QgsRasterBlock::data() for efficient access to pixel data also in Pyt…

…hon (#4009) Also adds some unit tests and API cleanups
qgis · Jan 18, 2017 · 433d04b · 433d04b
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diff --git a/doc/api_break.dox b/doc/api_break.dox
@@ -1469,6 +1469,12 @@ QgsRaster        {#qgis_api_break_3_0_QgsRaster}
 - QgsRaster::contrastEnhancementLimitsFromString() has been removed, use QgsRasterMinMaxOrigin::limitsFromString()
 
 
+QgsRasterBlock        {#qgis_api_break_3_0_QgsRasterBlock}
+--------------
+
+- The constructor and reset() do not take no data value as the fourth argument anymore. There is new call setNoDataValue() to set it.
+
+
 QgsRasterCalcNode        {#qgis_api_break_3_0_QgsRasterCalcNode}
 -----------------
 

diff --git a/python/core/raster/qgsrasterblock.sip b/python/core/raster/qgsrasterblock.sip
@@ -12,17 +12,8 @@ class QgsRasterBlock
      *  @param theDataType raster data type
      *  @param theWidth width of data matrix
      *  @param theHeight height of data matrix
-     *  @note not available in python bindings (use variant with theNoDataValue)
      */
-    // QgsRasterBlock( Qgis::DataType theDataType, int theWidth, int theHeight );
-
-    /** \brief Constructor which allocates data block in memory
-     *  @param theDataType raster data type
-     *  @param theWidth width of data matrix
-     *  @param theHeight height of data matrix
-     *  @param theNoDataValue the value representing no data (NULL)
-     */
-    QgsRasterBlock( Qgis::DataType theDataType, int theWidth, int theHeight, double theNoDataValue );
+    QgsRasterBlock( Qgis::DataType theDataType, int theWidth, int theHeight );
 
     virtual ~QgsRasterBlock();
 
@@ -31,18 +22,8 @@ class QgsRasterBlock
      *  @param theWidth width of data matrix
      *  @param theHeight height of data matrix
      *  @return true on success
-     *  @note not available in python bindings (use variant with theNoDataValue)
      */
-    // bool reset( Qgis::DataType theDataType, int theWidth, int theHeight );
-
-    /** \brief Reset block
-     *  @param theDataType raster data type
-     *  @param theWidth width of data matrix
-     *  @param theHeight height of data matrix
-     *  @param theNoDataValue the value representing no data (NULL)
-     *  @return true on success
-     */
-    bool reset( Qgis::DataType theDataType, int theWidth, int theHeight, double theNoDataValue );
+    bool reset( Qgis::DataType theDataType, int theWidth, int theHeight );
 
     // TODO: consider if use isValid() at all, isEmpty() should be sufficient
     // and works also if block is valid but empty - difference between valid and empty?
@@ -80,7 +61,9 @@ class QgsRasterBlock
     static Qgis::DataType typeWithNoDataValue( Qgis::DataType dataType, double *noDataValue );
 
     /** True if the block has no data value.
-     * @return true if the block has no data value */
+     * @return true if the block has no data value
+     * @see noDataValue(), setNoDataValue(), resetNoDataValue()
+     */
     bool hasNoDataValue() const;
 
     /** Returns true if the block may contain no data. It does not guarantee
@@ -89,9 +72,24 @@ class QgsRasterBlock
      * @return true if the block may contain no data */
     bool hasNoData() const;
 
+    /** Sets cell value that will be considered as "no data".
+     * @note added in QGIS 3.0
+     * @see noDataValue(), hasNoDataValue(), resetNoDataValue()
+     */
+    void setNoDataValue( double noDataValue );
+
+    /** Reset no data value: if there was a no data value previously set,
+     * it will be discarded.
+     * @note added in QGIS 3.0
+     * @see noDataValue(), hasNoDataValue(), setNoDataValue()
+     */
+    void resetNoDataValue();
+
     /** Return no data value. If the block does not have a no data value the
      *  returned value is undefined.
-     * @return No data value */
+     * @return No data value
+     * @see hasNoDataValue(), setNoDataValue(), resetNoDataValue()
+     */
     double noDataValue() const;
 
