Added class QgsRasterIterator

qgis · Jul 7, 2012 · 3f1056a · 3f1056a
1 parent 2b53f49
commit 3f1056a
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diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
@@ -161,6 +161,7 @@ SET(QGIS_CORE_SRCS
   raster/qgslinearminmaxenhancementwithclip.cpp
   raster/qgspseudocolorshader.cpp
   raster/qgsrasterinterface.cpp
+  raster/qgsrasteriterator.cpp
   raster/qgsrasterlayer.cpp
   raster/qgsrastertransparency.cpp
   raster/qgsrasterpipe.cpp

diff --git a/src/core/raster/qgsrasteriterator.cpp b/src/core/raster/qgsrasteriterator.cpp
@@ -0,0 +1,127 @@
+#include "qgsrasteriterator.h"
+#include "qgsrasterinterface.h"
+#include "qgsrasterprojector.h"
+#include "qgsrasterviewport.h"
+
+QgsRasterIterator::QgsRasterIterator( QgsRasterInterface* input ): mInput( input )
+{
+}
+
+QgsRasterIterator::~QgsRasterIterator()
+{
+}
+
+void QgsRasterIterator::startRasterRead( int bandNumber, QgsRasterViewPort* viewPort, const QgsMapToPixel* mapToPixel )
+{
+  if ( !viewPort || !mapToPixel || !mInput )
+  {
+    return;
+  }
+
+  //remove any previous part on that band
+  removePartInfo( bandNumber );
+
+  //split raster into small portions if necessary
+  RasterPartInfo pInfo;
+  pInfo.nCols = viewPort->drawableAreaXDim;
+  pInfo.nRows = viewPort->drawableAreaYDim;
+
+  //effective oversampling factors are different to global one because of rounding
+  //oversamplingX = (( double )pInfo.nCols * oversampling ) / viewPort->drawableAreaXDim;
+  //oversamplingY = (( double )pInfo.nRows * oversampling ) / viewPort->drawableAreaYDim;
+
+  // TODO : we dont know oversampling (grid size) here - how to get totalMemoryUsage ?
+  //int totalMemoryUsage = pInfo.nCols * oversamplingX * pInfo.nRows * oversamplingY * mInput->dataTypeSize( bandNumber );
+  int totalMemoryUsage = pInfo.nCols * pInfo.nRows * mInput->dataTypeSize( bandNumber );
+  int parts = totalMemoryUsage / 100000000 + 1;
+  int nPartsPerDimension = sqrt( parts );
+  pInfo.nColsPerPart = pInfo.nCols / nPartsPerDimension;
+  pInfo.nRowsPerPart = pInfo.nRows / nPartsPerDimension;
+  pInfo.currentCol = 0;
+  pInfo.currentRow = 0;
+  pInfo.data = 0;
+  pInfo.prj = 0;
+  mRasterPartInfos.insert( bandNumber, pInfo );
+}
+
+bool QgsRasterIterator::readNextRasterPart( int bandNumber, QgsRasterViewPort* viewPort,
+    int& nCols, int& nRows,
+    void** rasterData,
+    int& topLeftCol, int& topLeftRow )
+{
+  if ( !viewPort )
+  {
+    return false;
+  }
+
+  //get partinfo
+  QMap<int, RasterPartInfo>::iterator partIt = mRasterPartInfos.find( bandNumber );
+  if ( partIt == mRasterPartInfos.end() )
+  {
+    return false;
+  }
+
+  RasterPartInfo& pInfo = partIt.value();
+
+  //remove last data block
+  // TODO: data are released somewhere else (check)
+  //free( pInfo.data );
+  pInfo.data = 0;
+  delete pInfo.prj;
+  pInfo.prj = 0;
+
+  //already at end
+  if ( pInfo.currentCol == pInfo.nCols && pInfo.currentRow == pInfo.nRows )
+  {
+    return false;
+  }
+
+  //read data block
+  nCols = qMin( pInfo.nColsPerPart, pInfo.nCols - pInfo.currentCol );
+  nRows = qMin( pInfo.nRowsPerPart, pInfo.nRows - pInfo.currentRow );
+
+  //get subrectangle
+  QgsRectangle viewPortExtent = viewPort->mDrawnExtent;
+  double xmin = viewPortExtent.xMinimum() + pInfo.currentCol / ( double )pInfo.nCols * viewPortExtent.width();
