Abstract base class for ML data compression algorithms. More...

#include <mlDataCompressor.h>

Inheritance diagram for ml::DataCompressor:

Public Types
Constants.
enum	{ MaxHints = 10 }
	The maximum number of usable optional parameters for a compressor class derived from DataCompressor. More...

enum	HintType { Unused = 0 , IsDouble = 1 , IsInt = 2 , IsBool = 3 , IsString = 4 , IsDataType = 5 }
	Possible values to describe the type of a compression parameter. More...

Public Types inherited from ml::Base
enum	PersistenceInterface { PersistenceByString , PersistenceByTreeNode , PersistenceByStream }
	This enum describes the different persistence interfaces available. More...

Public Member Functions
Construction, destruction.
	DataCompressor ()
	Constructor.

	~DataCompressor () override
	Destructor.

Basic compressor description.
virtual std::string	getTypeName () const =0
	Returns the name of the compression scheme, used for example in user interfaces to select a compression scheme, something of the kind "ZLIB", "TIFF", or "PNG".

virtual std::string	getVersion () const =0
	Returns the version string.

virtual bool	isSupportedVersion (const std::string &ver) const =0
	Returns `true` if the passed version `ver` is supported by the implemented compressor class and `false` otherwise.

virtual std::string	getVendor () const
	Returns the name of the vendor providing the compressor code or algorithm, something of the kind "MeVis", the author or the company selling the algorithm.

virtual std::string	getSuffix () const
	Returns the suffix describing the compression scheme, for example "lzw", "tiff".

virtual bool	isLossy () const
	Returns `true` if compression is lossy, `false` if not.

Optional parameters that may be used by the derived compressor classes.
virtual MLDataType	getDataType () const
	Returns the data type of the compressed data or -1 if unknown. Default is -1.

virtual void	setDataType (MLDataType dt)
	Sets the data type of the compressed data or -1 if unknown. Default is -1.

virtual size_t	getVoxelSize () const
	Returns the size of one voxel or 1 if unknown. Default is 1.

virtual void	setVoxelSize (size_t vSize)
	Sets the size of one voxel or 1 if unknown. Default is 1.

virtual void	getImageExtent (MLint ext[6]) const
	Returns the extent of the compressed data chunk in voxels or [0,0,0] if unknown. Default is [0,0,0].

virtual void	setImageExtent (const MLint ext[6])
	Sets the size of one voxel or 1 if unknown. Default is 1.

virtual MLuint8	numUsedHints () const
	Returns the number of hints used by the derived compressor class, it defaults to 0.

virtual void	getHint (MLuint8 hintIdx, HintType &hintType, std::string &strVal, std::string &hintName, double &rangeMin, double &rangeMax) const
	Gets the optional parameters settings for different purposes.

virtual MLErrorCode	setHint (MLuint8 hintIdx, const std::string value)
	Sets the hint `value` of the hint number `hintIdx`.

virtual MLErrorCode	setHint (const std::string &hintName, const std::string &value)
	Sets the hint `value` of the hint given by the name `hintName`.

virtual int	findHint (const std::string &hintName)
	Returns the index of the hint with name `hintName` or -1 if not found.

Public Member Functions inherited from ml::Base
	Base ()
	Constructor.

virtual	~Base ()
	Destructor.

virtual Base *	deepCopy () const
	Creates a deep copy of the given object.

bool	isOfAllowedType (const std::vector< const RuntimeType * > &types) const
	Checks whether this object's type is equal to or derived from one of the types given in the argument.

virtual bool	isRefCountedBase () const
	Returns whether the instance is derived from RefCountedBase.

virtual std::string	detailString () const
	Returns a string describing this object.

virtual bool	implementsPersistence (PersistenceInterface) const
	Override this method to declare which persistence interfaces are implemented by your derived class.

virtual std::string	persistentState () const
	Returns a string describing the object's internal state.

virtual void	setPersistentState (const std::string &state)
	Restores the object's internal state from a string that had been previously generated using persistentState().

virtual void	addStateToTree (TreeNode *) const
	Attaches the object state as children of the given parent node.

virtual void	readStateFromTree (TreeNode *)
	Reads the object state from the children of the given parent node.

virtual void	writeTo (AbstractPersistenceOutputStream *) const
	Writes the objects state to the data stream object.

virtual void	readFrom (AbstractPersistenceInputStream *, int)
	Reads the objects state from the data stream object.

Static Protected Member Functions
Data reorganization for better compression ratios.
static int	reorderBytePlanes (void *data, size_t dataSize, size_t voxSize)
	Prepares the data for optimal compression, returns 0 on success, and a non-zero value otherwise.

static int	unReorderBytePlanes (void *data, size_t dataSize, size_t voxSize)
	Makes data preparation undone, returns 0 on success, and a non-zero value otherwise.

static void	diffCodeData (void *data, size_t dataSize, size_t voxSize=1)
	This tool recodes a data array by calculating a coded difference between each voxel and its next voxel, replacing the next voxel with its coded difference.

static void	undiffCodeData (void *data, size_t dataSize, size_t voxSize=1)
	See diffCodeData for the inverse operation and documentation.

static int	reorderDataTraversal (void *data, size_t dataSize, size_t voxSize, const MLint64 imgExt[6])
	Reorders the traversal of the data to use local data coherence, reducing changes between neighboring voxels, which often improves compression.

static int	unReorderDataTraversal (void *data, size_t dataSize, size_t voxSize, const MLint64 imgExt[6])
	Undoes the operation applied by reorderDataTraversal, for further information see reorderDataTraversal.

static void	packMLints (const MLint vec[6], unsigned char packedBuffer[55])
	Packs six MLint values if possible to a smaller memory.

static void	unpackMLints (const unsigned char packedBuffer[55], MLint vec[6])
	Inverse operation to packMLints.

Protected Attributes
Arrays of optional compressor parameters that may be changed by derived classes.
HintType	_hintType [MaxHints]
	Type of the optional parameter, default is Unused.

std::string	_strHints [MaxHints]
	Array for optional string hints, default is "".

std::string	_hintName [MaxHints]
	Array for optional string hints, default is "".

double	_rangeMin [MaxHints]
	Minimum interval range for numeric parameter, default is 0.

double	_rangeMax [MaxHints]
	Maximum interval range for numeric parameter, default is 0.

Compression and decompression
MLDataType	_dataType
	Data type that can be specified by some applications, default is -1 if unknown.

size_t	_voxelSize
	Data type that can be specified by some applications, default is 1 if unknown.

MLint	_ext [6]
	Extent of the compressed data chunk in voxels, default is [0,0,0,0,0,0] if unknown.

virtual MLErrorCode	compress (const void srcMem, size_t srcSize, void &dstMem, MLint &dstNum) const =0
	Compresses a chunk of memory.

virtual MLErrorCode	decompress (const void srcMem, size_t srcSize, void &dstMem, MLint64 &resSize) const =0
	Uncompresses a chunk of memory.

Detailed Description

Abstract base class for ML data compression algorithms.

See MLDataCompressorDoc.h for further information.

Definition at line 36 of file mlDataCompressor.h.

Member Enumeration Documentation

◆ anonymous enum

anonymous enum

The maximum number of usable optional parameters for a compressor class derived from DataCompressor.

Default is 0.

Enumerator
MaxHints

Definition at line 47 of file mlDataCompressor.h.

◆ HintType

enum ml::DataCompressor::HintType

Possible values to describe the type of a compression parameter.

Enumerator
Unused	Default value: The parameters is not used.
IsDouble	The parameter is a double parameter.
IsInt	The parameter is an integer parameter.
IsBool	The integer is `false` if 0, `true` otherwise.
IsString	The parameter is a string parameter.
IsDataType	The integer represents an MLDataType or -1 if not valid.

Definition at line 50 of file mlDataCompressor.h.

Constructor & Destructor Documentation

◆ DataCompressor()

ml::DataCompressor::DataCompressor ( )

Constructor.

◆ ~DataCompressor()

ml::DataCompressor::~DataCompressor ( )

override

Destructor.

Member Function Documentation

◆ compress()

virtual MLErrorCode ml::DataCompressor::compress	(	const void *	srcMem,
		size_t	srcSize,
		void *&	dstMem,
		MLint &	dstNum ) const

pure virtual

Compresses a chunk of memory.

Assumes the data to be aligned on voxel size borders.

