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GDALRasterBand Class Reference

A single raster band (or channel). More...

#include <gdal_priv.h>

Inheritance diagram for GDALRasterBand:
GDALMajorObject GDALAllValidMaskBand GDALNoDataMaskBand GDALNoDataValuesMaskBand GDALPamRasterBand GDALProxyRasterBand VRTRasterBand GDALProxyPoolRasterBand VRTRawRasterBand VRTSourcedRasterBand VRTWarpedRasterBand GDALProxyPoolMaskBand GDALProxyPoolOverviewRasterBand VRTDerivedRasterBand

List of all members.

Public Member Functions

 GDALRasterBand ()
virtual ~GDALRasterBand ()
int GetXSize ()
 Fetch XSize of raster.
int GetYSize ()
 Fetch YSize of raster.
int GetBand ()
 Fetch the band number.
GDALDatasetGetDataset ()
 Fetch the owning dataset handle.
GDALDataType GetRasterDataType (void)
 Fetch the pixel data type for this band.
void GetBlockSize (int *, int *)
 Fetch the "natural" block size of this band.
GDALAccess GetAccess ()
 Find out if we have update permission for this band.
CPLErr RasterIO (GDALRWFlag, int, int, int, int, void *, int, int, GDALDataType, int, int)
 Read/write a region of image data for this band.
CPLErr ReadBlock (int, int, void *)
 Read a block of image data efficiently.
CPLErr WriteBlock (int, int, void *)
 Write a block of image data efficiently.
GDALRasterBlockGetLockedBlockRef (int nXBlockOff, int nYBlockOff, int bJustInitialize=FALSE)
 Fetch a pointer to an internally cached raster block.
CPLErr FlushBlock (int=-1, int=-1, int bWriteDirtyBlock=TRUE)
unsigned char * GetIndexColorTranslationTo (GDALRasterBand *poReferenceBand, unsigned char *pTranslationTable=NULL, int *pApproximateMatching=NULL)
 Compute translation table for color tables.
virtual CPLErr FlushCache ()
 Flush raster data cache.
virtual char ** GetCategoryNames ()
 Fetch the list of category names for this raster.
virtual double GetNoDataValue (int *pbSuccess=NULL)
 Fetch the no data value for this band.
virtual double GetMinimum (int *pbSuccess=NULL)
 Fetch the minimum value for this band.
virtual double GetMaximum (int *pbSuccess=NULL)
 Fetch the maximum value for this band.
virtual double GetOffset (int *pbSuccess=NULL)
 Fetch the raster value offset.
virtual double GetScale (int *pbSuccess=NULL)
 Fetch the raster value scale.
virtual const char * GetUnitType ()
 Return raster unit type.
virtual GDALColorInterp GetColorInterpretation ()
 How should this band be interpreted as color?
virtual GDALColorTableGetColorTable ()
 Fetch the color table associated with band.
virtual CPLErr Fill (double dfRealValue, double dfImaginaryValue=0)
 Fill this band with a constant value.
virtual CPLErr SetCategoryNames (char **)
 Set the category names for this band.
virtual CPLErr SetNoDataValue (double)
 Set the no data value for this band.
virtual CPLErr SetColorTable (GDALColorTable *)
 Set the raster color table.
virtual CPLErr SetColorInterpretation (GDALColorInterp)
 Set color interpretation of a band.
virtual CPLErr SetOffset (double)
 Set scaling offset.
virtual CPLErr SetScale (double)
 Set scaling ratio.
virtual CPLErr SetUnitType (const char *)
 Set unit type.
virtual CPLErr GetStatistics (int bApproxOK, int bForce, double *pdfMin, double *pdfMax, double *pdfMean, double *padfStdDev)
 Fetch image statistics.
virtual CPLErr ComputeStatistics (int bApproxOK, double *pdfMin, double *pdfMax, double *pdfMean, double *pdfStdDev, GDALProgressFunc, void *pProgressData)
 Compute image statistics.
virtual CPLErr SetStatistics (double dfMin, double dfMax, double dfMean, double dfStdDev)
 Set statistics on band.
virtual CPLErr ComputeRasterMinMax (int, double *)
virtual int HasArbitraryOverviews ()
 Check for arbitrary overviews.
virtual int GetOverviewCount ()
 Return the number of overview layers available.
virtual GDALRasterBandGetOverview (int)
 Fetch overview raster band object.
virtual GDALRasterBandGetRasterSampleOverview (int)
 Fetch best sampling overview.
virtual CPLErr BuildOverviews (const char *, int, int *, GDALProgressFunc, void *)
 Build raster overview(s).
virtual CPLErr AdviseRead (int nXOff, int nYOff, int nXSize, int nYSize, int nBufXSize, int nBufYSize, GDALDataType eDT, char **papszOptions)
 Advise driver of upcoming read requests.
virtual CPLErr GetHistogram (double dfMin, double dfMax, int nBuckets, int *panHistogram, int bIncludeOutOfRange, int bApproxOK, GDALProgressFunc, void *pProgressData)
 Compute raster histogram.
virtual CPLErr GetDefaultHistogram (double *pdfMin, double *pdfMax, int *pnBuckets, int **ppanHistogram, int bForce, GDALProgressFunc, void *pProgressData)
 Fetch default raster histogram.
virtual CPLErr SetDefaultHistogram (double dfMin, double dfMax, int nBuckets, int *panHistogram)
 Set default histogram.
virtual GDALRasterAttributeTableGetDefaultRAT ()
 Fetch default Raster Attribute Table.
virtual CPLErr SetDefaultRAT (const GDALRasterAttributeTable *)
 Set default Raster Attribute Table.
virtual GDALRasterBandGetMaskBand ()
 Return the mask band associated with the band.
virtual int GetMaskFlags ()
 Return the status flags of the mask band associated with the band.
virtual CPLErr CreateMaskBand (int nFlags)
 Adds a mask band to the current band.
virtual CPLVirtualMemGetVirtualMemAuto (GDALRWFlag eRWFlag, int *pnPixelSpace, GIntBig *pnLineSpace, char **papszOptions)
 Create a CPLVirtualMem object from a GDAL raster band object.
void ReportError (CPLErr eErrClass, int err_no, const char *fmt,...)
 Emits an error related to a raster band.