+  double xmax = viewPortExtent.xMinimum() + ( pInfo.currentCol + nCols ) / ( double )pInfo.nCols * viewPortExtent.width();
+  double ymin = viewPortExtent.yMaximum() - ( pInfo.currentRow + nRows ) / ( double )pInfo.nRows * viewPortExtent.height();
+  double ymax = viewPortExtent.yMaximum() - pInfo.currentRow / ( double )pInfo.nRows * viewPortExtent.height();
+  QgsRectangle blockRect( xmin, ymin, xmax, ymax );
+
+  pInfo.data = mInput->block( bandNumber, blockRect, nCols, nRows );
+
+  *rasterData = pInfo.data;
+  topLeftCol = pInfo.currentCol;
+  topLeftRow = pInfo.currentRow;
+
+  pInfo.currentCol += nCols;
+  if ( pInfo.currentCol == pInfo.nCols && pInfo.currentRow + nRows == pInfo.nRows ) //end of raster
+  {
+    pInfo.currentRow = pInfo.nRows;
+  }
+  else if ( pInfo.currentCol == pInfo.nCols ) //start new row
+  {
+    pInfo.currentCol = 0;
+    pInfo.currentRow += pInfo.nRowsPerPart;
+  }
+
+  return true;
+}
+
+void QgsRasterIterator::stopRasterRead( int bandNumber )
+{
+  removePartInfo( bandNumber );
+}
+
+void QgsRasterIterator::removePartInfo( int bandNumber )
+{
+  QMap<int, RasterPartInfo>::iterator partIt = mRasterPartInfos.find( bandNumber );
+  if ( partIt != mRasterPartInfos.end() )
+  {
+    RasterPartInfo& pInfo = partIt.value();
+    //CPLFree( pInfo.data );
+    free( pInfo.data );
+    delete pInfo.prj;
+    mRasterPartInfos.remove( bandNumber );
+  }
+}
diff --git a/src/core/raster/qgsrasteriterator.h b/src/core/raster/qgsrasteriterator.h
@@ -0,0 +1,56 @@
+#ifndef QGSRASTERITERATOR_H
+#define QGSRASTERITERATOR_H
+
+#include <QMap>
+
+class QgsMapToPixel;
+class QgsRasterInterface;
+class QgsRasterProjector;
+class QgsRasterViewPort;
+
+class QgsRasterIterator
+{
+  public:
+    //Stores information about reading of a raster band. Columns and rows are in unsampled coordinates
+    struct RasterPartInfo
+    {
+      int currentCol;
+      int currentRow;
+      int nCols;
+      int nRows;
+      int nColsPerPart;
+      int nRowsPerPart;
+      void* data; //data (can be in oversampled/undersampled resolution)
+      QgsRasterProjector* prj; //raster projector (or 0 if no reprojection is done)
+    };
+
+    QgsRasterIterator( QgsRasterInterface* input );
+    ~QgsRasterIterator();
+
+    /**Start reading of raster band. Raster data can then be retrieved by calling readNextRasterPart until it returns false.
+      @param bandNumer number of raster band to read
+      @param viewPort describes raster position on screen
+     */
+    void startRasterRead( int bandNumber, QgsRasterViewPort* viewPort, const QgsMapToPixel* mapToPixel );
+
+    /**Fetches next part of raster data
+       @param nCols number of columns on output device
+       @param nRows number of rows on output device
+       @param nColsRaster number of raster columns (different to nCols if oversamplingX != 1.0)
+       @param nRowsRaster number of raster rows (different to nRows if oversamplingY != 0)*/
+    bool readNextRasterPart( int bandNumber, QgsRasterViewPort* viewPort,
+                             int& nCols, int& nRows,
+                             void** rasterData,
+                             int& topLeftCol, int& topLeftRow );
+
+    void stopRasterRead( int bandNumber );
+
+  private:
+    QgsRasterInterface* mInput;
+    QMap<int, RasterPartInfo> mRasterPartInfos;
+
+    /**Remove part into and release memory*/
+    void removePartInfo( int bandNumber );
+};
+
+#endif // QGSRASTERITERATOR_H