QGIS API Documentation  3.13.0-Master (b73bd58cfb)
qgsrasteriterator.cpp
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1 /***************************************************************************
2  qgsrasteriterator.cpp
3  ---------------------
4  begin : July 2012
5  copyright : (C) 2012 by Marco Hugentobler
6  email : marco dot hugentobler at sourcepole dot ch
7  ***************************************************************************
8  * *
9  * This program is free software; you can redistribute it and/or modify *
10  * it under the terms of the GNU General Public License as published by *
11  * the Free Software Foundation; either version 2 of the License, or *
12  * (at your option) any later version. *
13  * *
14  ***************************************************************************/
15 #include "qgsrasteriterator.h"
16 #include "qgsrasterinterface.h"
17 #include "qgsrasterprojector.h"
18 #include "qgsrasterviewport.h"
19 #include "qgsrasterdataprovider.h"
20 
22  : mInput( input )
23  , mMaximumTileWidth( DEFAULT_MAXIMUM_TILE_WIDTH )
24  , mMaximumTileHeight( DEFAULT_MAXIMUM_TILE_HEIGHT )
25 {
26  for ( QgsRasterInterface *ri = input; ri; ri = ri->input() )
27  {
28  QgsRasterDataProvider *rdp = dynamic_cast<QgsRasterDataProvider *>( ri );
29  if ( rdp )
30  {
31  mMaximumTileWidth = rdp->stepWidth();
32  mMaximumTileHeight = rdp->stepHeight();
33  break;
34  }
35  }
36 }
37 
38 void QgsRasterIterator::startRasterRead( int bandNumber, qgssize nCols, qgssize nRows, const QgsRectangle &extent, QgsRasterBlockFeedback *feedback )
39 {
40  if ( !mInput )
41  {
42  return;
43  }
44 
45  mExtent = extent;
46  mFeedback = feedback;
47 
48  //remove any previous part on that band
49  removePartInfo( bandNumber );
50 
51  //split raster into small portions if necessary
52  RasterPartInfo pInfo;
53  pInfo.nCols = nCols;
54  pInfo.nRows = nRows;
55  pInfo.currentCol = 0;
56  pInfo.currentRow = 0;
57  mRasterPartInfos.insert( bandNumber, pInfo );
58 }
59 
60 bool QgsRasterIterator::next( int bandNumber, int &columns, int &rows, int &topLeftColumn, int &topLeftRow, QgsRectangle &blockExtent )
61 {
62  return readNextRasterPartInternal( bandNumber, columns, rows, nullptr, topLeftColumn, topLeftRow, &blockExtent );
63 }
64 
66  int &nCols, int &nRows,
67  QgsRasterBlock **block,
68  int &topLeftCol, int &topLeftRow )
69 {
70  *block = nullptr;
71  std::unique_ptr< QgsRasterBlock > nextBlock;
72  bool result = readNextRasterPart( bandNumber, nCols, nRows, nextBlock, topLeftCol, topLeftRow );
73  if ( result )
74  *block = nextBlock.release();
75  return result;
76 }
77 
78 bool QgsRasterIterator::readNextRasterPart( int bandNumber, int &nCols, int &nRows, std::unique_ptr<QgsRasterBlock> &block, int &topLeftCol, int &topLeftRow, QgsRectangle *blockExtent )
79 {
80  return readNextRasterPartInternal( bandNumber, nCols, nRows, &block, topLeftCol, topLeftRow, blockExtent );
81 }
82 
83 bool QgsRasterIterator::readNextRasterPartInternal( int bandNumber, int &nCols, int &nRows, std::unique_ptr<QgsRasterBlock> *block, int &topLeftCol, int &topLeftRow, QgsRectangle *blockExtent )
84 {
85  QgsDebugMsgLevel( QStringLiteral( "Entered" ), 4 );
86  if ( block )
87  block->reset();
88  //get partinfo
89  QMap<int, RasterPartInfo>::iterator partIt = mRasterPartInfos.find( bandNumber );
90  if ( partIt == mRasterPartInfos.end() )
91  {
92  return false;
93  }
94 
95  RasterPartInfo &pInfo = partIt.value();
96 
97  // If we started with zero cols or zero rows, just return (avoids divide by zero below)
98  if ( 0 == pInfo.nCols || 0 == pInfo.nRows )
99  {
100  return false;
101  }
102 
103  //remove last data block
104 
105  //already at end
106  if ( pInfo.currentCol == pInfo.nCols && pInfo.currentRow == pInfo.nRows )
107  {
108  return false;
109  }
110 
111  //read data block
112  nCols = static_cast< int >( std::min( static_cast< qgssize >( mMaximumTileWidth ), pInfo.nCols - pInfo.currentCol ) );
113  nRows = static_cast< int >( std::min( static_cast< qgssize >( mMaximumTileHeight ), pInfo.nRows - pInfo.currentRow ) );
114  QgsDebugMsgLevel( QStringLiteral( "nCols = %1 nRows = %2" ).arg( nCols ).arg( nRows ), 4 );