     /** Get byte array representing a value.
@@ -197,6 +195,16 @@ class QgsRasterBlock
      *  @note added in QGIS 2.10 */
     void setIsData( qgssize index );
 
+    /** Get access to raw data.
+     * The returned QByteArray instance is not a copy of the data: it only refers to the array
+     * owned by the QgsRasterBlock, therefore it is only valid while the QgsRasterBlock object
+     * still exists. Writing to the returned QByteArray will not affect the original data:
+     * a deep copy of the data will be made and only the local copy will be modified.
+     * @note in Python the method returns ordinary bytes object as the
+     * @note added in QGIS 3.0
+     */
+    QByteArray data() const;
+
     /** \brief Get pointer to data
      *  @param row row index
      *  @param column column index

diff --git a/src/core/raster/qgsrasterblock.cpp b/src/core/raster/qgsrasterblock.cpp
@@ -60,23 +60,6 @@ QgsRasterBlock::QgsRasterBlock( Qgis::DataType theDataType, int theWidth, int th
   ( void )reset( mDataType, mWidth, mHeight );
 }
 
-QgsRasterBlock::QgsRasterBlock( Qgis::DataType theDataType, int theWidth, int theHeight, double theNoDataValue )
-    : mValid( true )
-    , mDataType( theDataType )
-    , mTypeSize( 0 )
-    , mWidth( theWidth )
-    , mHeight( theHeight )
-    , mHasNoDataValue( true )
-    , mNoDataValue( theNoDataValue )
-    , mData( nullptr )
-    , mImage( nullptr )
-    , mNoDataBitmap( nullptr )
-    , mNoDataBitmapWidth( 0 )
-    , mNoDataBitmapSize( 0 )
-{
-  ( void )reset( mDataType, mWidth, mHeight, mNoDataValue );
-}
-
 QgsRasterBlock::~QgsRasterBlock()
 {
   QgsDebugMsgLevel( QString( "mData = %1" ).arg( reinterpret_cast< ulong >( mData ) ), 4 );
@@ -88,18 +71,6 @@ QgsRasterBlock::~QgsRasterBlock()
 bool QgsRasterBlock::reset( Qgis::DataType theDataType, int theWidth, int theHeight )
 {
   QgsDebugMsgLevel( QString( "theWidth= %1 theHeight = %2 theDataType = %3" ).arg( theWidth ).arg( theHeight ).arg( theDataType ), 4 );
-  if ( !reset( theDataType, theWidth, theHeight, std::numeric_limits<double>::quiet_NaN() ) )
-  {
-    return false;
-  }
-  mHasNoDataValue = false;
-  // the mNoDataBitmap is created only if necessary (usually, it is not) in setIsNoData()
-  return true;
-}
-
-bool QgsRasterBlock::reset( Qgis::DataType theDataType, int theWidth, int theHeight, double theNoDataValue )
-{
-  QgsDebugMsgLevel( QString( "theWidth= %1 theHeight = %2 theDataType = %3 theNoDataValue = %4" ).arg( theWidth ).arg( theHeight ).arg( theDataType ).arg( theNoDataValue ), 4 );
 
   qgsFree( mData );
   mData = nullptr;
@@ -144,8 +115,6 @@ bool QgsRasterBlock::reset( Qgis::DataType theDataType, int theWidth, int theHei
   mTypeSize = QgsRasterBlock::typeSize( mDataType );
   mWidth = theWidth;
   mHeight = theHeight;
-  mHasNoDataValue = true;
-  mNoDataValue = theNoDataValue;
   QgsDebugMsgLevel( QString( "mWidth= %1 mHeight = %2 mDataType = %3 mData = %4 mImage = %5" ).arg( mWidth ).arg( mHeight ).arg( mDataType )
                     .arg( reinterpret_cast< ulong >( mData ) ).arg( reinterpret_cast< ulong >( mImage ) ), 4 );
   return true;
@@ -278,6 +247,18 @@ bool QgsRasterBlock::hasNoData() const
   return mHasNoDataValue || mNoDataBitmap;
 }
 
+void QgsRasterBlock::setNoDataValue( double noDataValue )
+{
+  mHasNoDataValue = true;
+  mNoDataValue = noDataValue;
+}
+
+void QgsRasterBlock::resetNoDataValue()
+{
+  mHasNoDataValue = false;
+  mNoDataValue = std::numeric_limits<double>::quiet_NaN();
+}
+
 bool QgsRasterBlock::isNoDataValue( double value, double noDataValue )
 {
   // TODO: optimize no data value test by memcmp()
@@ -662,6 +643,16 @@ void QgsRasterBlock::setIsData( qgssize index )
   mNoDataBitmap[byte] = mNoDataBitmap[byte] & ~nodata;
 }
 
+QByteArray QgsRasterBlock::data() const
+{
+  if ( mData )
+    return QByteArray::fromRawData( static_cast<const char*>( mData ), typeSize( mDataType ) * mWidth * mHeight );
+  else if ( mImage && mImage->constBits() )
+    return QByteArray::fromRawData( reinterpret_cast<const char*>( mImage->constBits() ), mImage->byteCount() );
+  else
+    return QByteArray();
+}
+
 char * QgsRasterBlock::bits( qgssize index )
 {
   // Not testing type to avoid too much overhead because this method is called per pixel

diff --git a/src/core/raster/qgsrasterblock.h b/src/core/raster/qgsrasterblock.h
@@ -40,38 +40,19 @@ class CORE_EXPORT QgsRasterBlock
      *  @param theDataType raster data type
      *  @param theWidth width of data matrix
      *  @param theHeight height of data matrix
-     *  @note not available in python bindings (use variant with theNoDataValue)
      */
     QgsRasterBlock( Qgis::DataType theDataType, int theWidth, int theHeight );
 
-    /** \brief Constructor which allocates data block in memory
-     *  @param theDataType raster data type
-     *  @param theWidth width of data matrix
-     *  @param theHeight height of data matrix
-     *  @param theNoDataValue the value representing no data (NULL)
-     */
-    QgsRasterBlock( Qgis::DataType theDataType, int theWidth, int theHeight, double theNoDataValue );
-
     virtual ~QgsRasterBlock();
 
     /** \brief Reset block
      *  @param theDataType raster data type
      *  @param theWidth width of data matrix
      *  @param theHeight height of data matrix
      *  @return true on success
-     *  @note not available in python bindings (use variant with theNoDataValue)
      */
     bool reset( Qgis::DataType theDataType, int theWidth, int theHeight );
 
-    /** \brief Reset block
-     *  @param theDataType raster data type
-     *  @param theWidth width of data matrix
-     *  @param theHeight height of data matrix
-     *  @param theNoDataValue the value representing no data (NULL)
-     *  @return true on success
-     */
-    bool reset( Qgis::DataType theDataType, int theWidth, int theHeight, double theNoDataValue );
-
     // TODO: consider if use isValid() at all, isEmpty() should be sufficient
     // and works also if block is valid but empty - difference between valid and empty?
 
@@ -145,7 +126,9 @@ class CORE_EXPORT QgsRasterBlock
     static Qgis::DataType typeWithNoDataValue( Qgis::DataType dataType, double *noDataValue );
 
     /** True if the block has no data value.
-     * @return true if the block has no data value */
+     * @return true if the block has no data value
+     * @see noDataValue(), setNoDataValue(), resetNoDataValue()
+     */
     bool hasNoDataValue() const { return mHasNoDataValue; }
 
     /** Returns true if the block may contain no data. It does not guarantee
@@ -154,9 +137,24 @@ class CORE_EXPORT QgsRasterBlock
      * @return true if the block may contain no data */
     bool hasNoData() const;
 
+    /** Sets cell value that will be considered as "no data".
+     * @note added in QGIS 3.0
+     * @see noDataValue(), hasNoDataValue(), resetNoDataValue()
+     */
+    void setNoDataValue( double noDataValue );
+
+    /** Reset no data value: if there was a no data value previously set,
+     * it will be discarded.
+     * @note added in QGIS 3.0
+     * @see noDataValue(), hasNoDataValue(), setNoDataValue()
+     */
+    void resetNoDataValue();
+
     /** Return no data value. If the block does not have a no data value the
      *  returned value is undefined.
-     * @return No data value */
+     * @return No data value
+     * @see hasNoDataValue(), setNoDataValue(), resetNoDataValue()
+     */
     double noDataValue() const { return mNoDataValue; }
 
     /** Get byte array representing a value.
@@ -262,6 +260,16 @@ class CORE_EXPORT QgsRasterBlock
      *  @note added in QGIS 2.10 */
     void setIsData( qgssize index );
 
+    /** Get access to raw data.
+     * The returned QByteArray instance is not a copy of the data: it only refers to the array
+     * owned by the QgsRasterBlock, therefore it is only valid while the QgsRasterBlock object
+     * still exists. Writing to the returned QByteArray will not affect the original data:
+     * a deep copy of the data will be made and only the local copy will be modified.
+     * @note in Python the method returns ordinary bytes object as the
+     * @note added in QGIS 3.0
+     */
+    QByteArray data() const;
+
     /** \brief Get pointer to data
      *  @param row row index
      *  @param column column index

diff --git a/src/core/raster/qgsrasterdataprovider.cpp b/src/core/raster/qgsrasterdataprovider.cpp
@@ -48,14 +48,10 @@ QgsRasterBlock * QgsRasterDataProvider::block( int theBandNo, QgsRectangle  cons
   QgsDebugMsgLevel( QString( "theBandNo = %1 theWidth = %2 theHeight = %3" ).arg( theBandNo ).arg( theWidth ).arg( theHeight ), 4 );
   QgsDebugMsgLevel( QString( "theExtent = %1" ).arg( theExtent.toString() ), 4 );
 
-  QgsRasterBlock *block;
+  QgsRasterBlock *block = new QgsRasterBlock( dataType( theBandNo ), theWidth, theHeight );
   if ( sourceHasNoDataValue( theBandNo ) && useSourceNoDataValue( theBandNo ) )
   {
-    block = new QgsRasterBlock( dataType( theBandNo ), theWidth, theHeight, sourceNoDataValue( theBandNo ) );
-  }
-  else
-  {
-    block = new QgsRasterBlock( dataType( theBandNo ), theWidth, theHeight );
+    block->setNoDataValue( sourceNoDataValue( theBandNo ) );
   }
 
   if ( block->isEmpty() )
@@ -145,14 +141,10 @@ QgsRasterBlock * QgsRasterDataProvider::block( int theBandNo, QgsRectangle  cons
     QgsDebugMsgLevel( QString( "Reading smaller block tmpWidth = %1 theHeight = %2" ).arg( tmpWidth ).arg( tmpHeight ), 4 );
     QgsDebugMsgLevel( QString( "tmpExtent = %1" ).arg( tmpExtent.toString() ), 4 );
 