Protected Member Functions

void InvalidateMaskBand ()
virtual CPLErr IReadBlock (int, int, void *)=0
virtual CPLErr IWriteBlock (int, int, void *)
virtual CPLErr IRasterIO (GDALRWFlag, int, int, int, int, void *, int, int, GDALDataType, int, int)
CPLErr OverviewRasterIO (GDALRWFlag, int, int, int, int, void *, int, int, GDALDataType, int, int)
int InitBlockInfo ()
CPLErr AdoptBlock (int, int, GDALRasterBlock *)
GDALRasterBlockTryGetLockedBlockRef (int nXBlockOff, int nYBlockYOff)
 Try fetching block ref.

Protected Attributes

GDALDatasetpoDS
int nBand
int nRasterXSize
int nRasterYSize
GDALDataType eDataType
GDALAccess eAccess
int nBlockXSize
int nBlockYSize
int nBlocksPerRow
int nBlocksPerColumn
int bSubBlockingActive
int nSubBlocksPerRow
int nSubBlocksPerColumn
GDALRasterBlock ** papoBlocks
int nBlockReads
int bForceCachedIO
GDALRasterBandpoMask
bool bOwnMask
int nMaskFlags

Friends

class GDALRasterBlock
class GDALDataset
class GDALProxyRasterBand
class GDALDefaultOverviews

Detailed Description

A single raster band (or channel).


Constructor & Destructor Documentation

GDALRasterBand::GDALRasterBand (  ) 

Constructor. Applications should never create GDALRasterBands directly.

GDALRasterBand::~GDALRasterBand (  )  [virtual]

Destructor. Applications should never destroy GDALRasterBands directly, instead destroy the GDALDataset.


Member Function Documentation

CPLErr GDALRasterBand::AdviseRead ( int  nXOff,
int  nYOff,
int  nXSize,
int  nYSize,
int  nBufXSize,
int  nBufYSize,
GDALDataType  eBufType,
char **  papszOptions 
) [virtual]

Advise driver of upcoming read requests.

Some GDAL drivers operate more efficiently if they know in advance what set of upcoming read requests will be made. The AdviseRead() method allows an application to notify the driver of the region of interest, and at what resolution the region will be read.

Many drivers just ignore the AdviseRead() call, but it can dramatically accelerate access via some drivers.

Parameters:
nXOff The pixel offset to the top left corner of the region of the band to be accessed. This would be zero to start from the left side.
nYOff The line offset to the top left corner of the region of the band to be accessed. This would be zero to start from the top.
nXSize The width of the region of the band to be accessed in pixels.
nYSize The height of the region of the band to be accessed in lines.
nBufXSize the width of the buffer image into which the desired region is to be read, or from which it is to be written.
nBufYSize the height of the buffer image into which the desired region is to be read, or from which it is to be written.
eBufType the type of the pixel values in the pData data buffer. The pixel values will automatically be translated to/from the GDALRasterBand data type as needed.
papszOptions a list of name=value strings with special control options. Normally this is NULL.
Returns:
CE_Failure if the request is invalid and CE_None if it works or is ignored.

Reimplemented in GDALProxyRasterBand.

CPLErr GDALRasterBand::BuildOverviews ( const char *  pszResampling,
int  nOverviews,
int *  panOverviewList,
GDALProgressFunc  pfnProgress,
void *  pProgressData 
) [virtual]

Build raster overview(s).

If the operation is unsupported for the indicated dataset, then CE_Failure is returned, and CPLGetLastErrorNo() will return CPLE_NotSupported.

WARNING: It is not possible to build overviews for a single band in TIFF format, and thus this method does not work for TIFF format, or any formats that use the default overview building in TIFF format. Instead it is necessary to build overviews on the dataset as a whole using GDALDataset::BuildOverviews(). That makes this method pretty useless from a practical point of view.

Parameters:
pszResampling one of "NEAREST", "GAUSS", "CUBIC", "AVERAGE", "MODE", "AVERAGE_MAGPHASE" or "NONE" controlling the downsampling method applied.
nOverviews number of overviews to build.
panOverviewList the list of overview decimation factors to build.
pfnProgress a function to call to report progress, or NULL.
pProgressData application data to pass to the progress function.
Returns:
CE_None on success or CE_Failure if the operation doesn't work.

Reimplemented in GDALProxyRasterBand.

CPLErr GDALRasterBand::ComputeStatistics ( int  bApproxOK,
double *  pdfMin,
double *  pdfMax,
double *  pdfMean,
double *  pdfStdDev,
GDALProgressFunc  pfnProgress,
void *  pProgressData 
) [virtual]

Compute image statistics.

Returns the minimum, maximum, mean and standard deviation of all pixel values in this band. If approximate statistics are sufficient, the bApproxOK flag can be set to true in which case overviews, or a subset of image tiles may be used in computing the statistics.

Once computed, the statistics will generally be "set" back on the raster band using SetStatistics().

This method is the same as the C function GDALComputeRasterStatistics().

Parameters:
bApproxOK If TRUE statistics may be computed based on overviews or a subset of all tiles.
pdfMin Location into which to load image minimum (may be NULL).
pdfMax Location into which to load image maximum (may be NULL).-
pdfMean Location into which to load image mean (may be NULL).
pdfStdDev Location into which to load image standard deviation (may be NULL).
pfnProgress a function to call to report progress, or NULL.
pProgressData application data to pass to the progress function.
Returns:
CE_None on success, or CE_Failure if an error occurs or processing is terminated by the user.

Reimplemented in GDALProxyRasterBand, and VRTSourcedRasterBand.

CPLErr GDALRasterBand::CreateMaskBand ( int  nFlags  )  [virtual]

Adds a mask band to the current band.

