QgsRasterProjector::destExtentSize - calc destination extent and size from source

blazek · blazek · commit ece9a92d4cab · 2015-05-16T12:59:54.000+02:00
diff --git a/src/core/raster/qgsrasterprojector.cpp b/src/core/raster/qgsrasterprojector.cpp
@@ -14,6 +14,7 @@
  *   (at your option) any later version.                                   *
  *                                                                         *
  ***************************************************************************/
+#include <algorithm>
 
 #include "qgsrasterdataprovider.h"
 #include "qgscrscache.h"
@@ -941,3 +942,27 @@ QgsRasterBlock * QgsRasterProjector::block( int bandNo, QgsRectangle  const & ex
 
   return outputBlock;
 }
+
+bool QgsRasterProjector::destExtentSize( const QgsRectangle& theSrcExtent, int theSrcXSize, int theSrcYSize,
+    QgsRectangle& theDestExtent, int& theDestXSize, int& theDesYSize )
+{
+  if ( theSrcExtent.isEmpty() || theSrcXSize <= 0 || theSrcYSize <= 0 )
+  {
+    return false;
+  }
+  QgsCoordinateTransform ct( mSrcCRS, mDestCRS );
+  theDestExtent = ct.transformBoundingBox( theSrcExtent );
+
+  // We reproject pixel rectangle from center of source, of course, it gives
+  // bigger xRes,yRes than reprojected edges (envelope), it may also be that
+  // close to margins are higher resolutions (even very, too high)
+  // TODO: consider more precise resolution calculation
+  double xRes = theSrcExtent.width() / theSrcXSize;
+  double yRes = theSrcExtent.height() / theSrcYSize;
+  QgsPoint srcCenter = theSrcExtent.center();
+  QgsRectangle srcCenterRectangle( srcCenter.x() - xRes / 2, srcCenter.y() - yRes / 2, srcCenter.x() + xRes / 2, srcCenter.y() + yRes / 2 );
+  QgsRectangle destCenterRectangle =  ct.transformBoundingBox( srcCenterRectangle );
+  theDestXSize = std::max( 1, ( int )( theDestExtent.width() / destCenterRectangle.width() ) );
+  theDesYSize = std::max( 1, ( int )( theDestExtent.height() / destCenterRectangle.height() ) );
+  return true;
+}
diff --git a/src/core/raster/qgsrasterprojector.h b/src/core/raster/qgsrasterprojector.h
@@ -103,6 +103,11 @@ class CORE_EXPORT QgsRasterProjector : public QgsRasterInterface
 
     QgsRasterBlock *block( int bandNo, const QgsRectangle & extent, int width, int height ) override;
 
+    /** Calculate destination extent and size from source extent and size
+     */
+    bool destExtentSize( const QgsRectangle& theSrcExtent, int theSrcXSize, int theSrcYSize,
+                         QgsRectangle& theDestExtent, int& theDestXSize, int& theDesYSize );
+
   private:
     /** get source extent */
     QgsRectangle srcExtent() { return mSrcExtent; }
