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 // Created on: 2012-07-10
 // Created by: VRO
 // Copyright (c) 2012-2014 OPEN CASCADE SAS
 //
 // This file is part of Open CASCADE Technology software library.
 //
 // This library is free software; you can redistribute it and/or modify it under
 // the terms of the GNU Lesser General Public License version 2.1 as published
 // by the Free Software Foundation, with special exception defined in the file
 // OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
 // distribution for complete text of the license and disclaimer of any warranty.
 //
 // Alternatively, this file may be used under the terms of Open CASCADE
 // commercial license or contractual agreement.
 
 #ifndef Image_Diff_HeaderFile
 #define Image_Diff_HeaderFile
 
 #include <Image_PixMap.hxx>
 #include <TCollection_AsciiString.hxx>
 #include <TColStd_HPackedMapOfInteger.hxx>
 #include <NCollection_List.hxx>
 #include <NCollection_Vector.hxx>
 
 //! 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 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:
 //!     1. http://pdiff.sourceforge.net/ypg01.pdf
 //!     2. http://pdiff.sourceforge.net/metric.html
 //!     3. http://www.cs.ucf.edu/~sumant/publications/sig99.pdf
 //!     4. http://www.worldscientific.com/worldscibooks/10.1142/2641#t=toc (there is a list of articles and books in PDF format)
 
 class Image_Diff : public Standard_Transient
 {
 
 public:
 
   //! An empty constructor. Init() should be called for initialization.
   Standard_EXPORT Image_Diff();
 
   //! Destructor.
   Standard_EXPORT virtual ~Image_Diff();
 
   //! Initialize algorithm by two images.
   //! @return false if images has different or unsupported pixel format.
   Standard_EXPORT Standard_Boolean Init (const Handle(Image_PixMap)& theImageRef,
                                          const Handle(Image_PixMap)& theImageNew,
                                          const Standard_Boolean      theToBlackWhite = Standard_False);
 
   //! Initialize algorithm by two images (will be loaded from files).
   //! @return false if images couldn't be opened or their format is unsupported.
   Standard_EXPORT Standard_Boolean Init (const TCollection_AsciiString& theImgPathRef,
                                          const TCollection_AsciiString& theImgPathNew,
                                          const Standard_Boolean         theToBlackWhite = Standard_False);
 
   //! 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.
   void SetColorTolerance (const Standard_Real theTolerance) {  myColorTolerance = theTolerance; }
 
   //! Color tolerance for equality check.
   Standard_Real ColorTolerance() const { return myColorTolerance; }
 
   //! 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 SetBorderFilterOn (const Standard_Boolean theToIgnore) { myIsBorderFilterOn = theToIgnore; }
 
   //! Returns a flag of taking into account (ignoring) a border effect in comparison of images.
   Standard_Boolean IsBorderFilterOn() const { return myIsBorderFilterOn; }
 
   //! Compares two images. It returns a number of different pixels (or groups of pixels).
   //! It returns -1 if algorithm not initialized before.
   Standard_EXPORT Standard_Integer Compare();
 
   //! Saves a difference between two images as white pixels on black background.
   Standard_EXPORT Standard_Boolean SaveDiffImage (Image_PixMap& theDiffImage) const;
 
   //! Saves a difference between two images as white pixels on black background.
   Standard_EXPORT Standard_Boolean SaveDiffImage (const TCollection_AsciiString& theDiffPath) const;
 
 protected:
 
   //! Perform border filter algorithm.
   Standard_EXPORT Standard_Integer ignoreBorderEffect();
 
   //! Release dynamically allocated memory.
   Standard_EXPORT void releaseGroupsOfDiffPixels();
 
 protected:
 
   //! Map two pixel coordinates to 32-bit integer
   static Standard_Integer PackXY (uint16_t theX, uint16_t theY)
   {
     return Standard_Integer((unsigned int)theY | 
                            ((unsigned int)theX << 16));
   }
 
   //! Get pixel X coordinate from 32-bit packed integer
   static uint16_t UnpackX (Standard_Integer theXY)
   {
     return (uint16_t)(((unsigned int)theXY & 0xffff0000) >> 16);
   }
 
   //! Get pixel Y coordinate from 32-bit packed integer
   static uint16_t UnpackY (Standard_Integer theXY)
   {
     return (uint16_t)((unsigned int)theXY & 0xffff);
   }
 
 protected:
 
   Handle(Image_PixMap)              myImageRef;           //!< reference image to compare (from)
   Handle(Image_PixMap)              myImageNew;           //!< new       image to compare (to)
   Standard_Real                     myColorTolerance;     //!< tolerance for equality check (0..1, 0 - any not equal, 1 - opposite colors)
 
   Standard_Boolean                  myIsBorderFilterOn;   //!< perform algorithm with border effect filter
 
   //! coordinates of different pixels, packed in one int using 16-bit integers to save memory
   NCollection_Vector<Standard_Integer> myDiffPixels;
   TColStd_PackedMapOfInteger        myLinearGroups;
   NCollection_List<Handle(TColStd_HPackedMapOfInteger)>
                                     myGroupsOfDiffPixels;
 
 public:
 
   DEFINE_STANDARD_RTTIEXT(Image_Diff,Standard_Transient) // Type definition
 
 };
 
 DEFINE_STANDARD_HANDLE(Image_Diff, Standard_Transient)
 
 #endif // _Image_Diff_H__

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