Add error messages, fix reporting of grid offset

python/analysis/raster/qgsalignraster.sip

@@ -132,6 +132,10 @@ class QgsAlignRaster
     //! @return true on success
     bool run();
 
+    //! Return error from a previous run() call.
+    //! Error message is empty if run() succeeded (returned true)
+    QString errorMessage() const;
+
     //! write contents of the object to standard error stream - for debugging
     void dump() const;
 

src/analysis/raster/qgsalignraster.cpp

@@ -42,6 +42,11 @@ static double floor_with_tolerance( double value )
     return qFloor( value );
 }
 
+static double fmod_with_tolerance( double num, double denom )
+{
+  return num - floor_with_tolerance( num / denom ) * denom;
+}
+
 
 static QgsRectangle transform_to_extent( const double* geotransform, double xSize, double ySize )
 {
@@ -173,7 +178,13 @@ bool QgsAlignRaster::determineTransformAndSize()
     // handle (setting it to NULL).
     void* hTransformArg = GDALCreateGenImgProjTransformer( info.mDataset, info.mCrsWkt.constData(), NULL, mCrsWkt.constData(), FALSE, 0, 1 );
     if ( !hTransformArg )
+    {
+      mErrorMessage = QString( "GDALCreateGenImgProjTransformer failed.\n\n"
+                               "Source WKT:\n%1\n\nDestination WKT:\n%2" )
+                      .arg( QString::fromAscii( info.mCrsWkt ) )
+                      .arg( QString::fromAscii( mCrsWkt ) );
       return false;
+    }
 
     // Get approximate output georeferenced bounds and resolution for file.
     double adfDstGeoTransform[6];
@@ -187,7 +198,10 @@ bool QgsAlignRaster::determineTransformAndSize()
     r.srcCellSizeInDestCRS = fabs( adfDstGeoTransform[1] * adfDstGeoTransform[5] );
 
     if ( eErr != CE_None )
+    {
+      mErrorMessage = QString( "GDALSuggestedWarpOutput2 failed.\n\n" + r.inputFilename );
       return false;
+    }
 
     if ( finalExtent[0] == 0 && finalExtent[1] == 0 && finalExtent[2] == 0 && finalExtent[3] == 0 )
     {
@@ -234,7 +248,10 @@ bool QgsAlignRaster::determineTransformAndSize()
   mYSize = floor_with_tolerance(( finalExtent[3] - originY ) / mCellSizeY );
 
   if ( mXSize <= 0 || mYSize <= 0 )
+  {
+    mErrorMessage = QObject::tr( "Configured inputs have no common intersecting area." );
     return false;
+  }
 
   // build final geotransform...
   mGeoTransform[0] = originX;
@@ -250,6 +267,8 @@ bool QgsAlignRaster::determineTransformAndSize()
 
 bool QgsAlignRaster::run()
 {
+  mErrorMessage.clear();
+
   // consider extent of all layers and setup geotransform and output grid size
   if ( !determineTransformAndSize() )
     return false;
@@ -283,12 +302,18 @@ bool QgsAlignRaster::createAndWarp( const Item& raster )
 {
   GDALDriverH hDriver = GDALGetDriverByName( "GTiff" );
   if ( !hDriver )
+  {
+    mErrorMessage = QString( "GDALGetDriverByName(GTiff) failed." );
     return false;
+  }
 
   // Open the source file.
   GDALDatasetH hSrcDS = GDALOpen( raster.inputFilename.toLocal8Bit().constData(), GA_ReadOnly );
   if ( !hSrcDS )
+  {
+    mErrorMessage = QObject::tr( "Unable to open input file: " ) + raster.inputFilename;
     return false;
+  }
 
   // Create output with same datatype as first input band.
 
@@ -302,6 +327,7 @@ bool QgsAlignRaster::createAndWarp( const Item& raster )
   if ( !hDstDS )
   {
     GDALClose( hSrcDS );
+    mErrorMessage = QObject::tr( "Unable to create output file: " ) + raster.outputFilename;
     return false;
   }
 
@@ -401,8 +427,8 @@ QSizeF QgsAlignRaster::RasterInfo::cellSize() const
 
 QPointF QgsAlignRaster::RasterInfo::gridOffset() const
 {
-  return QPointF( fmod( mGeoTransform[0], cellSize().width() ),
-                  fmod( mGeoTransform[3], cellSize().height() ) );
+  return QPointF( fmod_with_tolerance( mGeoTransform[0], cellSize().width() ),
+                  fmod_with_tolerance( mGeoTransform[3], cellSize().height() ) );
 }
 
