further gdal nodata handling improvements - refs #2023

Conflicts:
	plugins/input/gdal/gdal_featureset.cpp

CHANGELOG.md

@@ -14,6 +14,12 @@ Released ...
 
 Summary: TODO
 
+- GDAL plugin: Added back support for user driven `nodata` on rgb(a) images (#2023)
+
+- GDAL plugin: Allowed nodata to override alpha band if set on rgba images (#2023)
+
+- GDAL plugin: Added `nodata_tolerance` option to set nearby pixels transparent (has similar effect to the `nearblack` program) (#2023)
+
 - Added support for web fonts: .woff format (#2113)
 
 - Added missing support for `geometry-transform` in `line-pattern` and `polygon-pattern` symbolizers (#2065)

plugins/input/gdal/gdal_datasource.cpp

@@ -77,7 +77,8 @@ inline GDALDataset* gdal_datasource::open_dataset() const
 gdal_datasource::gdal_datasource(parameters const& params)
     : datasource(params),
       desc_(*params.get<std::string>("type"), "utf-8"),
-      nodata_value_(params.get<double>("nodata"))
+      nodata_value_(params.get<double>("nodata")),
+      nodata_tolerance_(*params.get<double>("nodata_tolerance",1e-12))
 {
     MAPNIK_LOG_DEBUG(gdal) << "gdal_datasource: Initializing...";
 
@@ -132,16 +133,28 @@ gdal_datasource::gdal_datasource(parameters const& params)
         tr[3] = extent_.maxy();
         tr[4] = 0;
         tr[5] = -extent_.height() / (double)height_;
+        MAPNIK_LOG_DEBUG(gdal) << "gdal_datasource extent override gives Geotransform="
+                               << tr[0] << "," << tr[1] << ","
+                               << tr[2] << "," << tr[3] << ","
+                               << tr[4] << "," << tr[5];
     }
     else
     {
-        dataset->GetGeoTransform(tr);
+        if (dataset->GetGeoTransform(tr) != CPLE_None)
+        {
+            MAPNIK_LOG_DEBUG(gdal) << "gdal_datasource GetGeotransform failure gives="
+                                   << tr[0] << "," << tr[1] << ","
+                                   << tr[2] << "," << tr[3] << ","
+                                   << tr[4] << "," << tr[5];
         }
-
+        else
+        {
             MAPNIK_LOG_DEBUG(gdal) << "gdal_datasource Geotransform="
                                    << tr[0] << "," << tr[1] << ","
                                    << tr[2] << "," << tr[3] << ","
                                    << tr[4] << "," << tr[5];
+        }
+    }
 
     // TODO - We should throw for true non-north up images, but the check
     // below is clearly too restrictive.
@@ -228,7 +241,8 @@ featureset_ptr gdal_datasource::features(query const& q) const
                                               nbands_,
                                               dx_,
                                               dy_,
-                                              nodata_value_));
+                                              nodata_value_,
+                                              nodata_tolerance_));
 }
 
 featureset_ptr gdal_datasource::features_at_point(coord2d const& pt, double tol) const
@@ -249,5 +263,6 @@ featureset_ptr gdal_datasource::features_at_point(coord2d const& pt, double tol)
                                               nbands_,
                                               dx_,
                                               dy_,
-                                              nodata_value_));
+                                              nodata_value_,
+                                              nodata_tolerance_));
 }

plugins/input/gdal/gdal_datasource.hpp

@@ -67,6 +67,7 @@ private:
     int nbands_;
     bool shared_dataset_;
     boost::optional<double> nodata_value_;
+    double nodata_tolerance_;
 };
 
 #endif // GDAL_DATASOURCE_HPP

plugins/input/gdal/gdal_featureset.cpp

@@ -34,6 +34,7 @@
 #include <boost/variant/apply_visitor.hpp>
 // stl
 #include <cmath>
+#include <memory>
 
 #include "gdal_featureset.hpp"
 #include <gdal_priv.h>
@@ -60,7 +61,8 @@ gdal_featureset::gdal_featureset(GDALDataset& dataset,
                                  int nbands,
                                  double dx,
                                  double dy,
-                                 boost::optional<double> const& nodata)
+                                 boost::optional<double> const& nodata,
+                                 double nodata_tolerance)
     : dataset_(dataset),
       ctx_(std::make_shared<mapnik::context_type>()),
       band_(band),
@@ -72,6 +74,7 @@ gdal_featureset::gdal_featureset(GDALDataset& dataset,
       dy_(dy),
       nbands_(nbands),
       nodata_value_(nodata),
+      nodata_tolerance_(nodata_tolerance),
       first_(true)
 {
     ctx_->push("nodata");
@@ -185,9 +188,9 @@ feature_ptr gdal_featureset::get_feature(mapnik::query const& q)
         int im_width = int(width_res * intersect.width() + 0.5);
         int im_height = int(height_res * intersect.height() + 0.5);
 