The default implementation of the CreateMaskBand() method is implemented based on similar rules to the .ovr handling implemented using the GDALDefaultOverviews object. A TIFF file with the extension .msk will be created with the same basename as the original file, and it will have as many bands as the original image (or just one for GMF_PER_DATASET). The mask images will be deflate compressed tiled images with the same block size as the original image if possible.

Note that if you got a mask band with a previous call to GetMaskBand(), it might be invalidated by CreateMaskBand(). So you have to call GetMaskBand() again.

This method is the same as the C function GDALCreateMaskBand().

Since:
GDAL 1.5.0
Returns:
CE_None on success or CE_Failure on an error.
See also:
http://trac.osgeo.org/gdal/wiki/rfc15_nodatabitmask

Reimplemented in GDALProxyRasterBand, and VRTRasterBand.

CPLErr GDALRasterBand::Fill ( double  dfRealValue,
double  dfImaginaryValue = 0 
) [virtual]

Fill this band with a constant value.

GDAL makes no guarantees about what values pixels in newly created files are set to, so this method can be used to clear a band to a specified "default" value. The fill value is passed in as a double but this will be converted to the underlying type before writing to the file. An optional second argument allows the imaginary component of a complex constant value to be specified.

This method is the same as the C function GDALFillRaster().

Parameters:
dfRealValue Real component of fill value
dfImaginaryValue Imaginary component of fill value, defaults to zero
Returns:
CE_Failure if the write fails, otherwise CE_None

Reimplemented in GDALProxyRasterBand.

CPLErr GDALRasterBand::FlushCache ( void   )  [virtual]

Flush raster data cache.

This call will recover memory used to cache data blocks for this raster band, and ensure that new requests are referred to the underlying driver.

This method is the same as the C function GDALFlushRasterCache().

Returns:
CE_None on success.

Reimplemented in GDALProxyRasterBand.

GDALAccess GDALRasterBand::GetAccess (  ) 

Find out if we have update permission for this band.

This method is the same as the C function GDALGetRasterAccess().

Returns:
Either GA_Update or GA_ReadOnly.
int GDALRasterBand::GetBand (  ) 

Fetch the band number.

This method returns the band that this GDALRasterBand objects represents within it's dataset. This method may return a value of 0 to indicate GDALRasterBand objects without an apparently relationship to a dataset, such as GDALRasterBands serving as overviews.

This method is the same as the C function GDALGetBandNumber().

Returns:
band number (1+) or 0 if the band number isn't known.
void GDALRasterBand::GetBlockSize ( int *  pnXSize,
int *  pnYSize 
)

Fetch the "natural" block size of this band.

GDAL contains a concept of the natural block size of rasters so that applications can organized data access efficiently for some file formats. The natural block size is the block size that is most efficient for accessing the format. For many formats this is simple a whole scanline in which case *pnXSize is set to GetXSize(), and *pnYSize is set to 1.

However, for tiled images this will typically be the tile size.

Note that the X and Y block sizes don't have to divide the image size evenly, meaning that right and bottom edge blocks may be incomplete. See ReadBlock() for an example of code dealing with these issues.

This method is the same as the C function GDALGetBlockSize().

Parameters:
pnXSize integer to put the X block size into or NULL.
pnYSize integer to put the Y block size into or NULL.
char ** GDALRasterBand::GetCategoryNames (  )  [virtual]

Fetch the list of category names for this raster.

The return list is a "StringList" in the sense of the CPL functions. That is a NULL terminated array of strings. Raster values without associated names will have an empty string in the returned list. The first entry in the list is for raster values of zero, and so on.

The returned stringlist should not be altered or freed by the application. It may change on the next GDAL call, so please copy it if it is needed for any period of time.

This method is the same as the C function GDALGetRasterCategoryNames().

Returns:
list of names, or NULL if none.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, GDALProxyPoolRasterBand, and VRTRasterBand.

GDALColorInterp GDALRasterBand::GetColorInterpretation (  )  [virtual]

How should this band be interpreted as color?

GCI_Undefined is returned when the format doesn't know anything about the color interpretation.

This method is the same as the C function GDALGetRasterColorInterpretation().

Returns:
color interpretation value for band.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

GDALColorTable * GDALRasterBand::GetColorTable (  )  [virtual]

Fetch the color table associated with band.

If there is no associated color table, the return result is NULL. The returned color table remains owned by the GDALRasterBand, and can't be depended on for long, nor should it ever be modified by the caller.

This method is the same as the C function GDALGetRasterColorTable().

Returns:
internal color table, or NULL.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, GDALProxyPoolRasterBand, and VRTRasterBand.

GDALDataset * GDALRasterBand::GetDataset (  ) 

Fetch the owning dataset handle.

Note that some GDALRasterBands are not considered to be a part of a dataset, such as overviews or other "freestanding" bands.

This method is the same as the C function GDALGetBandDataset().

Returns:
the pointer to the GDALDataset to which this band belongs, or NULL if this cannot be determined.
CPLErr GDALRasterBand::GetDefaultHistogram ( double *  pdfMin,
double *  pdfMax,
int *  pnBuckets,
int **  ppanHistogram,
int  bForce,
GDALProgressFunc  pfnProgress,
void *  pProgressData 
) [virtual]

Fetch default raster histogram.

The default method in GDALRasterBand will compute a default histogram. This method is overriden by derived classes (such as GDALPamRasterBand, VRTDataset, HFADataset...) that may be able to fetch efficiently an already stored histogram.

This method is the same as the C function GDALGetDefaultHistogram().

Parameters:
pdfMin pointer to double value that will contain the lower bound of the histogram.
pdfMax pointer to double value that will contain the upper bound of the histogram.
pnBuckets pointer to int value that will contain the number of buckets in *ppanHistogram.
ppanHistogram pointer to array into which the histogram totals are placed. To be freed with VSIFree
bForce TRUE to force the computation. If FALSE and no default histogram is available, the method will return CE_Warning
pfnProgress function to report progress to completion.
pProgressData application data to pass to pfnProgress.
Returns:
CE_None on success, CE_Failure if something goes wrong, or CE_Warning if no default histogram is available.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

GDALRasterAttributeTable * GDALRasterBand::GetDefaultRAT (  )  [virtual]

Fetch default Raster Attribute Table.

