This class compares two images pixel-by-pixel. It uses the following methods to ignore the difference between images: More...

#include <Image_Diff.hxx>

Inheritance diagram for Image_Diff:

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Public Member Functions
	Image_Diff ()
	An empty constructor. Init() should be called for initialization. More...

virtual	~Image_Diff ()
	Desctructor. More...

Standard_Boolean	Init (const Handle< Image_PixMap > &theImageRef, const Handle< Image_PixMap > &theImageNew, const Standard_Boolean theToBlackWhite=Standard_False)
	Initialize algorithm by two images. More...

Standard_Boolean	Init (const TCollection_AsciiString &theImgPathRef, const TCollection_AsciiString &theImgPathNew, const Standard_Boolean theToBlackWhite=Standard_False)
	Initialize algorithm by two images (will be loaded from files). More...

void	SetColorTolerance (const Standard_Real theTolerance)
	Color tolerance for equality check. Should be within range 0..1: Corresponds to a difference between white and black colors (maximum difference). By default, the tolerance is equal to 0 thus equality check will return false for any different colors. More...

Standard_Real	ColorTolerance () const
	Color tolerance for equality check. More...

void	SetBorderFilterOn (const Standard_Boolean theToIgnore)
	Sets taking into account (ignoring) a "border effect" on comparison of images. The border effect is caused by a border of shaded shapes in the viewer 3d. Triangles of this area are located at about 0 or 90 degrees to the user. Therefore, they deflect light differently according to implementation of a video card driver. This flag allows to detect such a "border" area and skip it from comparison of images. Filter turned OFF by default. More...

Standard_Boolean	IsBorderFilterOn () const
	Returns a flag of taking into account (ignoring) a border effect in comparison of images. More...

Standard_Integer	Compare ()
	Compares two images. It returns a number of different pixels (or groups of pixels). It returns -1 if algorithm not initialized before. More...

Standard_Boolean	SaveDiffImage (Image_PixMap &theDiffImage) const
	Saves a difference between two images as white pixels on black backgroud. More...

Standard_Boolean	SaveDiffImage (const TCollection_AsciiString &theDiffPath) const
	Saves a difference between two images as white pixels on black backgroud. More...

Public Member Functions inherited from Standard_Transient
	Standard_Transient ()
	Empty constructor. More...

	Standard_Transient (const Standard_Transient &)
	Copy constructor – does nothing. More...

Standard_Transient &	operator= (const Standard_Transient &)
	Assignment operator, needed to avoid copying reference counter. More...

virtual	~Standard_Transient ()
	Destructor must be virtual. More...

virtual void	Delete () const
	Memory deallocator for transient classes. More...

virtual const Handle_Standard_Type &	DynamicType () const
	Returns a type information object about this object. More...

Standard_Boolean	IsInstance (const Handle_Standard_Type &theType) const
	Returns a true value if this is an instance of Type. More...

Standard_Boolean	IsInstance (const Standard_CString theTypeName) const
	Returns a true value if this is an instance of TypeName. More...

Standard_Boolean	IsKind (const Handle_Standard_Type &theType) const
	Returns true if this is an instance of Type or an instance of any class that inherits from Type. Note that multiple inheritance is not supported by OCCT RTTI mechanism. More...

Standard_Boolean	IsKind (const Standard_CString theTypeName) const
	Returns true if this is an instance of TypeName or an instance of any class that inherits from TypeName. Note that multiple inheritance is not supported by OCCT RTTI mechanism. More...

virtual Handle_Standard_Transient	This () const
	Returns a Handle which references this object. Must never be called to objects created in stack. More...

Standard_Integer	GetRefCount () const
	Get the reference counter of this object. More...

Protected Types
typedef NCollection_List < TColStd_MapOfInteger * >	ListOfMapOfInteger

Protected Member Functions
Standard_Integer	ignoreBorderEffect ()
	Perform border filter algorithm. More...

void	releaseGroupsOfDiffPixels ()
	Release dynamically allocated memory. More...

Protected Attributes
Handle< Image_PixMap >	myImageRef
	reference image to compare (from) More...

Handle< Image_PixMap >	myImageNew
	new image to compare (to) More...

Standard_Real	myColorTolerance
	tolerance for equality check (0..1, 0 - any not equal, 1 - opposite colors) More...

Standard_Boolean	myIsBorderFilterOn
	perform algorithm with border effect filter More...

ListOfMapOfInteger	myGroupsOfDiffPixels

NCollection_Vector< Standard_Size >	myDiffPixels
	different pixels (position packed into integer) More...

TColStd_MapOfInteger	myLinearGroups

Detailed Description

This class compares two images pixel-by-pixel. It uses the following methods to ignore the difference between images:

Black/White comparison. It makes the images 2-colored before the comparison.
Equality with tolerance. Colors of two pixels are considered the same if the differnce of their color is less than a tolerance.
Border filter. The algorithm ignores alone independent pixels, which are different on both images, ignores the "border effect" - the difference caused by triangles located at angle about 0 or 90 degrees to the user.