 QgsRectangle QgsAlignRaster::RasterInfo::extent() const

src/analysis/raster/qgsalignraster.h

@@ -178,6 +178,10 @@ class ANALYSIS_EXPORT QgsAlignRaster
     //! @return true on success
     bool run();
 
+    //! Return error from a previous run() call.
+    //! Error message is empty if run() succeeded (returned true)
+    QString errorMessage() const { return mErrorMessage; }
+
     //! write contents of the object to standard error stream - for debugging
     void dump() const;
 
@@ -196,6 +200,9 @@ class ANALYSIS_EXPORT QgsAlignRaster
     //! Object that facilitates reporting of progress / cancellation
     ProgressHandler* mProgressHandler;
 
+    //! Last error message from run()
+    QString mErrorMessage;
+
     //! List of rasters to be aligned (with their output files and other options)
     List mRasters;
 

src/app/qgsalignrasterdialog.cpp

@@ -157,6 +157,7 @@ void QgsAlignRasterDialog::editLayer()
   itemNew.resampleMethod = ( QgsAlignRaster::ResampleAlg ) d.resampleMethod();
   itemNew.rescaleValues = d.rescaleValues();
   list[current.row()] = itemNew;
+  mAlign->setRasters( list );
 
   populateLayersView();
 }
@@ -207,8 +208,7 @@ void QgsAlignRasterDialog::runAlign()
   }
   else
   {
-    // TODO: error message with reason
-    QMessageBox::critical( this, tr( "Align Rasters" ), tr( "Failed to align rasters." ) );
+    QMessageBox::critical( this, tr( "Align Rasters" ), tr( "Failed to align rasters:" ) + "\n\n" + mAlign->errorMessage() );
   }
 }
 

tests/src/analysis/testqgsalignraster.cpp

@@ -16,6 +16,7 @@
 #include <QtTest/QtTest>
 
 #include "qgsalignraster.h"
+#include "qgsrectangle.h"
 
 #include <QDir>
 
@@ -43,6 +44,15 @@ class TestAlignRaster : public QObject
       SRC_FILE = QString( TEST_DATA_DIR ) + QDir::separator() + "float1-16.tif";
     }
 
+    void testRasterInfo()
+    {
+      QgsAlignRaster::RasterInfo out( SRC_FILE );
+      QVERIFY( out.isValid() );
+      QCOMPARE( out.cellSize(), QSizeF( 0.2, 0.2 ) );
+      QCOMPARE( out.gridOffset(), QPointF( 0.0, 0.0 ) );
+      QCOMPARE( out.extent(), QgsRectangle( 106.0, -7.0, 106.8, -6.2 ) );
+    }
+
     void testClip()
     {
       QString tmpFile( _tempFile( "clip" ) );
@@ -159,9 +169,10 @@ class TestAlignRaster : public QObject
       align.setRasters( rasters );
       align.setParametersFromRaster( SRC_FILE );
       align.setCellSize( 0.4, 0.4 );
-      QPointF offset = align.gridOffset();
-      offset.rx() += 0.2;
-      align.setGridOffset( offset );
+      // a technicality: the raster's origin is at y=-7 so we need to shift the offset,
+      // because with zero Y offset the grid goes -6.8 ... -7.2 - with offset of 0.2
+      // the grid will start at -7  (with X axis no need for shift as 106 % 0.4 == 0)
+      align.setGridOffset( QPointF( 0.0, 0.2 ) );
       bool res = align.run();
       QVERIFY( res );
 
@@ -185,9 +196,10 @@ class TestAlignRaster : public QObject
       align.setRasters( rasters );
       align.setParametersFromRaster( SRC_FILE );
       align.setCellSize( 0.4, 0.4 );
-      QPointF offset = align.gridOffset();
-      offset.rx() += 0.2;
-      align.setGridOffset( offset );
+      // a technicality: the raster's origin is at y=-7 so we need to shift the offset,
+      // because with zero Y offset the grid goes -6.8 ... -7.2 - with offset of 0.2
+      // the grid will start at -7  (with X axis no need for shift as 106 % 0.4 == 0)
+      align.setGridOffset( QPointF( 0.0, 0.2 ) );
       bool res = align.run();
       QVERIFY( res );