A RAT will be returned if there is a default one associated with the band, otherwise NULL is returned. The returned RAT is owned by the band and should not be deleted by the application.

This method is the same as the C function GDALGetDefaultRAT().

Returns:
NULL, or a pointer to an internal RAT owned by the band.

Reimplemented in GDALPamRasterBand, and GDALProxyRasterBand.

CPLErr GDALRasterBand::GetHistogram ( double  dfMin,
double  dfMax,
int  nBuckets,
int *  panHistogram,
int  bIncludeOutOfRange,
int  bApproxOK,
GDALProgressFunc  pfnProgress,
void *  pProgressData 
) [virtual]

Compute raster histogram.

Note that the bucket size is (dfMax-dfMin) / nBuckets.

For example to compute a simple 256 entry histogram of eight bit data, the following would be suitable. The unusual bounds are to ensure that bucket boundaries don't fall right on integer values causing possible errors due to rounding after scaling.

    int anHistogram[256];
    poBand->GetHistogram( -0.5, 255.5, 256, anHistogram, FALSE, FALSE, 
                          GDALDummyProgress, NULL );

Note that setting bApproxOK will generally result in a subsampling of the file, and will utilize overviews if available. It should generally produce a representative histogram for the data that is suitable for use in generating histogram based luts for instance. Generally bApproxOK is much faster than an exactly computed histogram.

This method is the same as the C function GDALGetRasterHistogram().

Parameters:
dfMin the lower bound of the histogram.
dfMax the upper bound of the histogram.
nBuckets the number of buckets in panHistogram.
panHistogram array into which the histogram totals are placed.
bIncludeOutOfRange if TRUE values below the histogram range will mapped into panHistogram[0], and values above will be mapped into panHistogram[nBuckets-1] otherwise out of range values are discarded.
bApproxOK TRUE if an approximate, or incomplete histogram OK.
pfnProgress function to report progress to completion.
pProgressData application data to pass to pfnProgress.
Returns:
CE_None on success, or CE_Failure if something goes wrong.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, VRTRasterBand, and VRTSourcedRasterBand.

unsigned char * GDALRasterBand::GetIndexColorTranslationTo ( GDALRasterBand poReferenceBand,
unsigned char *  pTranslationTable = NULL,
int *  pApproximateMatching = NULL 
)

Compute translation table for color tables.

When the raster band has a palette index, it may be usefull to compute the "translation" of this palette to the palette of another band. The translation tries to do exact matching first, and then approximate matching if no exact matching is possible. This method returns a table such that table[i] = j where i is an index of the 'this' rasterband and j the corresponding index for the reference rasterband.

This method is thought as internal to GDAL and is used for drivers like RPFTOC.

The implementation only supports 1-byte palette rasterbands.

Parameters:
poReferenceBand the raster band
pTranslationTable an already allocated translation table (at least 256 bytes), or NULL to let the method allocate it
pApproximateMatching a pointer to a flag that is set if the matching is approximate. May be NULL.
Returns:
a translation table if the two bands are palette index and that they do not match or NULL in other cases. The table must be freed with CPLFree if NULL was passed for pTranslationTable.
GDALRasterBlock * GDALRasterBand::GetLockedBlockRef ( int  nXBlockOff,
int  nYBlockOff,
int  bJustInitialize = FALSE 
)

Fetch a pointer to an internally cached raster block.

This method will returned the requested block (locked) if it is already in the block cache for the layer. If not, the block will be read from the driver, and placed in the layer block cached, then returned. If an error occurs reading the block from the driver, a NULL value will be returned.

If a non-NULL value is returned, then a lock for the block will have been acquired on behalf of the caller. It is absolutely imperative that the caller release this lock (with GDALRasterBlock::DropLock()) or else severe problems may result.

Note that calling GetLockedBlockRef() on a previously uncached band will enable caching.

Parameters:
nXBlockOff the horizontal block offset, with zero indicating the left most block, 1 the next block and so forth.
nYBlockOff the vertical block offset, with zero indicating the top most block, 1 the next block and so forth.
bJustInitialize If TRUE the block will be allocated and initialized, but not actually read from the source. This is useful when it will just be completely set and written back.
Returns:
pointer to the block object, or NULL on failure.
GDALRasterBand * GDALRasterBand::GetMaskBand (  )  [virtual]

Return the mask band associated with the band.

The GDALRasterBand class includes a default implementation of GetMaskBand() that returns one of four default implementations :

  • If a corresponding .msk file exists it will be used for the mask band.
  • If the dataset has a NODATA_VALUES metadata item, an instance of the new GDALNoDataValuesMaskBand class will be returned. GetMaskFlags() will return GMF_NODATA | GMF_PER_DATASET.
    Since:
    GDAL 1.6.0
  • If the band has a nodata value set, an instance of the new GDALNodataMaskRasterBand class will be returned. GetMaskFlags() will return GMF_NODATA.
  • If there is no nodata value, but the dataset has an alpha band that seems to apply to this band (specific rules yet to be determined) and that is of type GDT_Byte then that alpha band will be returned, and the flags GMF_PER_DATASET and GMF_ALPHA will be returned in the flags.
  • If neither of the above apply, an instance of the new GDALAllValidRasterBand class will be returned that has 255 values for all pixels. The null flags will return GMF_ALL_VALID.

Note that the GetMaskBand() should always return a GDALRasterBand mask, even if it is only an all 255 mask with the flags indicating GMF_ALL_VALID.

This method is the same as the C function GDALGetMaskBand().

Returns:
a valid mask band.
Since:
GDAL 1.5.0
See also:
http://trac.osgeo.org/gdal/wiki/rfc15_nodatabitmask

Reimplemented in GDALAllValidMaskBand, GDALProxyRasterBand, GDALProxyPoolRasterBand, and VRTRasterBand.

int GDALRasterBand::GetMaskFlags (  )  [virtual]

Return the status flags of the mask band associated with the band.

