DisplayFunction.h

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//     ____   ______ __
//    / __ \ / ____// /
//   / /_/ // /    / /
//  / ____// /___ / /___   PixInsight Class Library
// /_/     \____//_____/   PCL 2.6.5
// ----------------------------------------------------------------------------
// pcl/DisplayFunction.h - Released 2024-01-13T15:47:58Z
// ----------------------------------------------------------------------------
// This file is part of the PixInsight Class Library (PCL).
// PCL is a multiplatform C++ framework for development of PixInsight modules.
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// ----------------------------------------------------------------------------
 
#ifndef __PCL_DisplayFunction_h
#define __PCL_DisplayFunction_h
 
 
#include <pcl/Defs.h>
#include <pcl/Diagnostics.h>
 
#include <pcl/HistogramTransformation.h>
#include <pcl/Vector.h>
 
namespace pcl
{
 
// ----------------------------------------------------------------------------
 
/*
 * Default clipping increment in sigma units.
 */
#define __PCL_AUTOSTRETCH_DEFAULT_CLIP   -2.80
 
/*
 * Default target mean background in the [0,1] range.
 */
#define __PCL_AUTOSTRETCH_DEFAULT_TBGD    0.25
 
/*
 * Whether to apply a single transformation to nominal RGB channels, or
 * separate per-channel transformations.
 */
#define __PCL_AUTOSTRETCH_DEFAULT_LINK    false
 
// ----------------------------------------------------------------------------
 
class PCL_CLASS DisplayFunction : public ImageTransformation
{
public:
 
   DisplayFunction()
      : m_m( 4 ), m_s( 4 ), m_h( 4 ), m_l( 4 ), m_r( 4 )
   {
      Reset();
   }
 
   template <class V>
   DisplayFunction( const V& m, const V& s, const V& h, const V& l = V(), const V& r = V() )
      : m_m( 4 ), m_s( 4 ), m_h( 4 ), m_l( 4 ), m_r( 4 )
   {
      Reset();
      for ( int i = 0; i < 4 && i < int( m.Length() ); ++i ) m_m[i] = Range( double( m[i] ), 0.0, 1.0 );
      for ( int i = 0; i < 4 && i < int( s.Length() ); ++i ) m_s[i] = Range( double( s[i] ), 0.0, 1.0 );
      for ( int i = 0; i < 4 && i < int( h.Length() ); ++i ) m_h[i] = Range( double( h[i] ), 0.0, 1.0 );
      for ( int i = 0; i < 4 && i < int( l.Length() ); ++i ) m_l[i] = Max( 0.0, double( l[i] ) );
      for ( int i = 0; i < 4 && i < int( r.Length() ); ++i ) m_r[i] = Min( 1.0, double( r[i] ) );
      for ( int i = 0; i < 4; ++i )
         if ( m_h[i] < m_s[i] )
            pcl::Swap( m_s[i], m_h[i] );
   }
 
   DisplayFunction( const DisplayFunction& ) = default;
 
   DisplayFunction( DisplayFunction&& ) = default;
 
   DisplayFunction& operator =( const DisplayFunction& ) = default;
 
   DisplayFunction& operator =( DisplayFunction&& ) = default;
 
   ~DisplayFunction() override
   {
   }
 
   HistogramTransformation operator []( int i ) const
   {
      PCL_PRECONDITION( 0 <= i && i < 4 )
      PCL_CHECK( m_m.Length() == 4 && m_s.Length() == 4 && m_h.Length() == 4 && m_l.Length() == 4 && m_r.Length() == 4 )
      if ( i >= 0 && i < 4 )
         return HistogramTransformation( m_m[i], m_s[i], m_h[i], m_l[i], m_r[i] );
      return HistogramTransformation();
   }
 
   Array<HistogramTransformation> HistogramTransformations() const
   {
      return Array<HistogramTransformation>() << operator[]( 0 )
                                              << operator[]( 1 )
                                              << operator[]( 2 )
                                              << operator[]( 3 );
   }
 
   template <class V>
   void GetDisplayFunctionParameters( V& m, V& s, V& h, V& l, V& r ) const
   {
      m = m_m; s = m_s; h = m_h; l = m_l; r = m_r;
   }
 
   bool IsIdentityTransformation( int i ) const
   {
      PCL_PRECONDITION( 0 <= i && i < 4 )
      PCL_CHECK( m_m.Length() == 4 && m_s.Length() == 4 && m_h.Length() == 4 && m_l.Length() == 4 && m_r.Length() == 4 )
      return i >= 0 && i < 4 && m_m[i] == 0.5 && m_s[i] == 0 && m_h[i] == 1 && m_l[i] == 0 && m_r[i] == 1;
   }
 
   bool IsIdentityTransformation() const
   {
      return IsIdentityTransformation( 0 )
          && IsIdentityTransformation( 1 )
          && IsIdentityTransformation( 2 )
          && IsIdentityTransformation( 3 );
   }
 
   double ClippingPoint() const
   {
      return m_clip;
   }
 
   void SetClippingPoint( double clip )
   {
      m_clip = clip;
   }
 
   double TargetBackground() const
   {
      return m_tbkg;
   }
 
   /*
    * Sets the target background parameter of this transformation in the
    * normalized [0,1] range. The default target background is 0.25.
    */
   void SetTargetBackground( double tbkg )
   {
      m_tbkg = Range( tbkg, 0.0, 1.0 );
   }
 