-        double sym_downsample_factor = q.get_filter_factor();
+        double filter_factor = q.get_filter_factor();
-        im_width = int(im_width * sym_downsample_factor + 0.5);
+        im_width = int(im_width * filter_factor + 0.5);
-        im_height = int(im_height * sym_downsample_factor + 0.5);
+        im_height = int(im_height * filter_factor + 0.5);
 
         // case where we need to avoid upsampling so that the
         // image can be later scaled within raster_symbolizer
@@ -287,13 +290,13 @@ feature_ptr gdal_featureset::get_feature(mapnik::query const& q)
                     MAPNIK_LOG_DEBUG(gdal) << "gdal_featureset: Processing rgb bands...";
                     raster_nodata = red->GetNoDataValue(&raster_has_nodata);
                     GDALColorTable *color_table = red->GetColorTable();
-                    if (!alpha && raster_has_nodata && !color_table)
+                    bool has_nodata = nodata_value_ || raster_has_nodata;
+                    if (has_nodata && !color_table)
                     {
+                        double apply_nodata = nodata_value_ ? *nodata_value_ : raster_nodata;
                         // read the data in and create an alpha channel from the nodata values
-                        // NOTE: we intentionally ignore user supplied nodata value since it only
+                        // TODO - we assume here the nodata value for the red band applies to all bands
-                        // works for grayscale images or a single band (as a double)
+                        // more details about this at http://trac.osgeo.org/gdal/ticket/2734
-                        // TODO - we assume here the nodata value for the red band applies to all band
-                        // but that may not always be the case: http://trac.osgeo.org/gdal/ticket/2734
                         float* imageData = (float*)image.getBytes();
                         red->RasterIO(GF_Read, x_off, y_off, width, height,
                                       imageData, image.width(), image.height(),
@@ -301,7 +304,7 @@ feature_ptr gdal_featureset::get_feature(mapnik::query const& q)
                         int len = image.width() * image.height();
                         for (int i = 0; i < len; ++i)
                         {
-                            if (std::fabs(raster_nodata - imageData[i]) < 1e-12)
+                            if (std::fabs(apply_nodata - imageData[i]) < nodata_tolerance_)
                             {
                                 *reinterpret_cast<unsigned *>(&imageData[i]) = 0;
                             }
@@ -336,7 +339,7 @@ feature_ptr gdal_featureset::get_feature(mapnik::query const& q)
                         int len = image.width() * image.height();
                         for (int i = 0; i < len; ++i)
                         {
-                            if (std::fabs(apply_nodata - imageData[i]) < 1e-12)
+                            if (std::fabs(apply_nodata - imageData[i]) < nodata_tolerance_)
                             {
                                 *reinterpret_cast<unsigned *>(&imageData[i]) = 0;
                             }
@@ -380,13 +383,16 @@ feature_ptr gdal_featureset::get_feature(mapnik::query const& q)
                 if (alpha)
                 {
                     MAPNIK_LOG_DEBUG(gdal) << "gdal_featureset: processing alpha band...";
-                    if (raster_has_nodata)
+                    if (!raster_has_nodata)
                     {
-                        MAPNIK_LOG_ERROR(gdal) << "warning: alpha channel being used instead of nodata value";
-                    }
                         alpha->RasterIO(GF_Read, x_off, y_off, width, height, image.getBytes() + 3,
                                         image.width(), image.height(), GDT_Byte, 4, 4 * image.width());
                     }
+                    else
+                    {
+                        MAPNIK_LOG_ERROR(gdal) << "warning: nodata value (" << raster_nodata << ") used to set transparency instead of alpha band";
+                    }
+                }
             }
             // set nodata value to be used in raster colorizer
             if (nodata_value_)

plugins/input/gdal/gdal_featureset.hpp

@@ -67,7 +67,8 @@ public:
                     int nbands,
                     double dx,
                     double dy,
-                    boost::optional<double> const& nodata);
+                    boost::optional<double> const& nodata,
+                    double nodata_tolerance);
     virtual ~gdal_featureset();
     mapnik::feature_ptr next();
 
@@ -90,6 +91,7 @@ private:
     double dy_;
     int nbands_;
     boost::optional<double> nodata_value_;
+    double nodata_tolerance_;
     bool first_;
 };