QGIS API Documentation 3.40.0-Bratislava (b56115d8743)
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Classes | Public Member Functions | Static Public Member Functions | Static Public Attributes | List of all members
QgsRasterIterator Class Reference

Iterator for sequentially processing raster cells. More...

#include <qgsrasteriterator.h>

Public Member Functions

 QgsRasterIterator (QgsRasterInterface *input, int tileOverlapPixels=0)
 Constructor for QgsRasterIterator, iterating over the specified input raster source.
 
const QgsRasterInterfaceinput () const
 Returns the input raster interface which is being iterated over.
 
int maximumTileHeight () const
 Returns the minimum tile width returned during iteration.
 
int maximumTileWidth () const
 Returns the maximum tile width returned during iteration.
 
bool next (int bandNumber, int &columns, int &rows, int &topLeftColumn, int &topLeftRow, QgsRectangle &blockExtent)
 Fetches details of the next part of the raster data.
 
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 block.
 
bool readNextRasterPart (int bandNumber, int &nCols, int &nRows, std::unique_ptr< QgsRasterBlock > &block, int &topLeftCol, int &topLeftRow, QgsRectangle *blockExtent=nullptr, int *tileColumns=nullptr, int *tileRows=nullptr, int *tileTopLeftColumn=nullptr, int *tileTopLeftRow=nullptr)
 Fetches next part of raster data.
 
void setMaximumTileHeight (int h)
 Sets the minimum tile height returned during iteration.
 
void setMaximumTileWidth (int w)
 Sets the maximum tile width returned during iteration.
 
void startRasterRead (int bandNumber, qgssize nCols, qgssize nRows, const QgsRectangle &extent, QgsRasterBlockFeedback *feedback=nullptr)
 Start reading of raster band.
 
void stopRasterRead (int bandNumber)
 Cancels the raster iteration and resets the iterator.
 

Static Public Member Functions

static QgsRectangle subRegion (const QgsRectangle &rasterExtent, int rasterWidth, int rasterHeight, const QgsRectangle &subRegion, int &subRegionWidth, int &subRegionHeight, int &subRegionLeft, int &subRegionTop)
 Given an overall raster extent and width and height in pixels, calculates the sub region of the raster covering the specified subRegion.
 

Static Public Attributes

static const int DEFAULT_MAXIMUM_TILE_HEIGHT = 2000
 Default maximum tile height.
 
static const int DEFAULT_MAXIMUM_TILE_WIDTH = 2000
 Default maximum tile width.
 

Detailed Description

Iterator for sequentially processing raster cells.

Definition at line 34 of file qgsrasteriterator.h.

Constructor & Destructor Documentation

◆ QgsRasterIterator()

QgsRasterIterator::QgsRasterIterator ( QgsRasterInterface input,
int  tileOverlapPixels = 0 
)

Constructor for QgsRasterIterator, iterating over the specified input raster source.

Since QGIS 3.34 the tileOverlapPixels can be used to specify a margin in pixels for retrieving pixels overlapping into neighbor cells.

Definition at line 19 of file qgsrasteriterator.cpp.

Member Function Documentation

◆ input()

const QgsRasterInterface * QgsRasterIterator::input ( ) const
inline

Returns the input raster interface which is being iterated over.

Definition at line 143 of file qgsrasteriterator.h.

◆ maximumTileHeight()

int QgsRasterIterator::maximumTileHeight ( ) const
inline

Returns the minimum tile width returned during iteration.

See also
setMaximumTileHeight()
maximumTileWidth()

Definition at line 171 of file qgsrasteriterator.h.

◆ maximumTileWidth()

int QgsRasterIterator::maximumTileWidth ( ) const
inline

Returns the maximum tile width returned during iteration.

See also
setMaximumTileWidth()
maximumTileHeight()

Definition at line 157 of file qgsrasteriterator.h.

◆ next()

bool QgsRasterIterator::next ( int  bandNumber,
int &  columns,
int &  rows,
int &  topLeftColumn,
int &  topLeftRow,
QgsRectangle blockExtent 
)

Fetches details of the next part of the raster data.

This method does NOT actually fetch the raster data itself, rather it calculates and iterates over the details of the raster alone.

It's useful for iterating over several layers using a target "reference" layer. E.g. summing the pixels in n rasters whilst aligning the result to a reference layer which is not being summed.

Note that calling this method also advances the iterator, just like calling readNextRasterPart().

Parameters
bandNumberband to read
columnsnumber of columns on output device
rowsnumber of rows on output device
topLeftColumntop left column
topLeftRowtop left row
blockExtentexact extent of returned raster block
Returns
false if the last part was already returned
Since
QGIS 3.6

Definition at line 98 of file qgsrasteriterator.cpp.