-    QgsRasterBlock *tmpBlock;
+    QgsRasterBlock *tmpBlock = new QgsRasterBlock( dataType( theBandNo ), tmpWidth, tmpHeight );
     if ( sourceHasNoDataValue( theBandNo ) && useSourceNoDataValue( theBandNo ) )
     {
-      tmpBlock = new QgsRasterBlock( dataType( theBandNo ), tmpWidth, tmpHeight, sourceNoDataValue( theBandNo ) );
-    }
-    else
-    {
-      tmpBlock = new QgsRasterBlock( dataType( theBandNo ), tmpWidth, tmpHeight );
+      tmpBlock->setNoDataValue( sourceNoDataValue( theBandNo ) );
     }
 
     readBlock( theBandNo, tmpExtent, tmpWidth, tmpHeight, tmpBlock->bits(), feedback );

diff --git a/src/core/raster/qgsrasternuller.cpp b/src/core/raster/qgsrasternuller.cpp
@@ -85,8 +85,7 @@ QgsRasterBlock * QgsRasterNuller::block( int bandNo, QgsRectangle  const & exten
     return inputBlock;
   }
 
-  QgsRasterBlock *outputBlock = nullptr;
-
+  QgsRasterBlock *outputBlock = new QgsRasterBlock( inputBlock->dataType(), width, height );
   if ( mHasOutputNoData.value( bandNo - 1 ) || inputBlock->hasNoDataValue() )
   {
     double noDataValue;
@@ -98,11 +97,7 @@ QgsRasterBlock * QgsRasterNuller::block( int bandNo, QgsRectangle  const & exten
     {
       noDataValue = inputBlock->noDataValue();
     }
-    outputBlock = new QgsRasterBlock( inputBlock->dataType(), width, height, noDataValue );
-  }
-  else
-  {
-    outputBlock = new QgsRasterBlock( inputBlock->dataType(), width, height );
+    outputBlock->setNoDataValue( noDataValue );
   }
 
   for ( int i = 0; i < height; i++ )

diff --git a/src/core/raster/qgsrasterprojector.cpp b/src/core/raster/qgsrasterprojector.cpp
@@ -781,14 +781,10 @@ QgsRasterBlock * QgsRasterProjector::block( int bandNo, QgsRectangle  const & ex
 
   qgssize pixelSize = QgsRasterBlock::typeSize( mInput->dataType( bandNo ) );
 
-  QgsRasterBlock *outputBlock;
+  QgsRasterBlock *outputBlock = new QgsRasterBlock( inputBlock->dataType(), width, height );
   if ( inputBlock->hasNoDataValue() )
   {
-    outputBlock = new QgsRasterBlock( inputBlock->dataType(), width, height, inputBlock->noDataValue() );
-  }
-  else
-  {
-    outputBlock = new QgsRasterBlock( inputBlock->dataType(), width, height );
+    outputBlock->setNoDataValue( inputBlock->noDataValue() );
   }
   if ( !outputBlock->isValid() )
   {

diff --git a/src/providers/gdal/qgsgdalprovider.cpp b/src/providers/gdal/qgsgdalprovider.cpp
@@ -389,15 +389,10 @@ QImage* QgsGdalProvider::draw( QgsRectangle  const & viewExtent, int pixelWidth,
 
 QgsRasterBlock* QgsGdalProvider::block( int theBandNo, const QgsRectangle &theExtent, int theWidth, int theHeight, QgsRasterBlockFeedback* feedback )
 {
-  //QgsRasterBlock *block = new QgsRasterBlock( dataType( theBandNo ), theWidth, theHeight, noDataValue( theBandNo ) );
-  QgsRasterBlock *block;
+  QgsRasterBlock *block = new QgsRasterBlock( dataType( theBandNo ), theWidth, theHeight );
   if ( sourceHasNoDataValue( theBandNo ) && useSourceNoDataValue( theBandNo ) )
   {
-    block = new QgsRasterBlock( dataType( theBandNo ), theWidth, theHeight, sourceNoDataValue( theBandNo ) );
-  }
-  else
-  {
-    block = new QgsRasterBlock( dataType( theBandNo ), theWidth, theHeight );
+    block->setNoDataValue( sourceNoDataValue( theBandNo ) );
   }
 
   if ( block->isEmpty() )