The GetMaskFlags() method returns an bitwise OR-ed set of status flags with the following available definitions that may be extended in the future:

  • GMF_ALL_VALID(0x01): There are no invalid pixels, all mask values will be 255. When used this will normally be the only flag set.
  • GMF_PER_DATASET(0x02): The mask band is shared between all bands on the dataset.
  • GMF_ALPHA(0x04): The mask band is actually an alpha band and may have values other than 0 and 255.
  • GMF_NODATA(0x08): Indicates the mask is actually being generated from nodata values. (mutually exclusive of GMF_ALPHA)

The GDALRasterBand class includes a default implementation of GetMaskBand() that returns one of four default implementations :

  • If a corresponding .msk file exists it will be used for the mask band.
  • If the dataset has a NODATA_VALUES metadata item, an instance of the new GDALNoDataValuesMaskBand class will be returned. GetMaskFlags() will return GMF_NODATA | GMF_PER_DATASET.
    Since:
    GDAL 1.6.0
  • If the band has a nodata value set, an instance of the new GDALNodataMaskRasterBand class will be returned. GetMaskFlags() will return GMF_NODATA.
  • If there is no nodata value, but the dataset has an alpha band that seems to apply to this band (specific rules yet to be determined) and that is of type GDT_Byte then that alpha band will be returned, and the flags GMF_PER_DATASET and GMF_ALPHA will be returned in the flags.
  • If neither of the above apply, an instance of the new GDALAllValidRasterBand class will be returned that has 255 values for all pixels. The null flags will return GMF_ALL_VALID.

This method is the same as the C function GDALGetMaskFlags().

Since:
GDAL 1.5.0
Returns:
a valid mask band.
See also:
http://trac.osgeo.org/gdal/wiki/rfc15_nodatabitmask

Reimplemented in GDALAllValidMaskBand, GDALProxyRasterBand, and VRTRasterBand.

double GDALRasterBand::GetMaximum ( int *  pbSuccess = NULL  )  [virtual]

Fetch the maximum value for this band.

For file formats that don't know this intrinsically, the maximum supported value for the data type will generally be returned.

This method is the same as the C function GDALGetRasterMaximum().

Parameters:
pbSuccess pointer to a boolean to use to indicate if the returned value is a tight maximum or not. May be NULL (default).
Returns:
the maximum raster value (excluding no data pixels)

Reimplemented in GDALProxyRasterBand, and VRTSourcedRasterBand.

double GDALRasterBand::GetMinimum ( int *  pbSuccess = NULL  )  [virtual]

Fetch the minimum value for this band.

For file formats that don't know this intrinsically, the minimum supported value for the data type will generally be returned.

This method is the same as the C function GDALGetRasterMinimum().

Parameters:
pbSuccess pointer to a boolean to use to indicate if the returned value is a tight minimum or not. May be NULL (default).
Returns:
the minimum raster value (excluding no data pixels)

Reimplemented in GDALProxyRasterBand, and VRTSourcedRasterBand.

double GDALRasterBand::GetNoDataValue ( int *  pbSuccess = NULL  )  [virtual]

Fetch the no data value for this band.

If there is no out of data value, an out of range value will generally be returned. The no data value for a band is generally a special marker value used to mark pixels that are not valid data. Such pixels should generally not be displayed, nor contribute to analysis operations.

This method is the same as the C function GDALGetRasterNoDataValue().

Parameters:
pbSuccess pointer to a boolean to use to indicate if a value is actually associated with this layer. May be NULL (default).
Returns:
the nodata value for this band.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

double GDALRasterBand::GetOffset ( int *  pbSuccess = NULL  )  [virtual]

Fetch the raster value offset.

This value (in combination with the GetScale() value) is used to transform raw pixel values into the units returned by GetUnits(). For example this might be used to store elevations in GUInt16 bands with a precision of 0.1, and starting from -100.

Units value = (raw value * scale) + offset

For file formats that don't know this intrinsically a value of zero is returned.

This method is the same as the C function GDALGetRasterOffset().

Parameters:
pbSuccess pointer to a boolean to use to indicate if the returned value is meaningful or not. May be NULL (default).
Returns:
the raster offset.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

GDALRasterBand * GDALRasterBand::GetOverview ( int  i  )  [virtual]

Fetch overview raster band object.

This method is the same as the C function GDALGetOverview().

Parameters:
i overview index between 0 and GetOverviewCount()-1.
Returns:
overview GDALRasterBand.

Reimplemented in GDALProxyRasterBand, GDALProxyPoolRasterBand, VRTRasterBand, and VRTWarpedRasterBand.

int GDALRasterBand::GetOverviewCount (  )  [virtual]

Return the number of overview layers available.

This method is the same as the C function GDALGetOverviewCount().

Returns:
overview count, zero if none.

Reimplemented in GDALProxyRasterBand, VRTRasterBand, and VRTWarpedRasterBand.

GDALDataType GDALRasterBand::GetRasterDataType ( void   ) 

Fetch the pixel data type for this band.

This method is the same as the C function GDALGetRasterDataType().

Returns:
the data type of pixels for this band.
GDALRasterBand * GDALRasterBand::GetRasterSampleOverview ( int  nDesiredSamples  )  [virtual]

Fetch best sampling overview.

Returns the most reduced overview of the given band that still satisfies the desired number of samples. This function can be used with zero as the number of desired samples to fetch the most reduced overview. The same band as was passed in will be returned if it has not overviews, or if none of the overviews have enough samples.

This method is the same as the C function GDALGetRasterSampleOverview().

Parameters:
nDesiredSamples the returned band will have at least this many pixels.
Returns:
optimal overview or the band itself.

Reimplemented in GDALProxyRasterBand, and GDALProxyPoolRasterBand.

double GDALRasterBand::GetScale ( int *  pbSuccess = NULL  )  [virtual]

Fetch the raster value scale.

This value (in combination with the GetOffset() value) is used to transform raw pixel values into the units returned by GetUnits(). For example this might be used to store elevations in GUInt16 bands with a precision of 0.1, and starting from -100.

Units value = (raw value * scale) + offset

For file formats that don't know this intrinsically a value of one is returned.

This method is the same as the C function GDALGetRasterScale().

Parameters:
pbSuccess pointer to a boolean to use to indicate if the returned value is meaningful or not. May be NULL (default).
Returns:
the raster scale.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

CPLErr GDALRasterBand::GetStatistics ( int  bApproxOK,
int  bForce,
double *  pdfMin,
double *  pdfMax,
double *  pdfMean,
double *  pdfStdDev 
) [virtual]

Fetch image statistics.

Returns the minimum, maximum, mean and standard deviation of all pixel values in this band. If approximate statistics are sufficient, the bApproxOK flag can be set to true in which case overviews, or a subset of image tiles may be used in computing the statistics.

If bForce is FALSE results will only be returned if it can be done quickly (ie. without scanning the data). If bForce is FALSE and results cannot be returned efficiently, the method will return CE_Warning but no warning will have been issued. This is a non-standard use of the CE_Warning return value to indicate "nothing done".

Note that file formats using PAM (Persistent Auxilary Metadata) services will generally cache statistics in the .pam file allowing fast fetch after the first request.

This method is the same as the C function GDALGetRasterStatistics().

Parameters:
bApproxOK If TRUE statistics may be computed based on overviews or a subset of all tiles.
bForce If FALSE statistics will only be returned if it can be done without rescanning the image.
pdfMin Location into which to load image minimum (may be NULL).
pdfMax Location into which to load image maximum (may be NULL).-
pdfMean Location into which to load image mean (may be NULL).
pdfStdDev Location into which to load image standard deviation (may be NULL).
Returns:
CE_None on success, CE_Warning if no values returned, CE_Failure if an error occurs.

Reimplemented in GDALProxyRasterBand.

const char * GDALRasterBand::GetUnitType (  )  [virtual]

Return raster unit type.

Return a name for the units of this raster's values. For instance, it might be "m" for an elevation model in meters, or "ft" for feet. If no units are available, a value of "" will be returned. The returned string should not be modified, nor freed by the calling application.

This method is the same as the C function GDALGetRasterUnitType().

Returns:
unit name string.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, GDALProxyPoolRasterBand, and VRTRasterBand.

CPLVirtualMem * GDALRasterBand::GetVirtualMemAuto ( GDALRWFlag  eRWFlag,
int *  pnPixelSpace,
GIntBig *  pnLineSpace,
char **  papszOptions 
) [virtual]

Create a CPLVirtualMem object from a GDAL raster band object.

Only supported on Linux for now.

This method allows creating a virtual memory object for a GDALRasterBand, that exposes the whole image data as a virtual array.

The default implementation relies on GDALRasterBandGetVirtualMem(), but specialized implementation, such as for raw files, may also directly use mechanisms of the operating system to create a view of the underlying file into virtual memory ( CPLVirtualMemFileMapNew() )

At the time of writing, the GeoTIFF driver and "raw" drivers (EHdr, ...) offer a specialized implementation with direct file mapping, provided that some requirements are met :

  • for all drivers, the dataset must be backed by a "real" file in the file system, and the byte ordering of multi-byte datatypes (Int16, etc.) must match the native ordering of the CPU.
  • in addition, for the GeoTIFF driver, the GeoTIFF file must be uncompressed, scanline oriented (i.e. not tiled). Strips must be organized in the file in sequential order, and be equally spaced (which is generally the case). Only power-of-two bit depths are supported (8 for GDT_Bye, 16 for GDT_Int16/GDT_UInt16, 32 for GDT_Float32 and 64 for GDT_Float64)

The pointer returned remains valid until CPLVirtualMemFree() is called. CPLVirtualMemFree() must be called before the raster band object is destroyed.

If p is such a pointer and base_type the type matching GDALGetRasterDataType(), the element of image coordinates (x, y) can be accessed with *(base_type*) ((GByte*)p + x * *pnPixelSpace + y * *pnLineSpace)

This method is the same as the C GDALGetVirtualMemAuto() function.

Parameters:
eRWFlag Either GF_Read to read the band, or GF_Write to read/write the band.
pnPixelSpace Output parameter giving the byte offset from the start of one pixel value in the buffer to the start of the next pixel value within a scanline.
pnLineSpace Output parameter giving the byte offset from the start of one scanline in the buffer to the start of the next.
papszOptions NULL terminated list of options. If a specialized implementation exists, defining USE_DEFAULT_IMPLEMENTATION=YES will cause the default implementation to be used. When requiring or falling back to the default implementation, the following options are available : CACHE_SIZE (in bytes, defaults to 40 MB), PAGE_SIZE_HINT (in bytes), SINGLE_THREAD ("FALSE" / "TRUE", defaults to FALSE)
Returns:
a virtual memory object that must be unreferenced by CPLVirtualMemFree(), or NULL in case of failure.
Since:
GDAL 1.11

Reimplemented in GDALProxyRasterBand.

int GDALRasterBand::GetXSize (  ) 

Fetch XSize of raster.

This method is the same as the C function GDALGetRasterBandXSize().

Returns:
the width in pixels of this band.
int GDALRasterBand::GetYSize (  ) 

Fetch YSize of raster.

This method is the same as the C function GDALGetRasterBandYSize().

Returns:
the height in pixels of this band.
int GDALRasterBand::HasArbitraryOverviews (  )  [virtual]

Check for arbitrary overviews.

This returns TRUE if the underlying datastore can compute arbitrary overviews efficiently, such as is the case with OGDI over a network. Datastores with arbitrary overviews don't generally have any fixed overviews, but the RasterIO() method can be used in downsampling mode to get overview data efficiently.

This method is the same as the C function GDALHasArbitraryOverviews(),

Returns:
TRUE if arbitrary overviews available (efficiently), otherwise FALSE.

Reimplemented in GDALProxyRasterBand.

CPLErr GDALRasterBand::RasterIO ( GDALRWFlag  eRWFlag,
int  nXOff,
int  nYOff,
int  nXSize,
int  nYSize,
void *  pData,
int  nBufXSize,
int  nBufYSize,
GDALDataType  eBufType,
int  nPixelSpace,
int  nLineSpace 
)

Read/write a region of image data for this band.