Border filter ignores a difference in implementation of anti-aliasing and other effects on boundary of a shape. The triangles of a boundary zone are usually located so that their normals point aside the user (about 90 degree between the normal and the direction to the user's eye). Deflection of the light for such a triangle depends on implementation of the video driver. In order to skip this difference the following algorithm is used: a) "Different" pixels are groupped and checked on "one-pixel width line". indeed, the pixels may represent not a line, but any curve. But the width of this curve should be not more than a pixel. This group of pixels become a candidate to be ignored because of boundary effect. b) The group of pixels is checked on belonging to a "shape". Neighbour pixels are checked from the reference image. This test confirms a fact that the group of pixels belongs to a shape and represent a boundary of the shape. In this case the whole group of pixels is ignored (considered as same). Otherwise, the group of pixels may represent a geometrical curve in the viewer 3D and should be considered as "different".

References:

http://pdiff.sourceforge.net/ypg01.pdf
http://pdiff.sourceforge.net/metric.html
http://www.cs.ucf.edu/~sumant/publications/sig99.pdf
http://www.worldscientific.com/worldscibooks/10.1142/2641#t=toc (there is a list of articles and books in PDF format)

Member Typedef Documentation

typedef NCollection_List<TColStd_MapOfInteger* > Image_Diff::ListOfMapOfInteger

protected

Constructor & Destructor Documentation

Image_Diff::Image_Diff ( )

An empty constructor. Init() should be called for initialization.

virtual Image_Diff::~Image_Diff ( )

virtual

Desctructor.

Member Function Documentation

Standard_Real Image_Diff::ColorTolerance ( ) const

Color tolerance for equality check.

Standard_Integer Image_Diff::Compare ( )

Compares two images. It returns a number of different pixels (or groups of pixels). It returns -1 if algorithm not initialized before.

Standard_Integer Image_Diff::ignoreBorderEffect ( )

protected

Perform border filter algorithm.

Standard_Boolean Image_Diff::Init	(	const Handle< Image_PixMap > &	theImageRef,
		const Handle< Image_PixMap > &	theImageNew,
		const Standard_Boolean	theToBlackWhite = `Standard_False`
	)

Initialize algorithm by two images.

Returns: false if images has different or unsupported pixel format.

Standard_Boolean Image_Diff::Init	(	const TCollection_AsciiString &	theImgPathRef,
		const TCollection_AsciiString &	theImgPathNew,
		const Standard_Boolean	theToBlackWhite = `Standard_False`
	)

Initialize algorithm by two images (will be loaded from files).

Returns: false if images couldn't be opened or their format is unsupported.

Standard_Boolean Image_Diff::IsBorderFilterOn ( ) const

Returns a flag of taking into account (ignoring) a border effect in comparison of images.

void Image_Diff::releaseGroupsOfDiffPixels ( )

protected

Release dynamically allocated memory.

Standard_Boolean Image_Diff::SaveDiffImage ( Image_PixMap & theDiffImage ) const

Saves a difference between two images as white pixels on black backgroud.

Standard_Boolean Image_Diff::SaveDiffImage ( const TCollection_AsciiString & theDiffPath ) const

Saves a difference between two images as white pixels on black backgroud.

void Image_Diff::SetBorderFilterOn ( const Standard_Boolean theToIgnore )

Sets taking into account (ignoring) a "border effect" on comparison of images. The border effect is caused by a border of shaded shapes in the viewer 3d. Triangles of this area are located at about 0 or 90 degrees to the user. Therefore, they deflect light differently according to implementation of a video card driver. This flag allows to detect such a "border" area and skip it from comparison of images. Filter turned OFF by default.

void Image_Diff::SetColorTolerance ( const Standard_Real theTolerance )

Color tolerance for equality check. Should be within range 0..1: Corresponds to a difference between white and black colors (maximum difference). By default, the tolerance is equal to 0 thus equality check will return false for any different colors.

Field Documentation

Standard_Real Image_Diff::myColorTolerance

protected

tolerance for equality check (0..1, 0 - any not equal, 1 - opposite colors)

NCollection_Vector<Standard_Size> Image_Diff::myDiffPixels

protected

different pixels (position packed into integer)

ListOfMapOfInteger Image_Diff::myGroupsOfDiffPixels

protected

Handle< Image_PixMap > Image_Diff::myImageNew

protected

new image to compare (to)

Handle< Image_PixMap > Image_Diff::myImageRef

protected

reference image to compare (from)

Standard_Boolean Image_Diff::myIsBorderFilterOn

protected

perform algorithm with border effect filter

TColStd_MapOfInteger Image_Diff::myLinearGroups

protected

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

Image_Diff.hxx

Public Member Functions

Protected Types

Protected Member Functions

Protected Attributes

Detailed Description

Member Typedef Documentation

Constructor & Destructor Documentation

Member Function Documentation

Field Documentation