This class compares two images pixel-by-pixel. It uses the following methods to ignore the difference between images:
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| | Image_Diff () |
| | An empty constructor. Init() should be called for initialization.
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| | ~Image_Diff () override |
| | Destructor.
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| bool | Init (const occ::handle< Image_PixMap > &theImageRef, const occ::handle< Image_PixMap > &theImageNew, const bool theToBlackWhite=false) |
| | Initialize algorithm by two images.
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| bool | Init (const TCollection_AsciiString &theImgPathRef, const TCollection_AsciiString &theImgPathNew, const bool theToBlackWhite=false) |
| | Initialize algorithm by two images (will be loaded from files).
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| void | SetColorTolerance (const double 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.
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| double | ColorTolerance () const |
| | Color tolerance for equality check.
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| void | SetBorderFilterOn (const bool 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.
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| bool | IsBorderFilterOn () const |
| | Returns a flag of taking into account (ignoring) a border effect in comparison of images.
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| int | Compare () |
| | Compares two images. It returns a number of different pixels (or groups of pixels). It returns -1 if algorithm not initialized before.
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| bool | SaveDiffImage (Image_PixMap &theDiffImage) const |
| | Saves a difference between two images as white pixels on black background.
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| bool | SaveDiffImage (const TCollection_AsciiString &theDiffPath) const |
| | Saves a difference between two images as white pixels on black background.
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 Public Member Functions inherited from Standard_Transient |
| | Standard_Transient () |
| | Empty constructor.
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| | Standard_Transient (const Standard_Transient &) |
| | Copy constructor – does nothing.
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| Standard_Transient & | operator= (const Standard_Transient &) |
| | Assignment operator, needed to avoid copying reference counter.
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| virtual | ~Standard_Transient ()=default |
| | Destructor must be virtual.
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| virtual const opencascade::handle< Standard_Type > & | DynamicType () const |
| | Returns a type descriptor about this object.
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| bool | IsInstance (const opencascade::handle< Standard_Type > &theType) const |
| | Returns a true value if this is an instance of Type.
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| bool | IsInstance (const char *const theTypeName) const |
| | Returns a true value if this is an instance of TypeName.
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| bool | IsKind (const opencascade::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.
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| bool | IsKind (const char *const 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.
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| Standard_Transient * | This () const |
| | Returns non-const pointer to this object (like const_cast). For protection against creating handle to objects allocated in stack or call from constructor, it will raise exception Standard_ProgramError if reference counter is zero.
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| int | GetRefCount () const noexcept |
| | Get the reference counter of this object.
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| void | IncrementRefCounter () noexcept |
| | Increments the reference counter of this object. Uses relaxed memory ordering since incrementing only requires atomicity, not synchronization with other memory operations.
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| int | DecrementRefCounter () noexcept |
| | Decrements the reference counter of this object; returns the decremented value. Uses release ordering for the decrement to ensure all writes to the object are visible before the count reaches zero. An acquire fence is added only when the count reaches zero, ensuring proper synchronization before deletion. This is more efficient than using acq_rel for every decrement.
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| virtual void | Delete () const |
| | Memory deallocator for transient classes.
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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 difference 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 grouped 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)
1.10.0