Parameters

srcMem	The pointer of data to be compressed.
srcSize	The size of the data pointed to by srcMem in bytes.
dstMem	Returns the pointer to the compressed data. The compressor will allocate the required memory and overwrite the dstMem pointer, which must be freed by the caller with MLFree() or Memory::freeMemory().
dstNum	Will be set to size of the compressed data chunk in bytes or to 0 on error.

Returns: ML_RESULT_OK on successful compression or an error code describing the error.

◆ decompress()

virtual MLErrorCode ml::DataCompressor::decompress	(	const void *	srcMem,
		size_t	srcSize,
		void *&	dstMem,
		MLint64 &	resSize ) const

pure virtual

Uncompresses a chunk of memory.

Assumes the data to be aligned on voxel size borders.

Parameters

srcMem	The pointer to the compressed data to be uncompressed.
srcSize	The size of the data pointed to by srcMem in bytes.
dstMem	Returns the pointer to the uncompressed data. The dstMem pointer is overwritten with the pointer to the allocated uncompressed data, which must be freed by the caller with MLFree() or Memory::freeMemory().
resSize	Returns the size of the uncompressed data memory in bytes or 0 on error.

Returns: ML_RESULT_OK on successful decompression or an error code describing the error.

◆ diffCodeData()

static void ml::DataCompressor::diffCodeData	(	void *	data,
		size_t	dataSize,
		size_t	voxSize = 1 )

staticprotected

This tool recodes a data array by calculating a coded difference between each voxel and its next voxel, replacing the next voxel with its coded difference.

The coded difference is the absolute integer difference between both values, with the sign bit stored in the first bit. Image data coded in this way can be compressed better by many types of compressors, often improving compression ratios. See also undiffCodeData for restoring the original data.

Parameters

data	The pointer to the data chunk to be recoded. The call is ignored if data is NULL.
dataSize	The number of bytes of in data. The call is ignored if dataSize is <2.
voxSize	The word size of data (for example, 2 for short data, 4 for integer data). Giving correct data type sizes as voxSizes usually improves compressibility. For values < 1 or values other than 1,2, 4, or 8, the call is ignored. If the dataSize is not divisible by voxSize, the remaining bytes are not coded but left unchanged. Assumes the data to be aligned on voxel size borders.

◆ findHint()

virtual int ml::DataCompressor::findHint ( const std::string & hintName )

virtual

Returns the index of the hint with name hintName or -1 if not found.

◆ getDataType()

virtual MLDataType ml::DataCompressor::getDataType ( ) const

inlinevirtual

Returns the data type of the compressed data or -1 if unknown. Default is -1.

Definition at line 117 of file mlDataCompressor.h.

◆ getHint()

virtual void ml::DataCompressor::getHint	(	MLuint8	hintIdx,
		HintType &	hintType,
		std::string &	strVal,
		std::string &	hintName,
		double &	rangeMin,
		double &	rangeMax ) const

virtual

Gets the optional parameters settings for different purposes.

◆ getImageExtent()

virtual void ml::DataCompressor::getImageExtent ( MLint ext[6] ) const

inlinevirtual

Returns the extent of the compressed data chunk in voxels or [0,0,0] if unknown. Default is [0,0,0].

Definition at line 131 of file mlDataCompressor.h.

References mlrange_cast().

◆ getSuffix()

virtual std::string ml::DataCompressor::getSuffix ( ) const

inlinevirtual

Returns the suffix describing the compression scheme, for example "lzw", "tiff".

Definition at line 100 of file mlDataCompressor.h.

◆ getTypeName()

virtual std::string ml::DataCompressor::getTypeName ( ) const

pure virtual

Returns the name of the compression scheme, used for example in user interfaces to select a compression scheme, something of the kind "ZLIB", "TIFF", or "PNG".

◆ getVendor()

virtual std::string ml::DataCompressor::getVendor ( ) const

inlinevirtual

Returns the name of the vendor providing the compressor code or algorithm, something of the kind "MeVis", the author or the company selling the algorithm.

Definition at line 96 of file mlDataCompressor.h.

◆ getVersion()

virtual std::string ml::DataCompressor::getVersion ( ) const

pure virtual

Returns the version string.

The compression class itself must provide checks for compatibility with version handling methods, something of the kind "1.1.4" or "1.1".