This method allows reading a region of a GDALRasterBand into a buffer, or writing data from a buffer into a region of a GDALRasterBand. It automatically takes care of data type translation if the data type (eBufType) of the buffer is different than that of the GDALRasterBand. The method also takes care of image decimation / replication if the buffer size (nBufXSize x nBufYSize) is different than the size of the region being accessed (nXSize x nYSize).

The nPixelSpace and nLineSpace parameters allow reading into or writing from unusually organized buffers. This is primarily used for buffers containing more than one bands raster data in interleaved format.

Some formats may efficiently implement decimation into a buffer by reading from lower resolution overview images.

For highest performance full resolution data access, read and write on "block boundaries" as returned by GetBlockSize(), or use the ReadBlock() and WriteBlock() methods.

This method is the same as the C GDALRasterIO() function.

Parameters:
eRWFlag Either GF_Read to read a region of data, or GF_Write to write a region of data.
nXOff The pixel offset to the top left corner of the region of the band to be accessed. This would be zero to start from the left side.
nYOff The line offset to the top left corner of the region of the band to be accessed. This would be zero to start from the top.
nXSize The width of the region of the band to be accessed in pixels.
nYSize The height of the region of the band to be accessed in lines.
pData The buffer into which the data should be read, or from which it should be written. This buffer must contain at least nBufXSize * nBufYSize words of type eBufType. It is organized in left to right, top to bottom pixel order. Spacing is controlled by the nPixelSpace, and nLineSpace parameters.
nBufXSize the width of the buffer image into which the desired region is to be read, or from which it is to be written.
nBufYSize the height of the buffer image into which the desired region is to be read, or from which it is to be written.
eBufType the type of the pixel values in the pData data buffer. The pixel values will automatically be translated to/from the GDALRasterBand data type as needed.
nPixelSpace The byte offset from the start of one pixel value in pData to the start of the next pixel value within a scanline. If defaulted (0) the size of the datatype eBufType is used.
nLineSpace The byte offset from the start of one scanline in pData to the start of the next. If defaulted (0) the size of the datatype eBufType * nBufXSize is used.
Returns:
CE_Failure if the access fails, otherwise CE_None.
CPLErr GDALRasterBand::ReadBlock ( int  nXBlockOff,
int  nYBlockOff,
void *  pImage 
)

Read a block of image data efficiently.

This method accesses a "natural" block from the raster band without resampling, or data type conversion. For a more generalized, but potentially less efficient access use RasterIO().

This method is the same as the C GDALReadBlock() function.

See the GetLockedBlockRef() method for a way of accessing internally cached block oriented data without an extra copy into an application buffer.

Parameters:
nXBlockOff the horizontal block offset, with zero indicating the left most block, 1 the next block and so forth.
nYBlockOff the vertical block offset, with zero indicating the left most block, 1 the next block and so forth.
pImage the buffer into which the data will be read. The buffer must be large enough to hold GetBlockXSize()*GetBlockYSize() words of type GetRasterDataType().
Returns:
CE_None on success or CE_Failure on an error.

The following code would efficiently compute a histogram of eight bit raster data. Note that the final block may be partial ... data beyond the edge of the underlying raster band in these edge blocks is of an undermined value.

 CPLErr GetHistogram( GDALRasterBand *poBand, int *panHistogram )
 {
     int        nXBlocks, nYBlocks, nXBlockSize, nYBlockSize;
     int        iXBlock, iYBlock;
     GByte      *pabyData;
     memset( panHistogram, 0, sizeof(int) * 256 );
     CPLAssert( poBand->GetRasterDataType() == GDT_Byte );
     poBand->GetBlockSize( &nXBlockSize, &nYBlockSize );
     nXBlocks = (poBand->GetXSize() + nXBlockSize - 1) / nXBlockSize;
     nYBlocks = (poBand->GetYSize() + nYBlockSize - 1) / nYBlockSize;
     pabyData = (GByte *) CPLMalloc(nXBlockSize * nYBlockSize);
     for( iYBlock = 0; iYBlock < nYBlocks; iYBlock++ )
     {
         for( iXBlock = 0; iXBlock < nXBlocks; iXBlock++ )
         {
             int        nXValid, nYValid;
             poBand->ReadBlock( iXBlock, iYBlock, pabyData );
             // Compute the portion of the block that is valid
             // for partial edge blocks.
             if( (iXBlock+1) * nXBlockSize > poBand->GetXSize() )
                 nXValid = poBand->GetXSize() - iXBlock * nXBlockSize;
             else
                 nXValid = nXBlockSize;
             if( (iYBlock+1) * nYBlockSize > poBand->GetYSize() )
                 nYValid = poBand->GetYSize() - iYBlock * nYBlockSize;
             else
                 nYValid = nYBlockSize;
             // Collect the histogram counts.
             for( int iY = 0; iY < nYValid; iY++ )
             {
                 for( int iX = 0; iX < nXValid; iX++ )
                 {
                     panHistogram[pabyData[iX + iY * nXBlockSize]] += 1;
                 }
             }
         }
     }
 }
 
void GDALRasterBand::ReportError ( CPLErr  eErrClass,
int  err_no,
const char *  fmt,
  ... 
)

Emits an error related to a raster band.

This function is a wrapper for regular CPLError(). The only difference with CPLError() is that it prepends the error message with the dataset name and the band number.

Parameters:
eErrClass one of CE_Warning, CE_Failure or CE_Fatal.
err_no the error number (CPLE_*) from cpl_error.h.
fmt a printf() style format string. Any additional arguments will be treated as arguments to fill in this format in a manner similar to printf().
Since:
GDAL 1.9.0
CPLErr GDALRasterBand::SetCategoryNames ( char **  papszNames  )  [virtual]

Set the category names for this band.

See the GetCategoryNames() method for more on the interpretation of category names.

This method is the same as the C function GDALSetRasterCategoryNames().