115 
116  //get subrectangle
117  QgsRectangle viewPortExtent = mExtent;
118  double xmin = viewPortExtent.xMinimum() + pInfo.currentCol / static_cast< double >( pInfo.nCols ) * viewPortExtent.width();
119  double xmax = pInfo.currentCol + nCols == pInfo.nCols ? viewPortExtent.xMaximum() : // avoid extra FP math if not necessary
120  viewPortExtent.xMinimum() + ( pInfo.currentCol + nCols ) / static_cast< double >( pInfo.nCols ) * viewPortExtent.width();
121  double ymin = pInfo.currentRow + nRows == pInfo.nRows ? viewPortExtent.yMinimum() : // avoid extra FP math if not necessary
122  viewPortExtent.yMaximum() - ( pInfo.currentRow + nRows ) / static_cast< double >( pInfo.nRows ) * viewPortExtent.height();
123  double ymax = viewPortExtent.yMaximum() - pInfo.currentRow / static_cast< double >( pInfo.nRows ) * viewPortExtent.height();
124  QgsRectangle blockRect( xmin, ymin, xmax, ymax );
125 
126  if ( blockExtent )
127  *blockExtent = blockRect;
128 
129  if ( block )
130  block->reset( mInput->block( bandNumber, blockRect, nCols, nRows, mFeedback ) );
131  topLeftCol = pInfo.currentCol;
132  topLeftRow = pInfo.currentRow;
133 
134  pInfo.currentCol += nCols;
135  if ( pInfo.currentCol == pInfo.nCols && pInfo.currentRow + nRows == pInfo.nRows ) //end of raster
136  {
137  pInfo.currentRow = pInfo.nRows;
138  }
139  else if ( pInfo.currentCol == pInfo.nCols ) //start new row
140  {
141  pInfo.currentCol = 0;
142  pInfo.currentRow += nRows;
143  }
144 
145  return true;
146 }
147 
148 void QgsRasterIterator::stopRasterRead( int bandNumber )
149 {
150  removePartInfo( bandNumber );
151 }
152 
153 void QgsRasterIterator::removePartInfo( int bandNumber )
154 {
155  auto partIt = mRasterPartInfos.constFind( bandNumber );
156  if ( partIt != mRasterPartInfos.constEnd() )
157  {
158  mRasterPartInfos.remove( bandNumber );
159  }
160 }
A rectangle specified with double values.
Definition: qgsrectangle.h:41
QgsRasterIterator(QgsRasterInterface *input)
Constructor for QgsRasterIterator, iterating over the specified input raster source.
virtual QgsRasterInterface * input() const
Current input.
bool next(int bandNumber, int &columns, int &rows, int &topLeftColumn, int &topLeftRow, QgsRectangle &blockExtent)
Fetches details of the next part of the raster data.
Raster data container.
#define QgsDebugMsgLevel(str, level)
Definition: qgslogger.h:39
virtual QgsRasterBlock * block(int bandNo, const QgsRectangle &extent, int width, int height, QgsRasterBlockFeedback *feedback=nullptr)=0
Read block of data using given extent and size.
void startRasterRead(int bandNumber, qgssize nCols, qgssize nRows, const QgsRectangle &extent, QgsRasterBlockFeedback *feedback=nullptr)
Start reading of raster band.
double width() const
Returns the width of the rectangle.
Definition: qgsrectangle.h:202
bool readNextRasterPart(int bandNumber, int &nCols, int &nRows, QgsRasterBlock **block, int &topLeftCol, int &topLeftRow)
Fetches next part of raster data, caller takes ownership of the block and caller should delete the bl...
Base class for processing filters like renderers, reprojector, resampler etc.
unsigned long long qgssize
Qgssize is used instead of size_t, because size_t is stdlib type, unknown by SIP, and it would be har...
Definition: qgis.h:703
void stopRasterRead(int bandNumber)
Cancels the raster iteration and resets the iterator.
double yMinimum() const
Returns the y minimum value (bottom side of rectangle).
Definition: qgsrectangle.h:177
double xMaximum() const
Returns the x maximum value (right side of rectangle).
Definition: qgsrectangle.h:162
virtual int stepHeight() const
Step height for raster iterations.
double xMinimum() const
Returns the x minimum value (left side of rectangle).
Definition: qgsrectangle.h:167
virtual int stepWidth() const
Step width for raster iterations.
double yMaximum() const
Returns the y maximum value (top side of rectangle).
Definition: qgsrectangle.h:172
Feedback object tailored for raster block reading.
double height() const
Returns the height of the rectangle.
Definition: qgsrectangle.h:209
Base class for raster data providers.