◆ getVoxelSize()

virtual size_t ml::DataCompressor::getVoxelSize ( ) const

inlinevirtual

Returns the size of one voxel or 1 if unknown. Default is 1.

Definition at line 124 of file mlDataCompressor.h.

◆ isLossy()

virtual bool ml::DataCompressor::isLossy ( ) const

inlinevirtual

Returns true if compression is lossy, false if not.

Default is false. Returns true if the uncompress method does not restore the data identically, as otherwise, other classes will detect checksum errors on that data. If the data is restored identically, it should return false to have those security checks enabled.

Definition at line 107 of file mlDataCompressor.h.

◆ isSupportedVersion()

virtual bool ml::DataCompressor::isSupportedVersion ( const std::string & ver ) const

pure virtual

Returns true if the passed version ver is supported by the implemented compressor class and false otherwise.

◆ numUsedHints()

virtual MLuint8 ml::DataCompressor::numUsedHints ( ) const

inlinevirtual

Returns the number of hints used by the derived compressor class, it defaults to 0.

Definition at line 138 of file mlDataCompressor.h.

◆ packMLints()

static void ml::DataCompressor::packMLints	(	const MLint	vec[6],
		unsigned char	packedBuffer[55] )

staticprotected

Packs six MLint values if possible to a smaller memory.

This is useful if, for example, an image extent has to be stored in compressed data data, as on small data blocks six MLint values need considerable data size (48 bytes). The maximum result size is 55 bytes.

◆ reorderBytePlanes()

static int ml::DataCompressor::reorderBytePlanes	(	void *	data,
		size_t	dataSize,
		size_t	voxSize )

staticprotected

Prepares the data for optimal compression, returns 0 on success, and a non-zero value otherwise.

Depending on voxSize, the lowest bytes are stored first, then medium,.... up to the highest bytes last. Using this function can especially be useful to prepare data for compression algorithms that have better compression ratios on bytes streams of values, for example, of type 0 0 0 0 321 554 12 37 than on byte streams of type 0 321 0 554 0 12 0 37. This often holds true for some text or stream compressors types (lzw, bzip2, zlib). Of course, this also depends on the type of data and is mostly used only optionally, as data reordering also costs additional performance and also degrades compression efficiency in some cases. Assumes the data to be aligned on voxel size borders.

◆ reorderDataTraversal()

static int ml::DataCompressor::reorderDataTraversal	(	void *	data,
		size_t	dataSize,
		size_t	voxSize,
		const MLint64	imgExt[6] )

staticprotected

Reorders the traversal of the data to use local data coherence, reducing changes between neighboring voxels, which often improves compression.

Returns >= 0 on success or no operation, and values < 0 on errors. It reorders the data only if voxSize is in [1,2,4,8]. Voxel sizes > 8 are allowed but ignored, with a return value of 1. Return values: -3 : Out of memory error, nothing done. -2 : Error, bad parameter. -1 : Unspecific error or crash. <0 : Error 0 : Data has been successfully reordered. 1 : Nothing done and no error. Assumes the data to be aligned on voxel size borders.

◆ setDataType()

virtual void ml::DataCompressor::setDataType ( MLDataType dt )

inlinevirtual

Sets the data type of the compressed data or -1 if unknown. Default is -1.

Definition at line 120 of file mlDataCompressor.h.

References mlrange_cast().

◆ setHint() [1/2]

virtual MLErrorCode ml::DataCompressor::setHint	(	const std::string &	hintName,
		const std::string &	value )

virtual

Sets the hint value of the hint given by the name hintName.

Returns ML_RESULT_OK on success and on failure, returns a code describing the problem.

◆ setHint() [2/2]

virtual MLErrorCode ml::DataCompressor::setHint	(	MLuint8	hintIdx,
		const std::string	value )

virtual

Sets the hint value of the hint number hintIdx.

Returns ML_RESULT_OK on success and on failure, returns a code describing the problem.

◆ setImageExtent()

virtual void ml::DataCompressor::setImageExtent ( const MLint ext[6] )

inlinevirtual

Sets the size of one voxel or 1 if unknown. Default is 1.

Definition at line 134 of file mlDataCompressor.h.

References mlrange_cast().

◆ setVoxelSize()

virtual void ml::DataCompressor::setVoxelSize ( size_t vSize )

inlinevirtual

Sets the size of one voxel or 1 if unknown. Default is 1.