Parameters:
papszNames the NULL terminated StringList of category names. May be NULL to just clear the existing list.
Returns:
CE_None on success of CE_Failure on failure. If unsupported by the driver CE_Failure is returned, but no error message is reported.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

CPLErr GDALRasterBand::SetColorInterpretation ( GDALColorInterp  eColorInterp  )  [virtual]

Set color interpretation of a band.

This method is the same as the C function GDALSetRasterColorInterpretation().

Parameters:
eColorInterp the new color interpretation to apply to this band.
Returns:
CE_None on success or CE_Failure if method is unsupported by format.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

CPLErr GDALRasterBand::SetColorTable ( GDALColorTable poCT  )  [virtual]

Set the raster color table.

The driver will make a copy of all desired data in the colortable. It remains owned by the caller after the call.

This method is the same as the C function GDALSetRasterColorTable().

Parameters:
poCT the color table to apply. This may be NULL to clear the color table (where supported).
Returns:
CE_None on success, or CE_Failure on failure. If the action is unsupported by the driver, a value of CE_Failure is returned, but no error is issued.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

CPLErr GDALRasterBand::SetDefaultHistogram ( double  dfMin,
double  dfMax,
int  nBuckets,
int *  panHistogram 
) [virtual]

Set default histogram.

This method is the same as the C function GDALSetDefaultHistogram().

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

CPLErr GDALRasterBand::SetDefaultRAT ( const GDALRasterAttributeTable poRAT  )  [virtual]

Set default Raster Attribute Table.

Associates a default RAT with the band. If not implemented for the format a CPLE_NotSupported error will be issued. If successful a copy of the RAT is made, the original remains owned by the caller.

This method is the same as the C function GDALSetDefaultRAT().

Parameters:
poRAT the RAT to assign to the band.
Returns:
CE_None on success or CE_Failure if unsupported or otherwise failing.

Reimplemented in GDALPamRasterBand, and GDALProxyRasterBand.

CPLErr GDALRasterBand::SetNoDataValue ( double  dfNoData  )  [virtual]

Set the no data value for this band.

To clear the nodata value, just set it with an "out of range" value. Complex band no data values must have an imagery component of zero.

This method is the same as the C function GDALSetRasterNoDataValue().

Parameters:
dfNoData the value to set.
Returns:
CE_None on success, or CE_Failure on failure. If unsupported by the driver, CE_Failure is returned by no error message will have been emitted.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

CPLErr GDALRasterBand::SetOffset ( double  dfNewOffset  )  [virtual]

Set scaling offset.

Very few formats implement this method. When not implemented it will issue a CPLE_NotSupported error and return CE_Failure.

This method is the same as the C function GDALSetRasterOffset().

Parameters:
dfNewOffset the new offset.
Returns:
CE_None or success or CE_Failure on failure.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

CPLErr GDALRasterBand::SetScale ( double  dfNewScale  )  [virtual]

Set scaling ratio.

Very few formats implement this method. When not implemented it will issue a CPLE_NotSupported error and return CE_Failure.

This method is the same as the C function GDALSetRasterScale().

Parameters:
dfNewScale the new scale.
Returns:
CE_None or success or CE_Failure on failure.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

CPLErr GDALRasterBand::SetStatistics ( double  dfMin,
double  dfMax,
double  dfMean,
double  dfStdDev 
) [virtual]

Set statistics on band.

This method can be used to store min/max/mean/standard deviation statistics on a raster band.

The default implementation stores them as metadata, and will only work on formats that can save arbitrary metadata. This method cannot detect whether metadata will be properly saved and so may return CE_None even if the statistics will never be saved.

This method is the same as the C function GDALSetRasterStatistics().

Parameters:
dfMin minimum pixel value.
dfMax maximum pixel value.
dfMean mean (average) of all pixel values.
dfStdDev Standard deviation of all pixel values.
Returns:
CE_None on success or CE_Failure on failure.

Reimplemented in GDALProxyRasterBand.

CPLErr GDALRasterBand::SetUnitType ( const char *  pszNewValue  )  [virtual]

Set unit type.

Set the unit type for a raster band. Values should be one of "" (the default indicating it is unknown), "m" indicating meters, or "ft" indicating feet, though other nonstandard values are allowed.

This method is the same as the C function GDALSetRasterUnitType().

Parameters:
pszNewValue the new unit type value.
Returns:
CE_None on success or CE_Failure if not succuessful, or unsupported.

Reimplemented in GDALPamRasterBand, GDALProxyRasterBand, and VRTRasterBand.

GDALRasterBlock * GDALRasterBand::TryGetLockedBlockRef ( int  nXBlockOff,
int  nYBlockOff 
) [protected]

Try fetching block ref.

This method will returned the requested block (locked) if it is already in the block cache for the layer. If not, NULL is returned.

If a non-NULL value is returned, then a lock for the block will have been acquired on behalf of the caller. It is absolutely imperative that the caller release this lock (with GDALRasterBlock::DropLock()) or else severe problems may result.

Parameters:
nXBlockOff the horizontal block offset, with zero indicating the left most block, 1 the next block and so forth.
nYBlockOff the vertical block offset, with zero indicating the top most block, 1 the next block and so forth.
Returns:
NULL if block not available, or locked block pointer.
CPLErr GDALRasterBand::WriteBlock ( int  nXBlockOff,
int  nYBlockOff,
void *  pImage 
)

Write a block of image data efficiently.

This method accesses a "natural" block from the raster band without resampling, or data type conversion. For a more generalized, but potentially less efficient access use RasterIO().

This method is the same as the C GDALWriteBlock() function.

See ReadBlock() for an example of block oriented data access.

Parameters:
nXBlockOff the horizontal block offset, with zero indicating the left most block, 1 the next block and so forth.
nYBlockOff the vertical block offset, with zero indicating the left most block, 1 the next block and so forth.
pImage the buffer from which the data will be written. The buffer must be large enough to hold GetBlockXSize()*GetBlockYSize() words of type GetRasterDataType().
Returns:
CE_None on success or CE_Failure on an error.

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

Generated for GDAL by doxygen 1.7.1.