◆ readNextRasterPart() [1/2]

bool QgsRasterIterator::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 block.

Parameters
bandNumberband to read
nColsnumber of columns on output device
nRowsnumber of rows on output device
blockaddress of block pointer
topLeftColtop left column
topLeftRowtop left row
Returns
false if the last part was already returned

Definition at line 107 of file qgsrasteriterator.cpp.

◆ readNextRasterPart() [2/2]

bool QgsRasterIterator::readNextRasterPart ( int  bandNumber,
int &  nCols,
int &  nRows,
std::unique_ptr< QgsRasterBlock > &  block,
int &  topLeftCol,
int &  topLeftRow,
QgsRectangle blockExtent = nullptr,
int *  tileColumns = nullptr,
int *  tileRows = nullptr,
int *  tileTopLeftColumn = nullptr,
int *  tileTopLeftRow = nullptr 
)

Fetches next part of raster data.

Parameters
bandNumberband to read
nColsnumber of columns on output device
nRowsnumber of rows on output device
blockaddress of block pointer
topLeftColtop left column
topLeftRowtop left row
blockExtentoptional storage for exact extent of returned raster block
tileColumnsoptional storage for number of columns in the iterated tile (excluding any tile overlap pixels)
tileRowsoptional storage for number of rows in the iterated tile (excluding any tile overlap pixels)
tileTopLeftColumnoptional storage for the top left column in the iterated tile (excluding any tile overlap pixels)
tileTopLeftRowoptional storage for the top left row in the iterated tile (excluding any tile overlap pixels)
Returns
false if the last part was already returned
Note
Not available in Python bindings
Since
QGIS 3.2

Definition at line 120 of file qgsrasteriterator.cpp.

◆ setMaximumTileHeight()

void QgsRasterIterator::setMaximumTileHeight ( int  h)
inline

Sets the minimum tile height returned during iteration.

See also
maximumTileHeight()
setMaximumTileWidth()

Definition at line 164 of file qgsrasteriterator.h.

◆ setMaximumTileWidth()

void QgsRasterIterator::setMaximumTileWidth ( int  w)
inline

Sets the maximum tile width returned during iteration.

See also
maximumTileWidth()
setMaximumTileHeight()

Definition at line 150 of file qgsrasteriterator.h.

◆ startRasterRead()

void QgsRasterIterator::startRasterRead ( int  bandNumber,
qgssize  nCols,
qgssize  nRows,
const QgsRectangle extent,
QgsRasterBlockFeedback feedback = nullptr 
)

Start reading of raster band.

Raster data can then be retrieved by calling readNextRasterPart until it returns false.

Parameters
bandNumbernumber of raster band to read
nColsnumber of columns
nRowsnumber of rows
extentarea to read
feedbackoptional raster feedback object for cancellation/preview. Added in QGIS 3.0.

Definition at line 76 of file qgsrasteriterator.cpp.

◆ stopRasterRead()

void QgsRasterIterator::stopRasterRead ( int  bandNumber)

Cancels the raster iteration and resets the iterator.

Definition at line 219 of file qgsrasteriterator.cpp.

◆ subRegion()

QgsRectangle QgsRasterIterator::subRegion ( const QgsRectangle rasterExtent,
int  rasterWidth,
int  rasterHeight,
const QgsRectangle subRegion,
int &  subRegionWidth,
int &  subRegionHeight,
int &  subRegionLeft,
int &  subRegionTop 
)
static

Given an overall raster extent and width and height in pixels, calculates the sub region of the raster covering the specified subRegion.

Parameters
rasterExtentoverall raster extent
rasterWidthoverall raster width
rasterHeightoverall raster height
subRegiondesired sub region extent
subRegionWidthwidth in pixels of sub region
subRegionHeightheight in pixels of sub region
subRegionLeftstarting column of left side of sub region
subRegionTopstarting row of top side of sub region
Returns
sub region geographic extent, snapped to exact pixel boundaries
Since
QGIS 3.26

Definition at line 37 of file qgsrasteriterator.cpp.

Member Data Documentation

◆ DEFAULT_MAXIMUM_TILE_HEIGHT

const int QgsRasterIterator::DEFAULT_MAXIMUM_TILE_HEIGHT = 2000
static

Default maximum tile height.

Definition at line 177 of file qgsrasteriterator.h.

◆ DEFAULT_MAXIMUM_TILE_WIDTH

const int QgsRasterIterator::DEFAULT_MAXIMUM_TILE_WIDTH = 2000
static

Default maximum tile width.

Definition at line 174 of file qgsrasteriterator.h.


The documentation for this class was generated from the following files: