gdal identify with 2x2 block, hopefully fix for #4594 (slow identify …

…with ecw
qgis · Aug 22, 2012 · a795a5d · a795a5d
1 parent a2b6bcc
commit a795a5d
Showing 1 changed file with 23 additions and 57 deletions.
diff --git a/src/providers/gdal/qgsgdalprovider.cpp b/src/providers/gdal/qgsgdalprovider.cpp
@@ -844,15 +844,31 @@ bool QgsGdalProvider::identify( const QgsPoint & point, QMap<int, QString>& resu
     for ( int i = 1; i <= GDALGetRasterCount( mGdalDataset ); i++ )
     {
       GDALRasterBandH gdalBand = GDALGetRasterBand( mGdalDataset, i );
-      double value;
+      double data[4];
 
-      CPLErr err = GDALRasterIO( gdalBand, GF_Read, col, row, 1, 1,
-                                 &value, 1, 1, GDT_Float64, 0, 0 );
+      // GDAL ECW driver reads whole row if single pixel (nYSize == 1) is requested
+      // and it makes identify very slow -> use 2x2 matrix
+      int r = 0;
+      int c = 0;
+      if ( col == mWidth - 1 && mWidth > 1 )
+      {
+        col--;
+        c++;
+      }
+      if ( row == mHeight - 1 && mHeight > 1 )
+      {
+        row--;
+        r++;
+      }
+
+      CPLErr err = GDALRasterIO( gdalBand, GF_Read, col, row, 2, 2,
+                                 data, 2, 2, GDT_Float64, 0, 0 );
 
       if ( err != CPLE_None )
       {
         QgsLogger::warning( "RasterIO error: " + QString::fromUtf8( CPLGetLastErrorMsg() ) );
       }
+      double value = data[r*2+c];
 
       //double value = readValue( data, type, 0 );
       // QgsDebugMsg( QString( "value=%1" ).arg( value ) );
@@ -878,62 +894,12 @@ bool QgsGdalProvider::identify( const QgsPoint & point, QMap<int, QString>& resu
 
 bool QgsGdalProvider::identify( const QgsPoint& thePoint, QMap<QString, QString>& theResults )
 {
-  // QgsDebugMsg( "Entered" );
-  if ( !mExtent.contains( thePoint ) )
+  QMap<int, QString> results;
+  identify( thePoint, results );
+  for ( int i = 1; i <= GDALGetRasterCount( mGdalDataset ); i++ )
   {
-    // Outside the raster
-    for ( int i = 1; i <= GDALGetRasterCount( mGdalDataset ); i++ )
-    {
-      theResults[ generateBandName( i )] = tr( "out of extent" );
-    }
+    theResults[ generateBandName( i )] = results.value( i );
   }
-  else
-  {
-    double x = thePoint.x();
-    double y = thePoint.y();
-
-    // Calculate the row / column where the point falls
-    double xres = ( mExtent.xMaximum() - mExtent.xMinimum() ) / mWidth;
-    double yres = ( mExtent.yMaximum() - mExtent.yMinimum() ) / mHeight;
-
-    // Offset, not the cell index -> flor
-    int col = ( int ) floor(( x - mExtent.xMinimum() ) / xres );
-    int row = ( int ) floor(( mExtent.yMaximum() - y ) / yres );
-
-    // QgsDebugMsg( "row = " + QString::number( row ) + " col = " + QString::number( col ) );
-
-    for ( int i = 1; i <= GDALGetRasterCount( mGdalDataset ); i++ )
-    {
-      GDALRasterBandH gdalBand = GDALGetRasterBand( mGdalDataset, i );
-      double value;
-
-      CPLErr err = GDALRasterIO( gdalBand, GF_Read, col, row, 1, 1,
-                                 &value, 1, 1, GDT_Float64, 0, 0 );
-
-      if ( err != CPLE_None )
-      {
-        QgsLogger::warning( "RasterIO error: " + QString::fromUtf8( CPLGetLastErrorMsg() ) );
-      }
-
-      //double value = readValue( data, type, 0 );
-      // QgsDebugMsg( QString( "value=%1" ).arg( value ) );
-      QString v;
-
-      if ( mValidNoDataValue && ( fabs( value - mNoDataValue[i-1] ) <= TINY_VALUE || value != value ) )
-      {
-        v = tr( "null (no data)" );
-      }
-      else
-      {
-        v.setNum( value );
-      }
-
-      theResults[ generateBandName( i )] = v;
-
-      //CPLFree( data );
-    }
-  }
-
   return true;
 }