value_;
     double nodata_tolerance_;
+    int64_t max_image_area_;
 };
 
 #endif // GDAL_DATASOURCE_HPP

plugins/input/gdal/gdal_featureset.cpp

@@ -89,7 +89,8 @@ gdal_featureset::gdal_featureset(GDALDataset& dataset,
                                  double dx,
                                  double dy,
                                  boost::optional<double> const& nodata,
-                                 double nodata_tolerance)
+                                 double nodata_tolerance,
+                                 int64_t max_image_area)
     : dataset_(dataset),
       ctx_(std::make_shared<mapnik::context_type>()),
       band_(band),
@@ -102,6 +103,7 @@ gdal_featureset::gdal_featureset(GDALDataset& dataset,
       nbands_(nbands),
       nodata_value_(nodata),
       nodata_tolerance_(nodata_tolerance),
+      max_image_area_(max_image_area),
       first_(true)
 {
     ctx_->push("nodata");
@@ -280,16 +282,11 @@ feature_ptr gdal_featureset::get_feature(mapnik::query const& q)
         }
     }
     
-    // Maximum memory limitation for image will be simply based on the maximum
-    // area we allow for an image. The true memory footprint therefore will vary based
-    // on the type of imagery that exists. 
-    // max_im_area based on 50 mb limit for RGBA
-    constexpr int64_t max_im_area = (50*1024*1024) / 4;
     int64_t im_area = (int64_t)im_width * (int64_t)im_height;
-    if (im_area > max_im_area)
+    if (im_area > max_image_area_)
     {
-        int adjusted_width = static_cast<int>(std::round(std::sqrt(max_im_area * ((double)im_width / (double)im_height))));
+        int adjusted_width = static_cast<int>(std::round(std::sqrt(max_image_area_ * ((double)im_width / (double)im_height))));
-        int adjusted_height = static_cast<int>(std::round(std::sqrt(max_im_area * ((double)im_height / (double)im_width))));
+        int adjusted_height = static_cast<int>(std::round(std::sqrt(max_image_area_ * ((double)im_height / (double)im_width))));
         if (adjusted_width < 1)
         {
             adjusted_width = 1;

plugins/input/gdal/gdal_featureset.hpp

@@ -66,7 +66,8 @@ public:
                     double dx,
                     double dy,
                     boost::optional<double> const& nodata,
-                    double nodata_tolerance);
+                    double nodata_tolerance,
+                    int64_t max_image_area);
     virtual ~gdal_featureset();
     mapnik::feature_ptr next();
 
@@ -85,6 +86,7 @@ private:
     int nbands_;
     boost::optional<double> nodata_value_;
     double nodata_tolerance_;
+    int64_t max_image_area_;
     bool first_;
 };
 

test/data-visual

@@ -1 +1 @@
-Subproject commit 924e0bcf16a2607cc002517c1d4e98f67edcbd39
+Subproject commit 6ece97e8d43915527b4bd83507a9cd9ea9ef910e