Definition at line 127 of file mlDataCompressor.h.

References mlrange_cast().

◆ undiffCodeData()

static void ml::DataCompressor::undiffCodeData	(	void *	data,
		size_t	dataSize,
		size_t	voxSize = 1 )

staticprotected

See diffCodeData for the inverse operation and documentation.

Assumes the data to be aligned on voxel size borders.

◆ unpackMLints()

static void ml::DataCompressor::unpackMLints	(	const unsigned char	packedBuffer[55],
		MLint	vec[6] )

staticprotected

Inverse operation to packMLints.

◆ unReorderBytePlanes()

static int ml::DataCompressor::unReorderBytePlanes	(	void *	data,
		size_t	dataSize,
		size_t	voxSize )

staticprotected

Makes data preparation undone, returns 0 on success, and a non-zero value otherwise.

See reorderBytePlanes for further information. Assumes the data to be aligned on voxel size borders.

◆ unReorderDataTraversal()

static int ml::DataCompressor::unReorderDataTraversal	(	void *	data,
		size_t	dataSize,
		size_t	voxSize,
		const MLint64	imgExt[6] )

staticprotected

Undoes the operation applied by reorderDataTraversal, for further information see reorderDataTraversal.

Assumes the data to be aligned on voxel size borders.

Member Data Documentation

◆ _dataType

MLDataType ml::DataCompressor::_dataType

protected

Data type that can be specified by some applications, default is -1 if unknown.

Definition at line 214 of file mlDataCompressor.h.

◆ _ext

MLint ml::DataCompressor::_ext[6]

protected

Extent of the compressed data chunk in voxels, default is [0,0,0,0,0,0] if unknown.

Definition at line 220 of file mlDataCompressor.h.

◆ _hintName

std::string ml::DataCompressor::_hintName[MaxHints]

protected

Array for optional string hints, default is "".

Definition at line 232 of file mlDataCompressor.h.

◆ _hintType

HintType ml::DataCompressor::_hintType[MaxHints]

protected

Type of the optional parameter, default is Unused.

Definition at line 226 of file mlDataCompressor.h.

◆ _rangeMax

double ml::DataCompressor::_rangeMax[MaxHints]

protected

Maximum interval range for numeric parameter, default is 0.

Definition at line 238 of file mlDataCompressor.h.

◆ _rangeMin

double ml::DataCompressor::_rangeMin[MaxHints]

protected

Minimum interval range for numeric parameter, default is 0.

Definition at line 235 of file mlDataCompressor.h.

◆ _strHints

std::string ml::DataCompressor::_strHints[MaxHints]

protected

Array for optional string hints, default is "".

Definition at line 229 of file mlDataCompressor.h.

◆ _voxelSize

size_t ml::DataCompressor::_voxelSize

protected

Data type that can be specified by some applications, default is 1 if unknown.

Definition at line 217 of file mlDataCompressor.h.

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

MeVis/Foundation/Sources/MLDataCompressors/MLDataCompressor/mlDataCompressor.h

Public Types

Public Member Functions

Static Protected Member Functions

Protected Attributes

Compression and decompression

Detailed Description

Member Enumeration Documentation

◆ anonymous enum

◆ HintType

Constructor & Destructor Documentation

◆ DataCompressor()

◆ ~DataCompressor()

Member Function Documentation

◆ compress()

◆ decompress()

◆ diffCodeData()

◆ findHint()

◆ getDataType()

◆ getHint()

◆ getImageExtent()

◆ getSuffix()

◆ getTypeName()

◆ getVendor()

◆ getVersion()

◆ getVoxelSize()

◆ isLossy()

◆ isSupportedVersion()

◆ numUsedHints()

◆ packMLints()

◆ reorderBytePlanes()

◆ reorderDataTraversal()

◆ setDataType()

◆ setHint() [1/2]

◆ setHint() [2/2]

◆ setImageExtent()

◆ setVoxelSize()

◆ undiffCodeData()

◆ unpackMLints()

◆ unReorderBytePlanes()

◆ unReorderDataTraversal()

Member Data Documentation

◆ _dataType

◆ _ext

◆ _hintName

◆ _hintType

◆ _rangeMax

◆ _rangeMin

◆ _strHints

◆ _voxelSize