   bool LinkedRGB() const
   {
      return m_link;
   }
 
   void SetLinkedRGB( bool link = true )
   {
      m_link = link;
   }
 
   template <class V>
   void ComputeAutoStretch( const V& sigma, const V& center )
   {
      PCL_CHECK( m_m.Length() == 4 && m_s.Length() == 4 && m_h.Length() == 4 && m_l.Length() == 4 && m_r.Length() == 4 )
 
      if ( sigma.IsEmpty() || center.IsEmpty() )
      {
         Reset();
         return;
      }
 
      int n = (sigma.Length() < 3 || center.Length() < 3) ? 1 : 3;
 
      if ( m_link )
      {
         /*
          * Try to find out how many channels look like channels of an inverted
          * image.
          *
          * We know a channel is inverted because the main histogram peak is
          * located over the right-hand half of the histogram. Seems simplistic
          * but this is consistent with most real-world images.
          */
         int invertedChannels = 0;
         for ( int i = 0; i < n; ++i )
            if ( center[i] > 0.5 )
               ++invertedChannels;
 
         double c = 0, m = 0;
         if ( invertedChannels < n )
         {
            // Noninverted image
            for ( int i = 0; i < n; ++i )
            {
               if ( 1 + sigma[i] != 1 )
                  c += center[i] + m_clip * sigma[i];
               m += center[i];
            }
            m_s[0] = m_s[1] = m_s[2] = Range( c/n, 0.0, 1.0 );
            m_m[0] = m_m[1] = m_m[2] = HistogramTransformation::MTF( m_tbkg, m/n - m_s[0] );
            m_l[0] = m_l[1] = m_l[2] = 0.0;
            m_h[0] = m_h[1] = m_h[2] = m_r[0] = m_r[1] = m_r[2] = 1.0;
         }
         else
         {
            // Inverted image
            for ( int i = 0; i < n; ++i )
            {
               c += (1 + sigma[i] != 1) ? center[i] - m_clip * sigma[i] : 1.0;
               m  += center[i];
            }
            m_h[0] = m_h[1] = m_h[2] = Range( c/n, 0.0, 1.0 );
            m_m[0] = m_m[1] = m_m[2] = HistogramTransformation::MTF( m_h[0] - m/n, m_tbkg );
            m_s[0] = m_s[1] = m_s[2] = m_l[0] = m_l[1] = m_l[2] = 0.0;
            m_r[0] = m_r[1] = m_r[2] = 1.0;
         }
      }
      else
      {
         /*
          * Unlinked RGB/K channnels: Compute automatic stretch functions for
          * individual RGB/K channels separately.
          */
         for ( int i = 0; i < n; ++i )
            if ( center[i] < 0.5 )
            {
               // Noninverted channel
               m_s[i] = (1 + sigma[i] != 1) ? Range( center[i] + m_clip * sigma[i], 0.0, 1.0 ) : 0.0;
               m_m[i] = HistogramTransformation::MTF( m_tbkg, center[i] - m_s[i] );
               m_l[i] = 0.0;
               m_h[i] = m_r[i] = 1.0;
            }
            else
            {
               // Inverted channel
               m_h[i] = (1 + sigma[i] != 1) ? Range( center[i] - m_clip * sigma[i], 0.0, 1.0 ) : 1.0;
               m_m[i] = HistogramTransformation::MTF( m_h[i] - center[i], m_tbkg );
               m_s[i] = m_l[i] = 0.0;
               m_r[i] = 1.0;
            }
      }
   }
 
   void Reset()
   {
      m_m = 0.5;
      m_s = m_l = 0.0;
      m_h = m_r = 1.0;
   }
 
   friend void Swap( DisplayFunction& x, DisplayFunction& y )
   {
      pcl::Swap( x.m_m, y.m_m );
      pcl::Swap( x.m_s, y.m_s );
      pcl::Swap( x.m_h, y.m_h );
      pcl::Swap( x.m_l, y.m_l );
      pcl::Swap( x.m_r, y.m_r );
      pcl::Swap( x.m_clip, y.m_clip );
      pcl::Swap( x.m_tbkg, y.m_tbkg );
      pcl::Swap( x.m_link, y.m_link );
   }
 
private:
 
   DVector m_m;   // midtones balance
   DVector m_s;   // shadows clipping point
   DVector m_h;   // highlights clipping point
   DVector m_l;   // shadows dynamic range expansion
   DVector m_r;   // highlights dynamic range expansion
   double  m_clip = __PCL_AUTOSTRETCH_DEFAULT_CLIP; // auto-stretch clipping point
   double  m_tbkg = __PCL_AUTOSTRETCH_DEFAULT_TBGD; // auto-stretch target background
   bool    m_link = __PCL_AUTOSTRETCH_DEFAULT_LINK; // auto-stretch linked RGB
 
   /*
    * Display function transformation.
    */
   void Apply( pcl::Image& ) const override;
   void Apply( pcl::DImage& ) const override;
   void Apply( pcl::UInt8Image& ) const override;
   void Apply( pcl::UInt16Image& ) const override;
   void Apply( pcl::UInt32Image& ) const override;
};
 
// ----------------------------------------------------------------------------
 
} // pcl
 
#endif   // __PCL_DisplayFunction_h
 
// ----------------------------------------------------------------------------
// EOF pcl/DisplayFunction.h - Released 2024-01-13T15:47:58Z