Source/System/Image/Squish/OSGSquishRangefit.cpp

   1 /* -----------------------------------------------------------------------------
   2
   3         Copyright (c) 2006 Simon Brown                          si@sjbrown.co.uk
   4
   5         Permission is hereby granted, free of charge, to any person obtaining
   6         a copy of this software and associated documentation files (the
   7         "Software"), to deal in the Software without restriction, including
   8         without limitation the rights to use, copy, modify, merge, publish,
   9         distribute, sublicense, and/or sell copies of the Software, and to
  10         permit persons to whom the Software is furnished to do so, subject to
  11         the following conditions:
  12
  13         The above copyright notice and this permission notice shall be included
  14         in all copies or substantial portions of the Software.
  15
  16         THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  17         OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  18         MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  19         IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  20         CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  21         TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  22         SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23
  24    -------------------------------------------------------------------------- */
  25
  26 #include "rangefit.h"
  27 #include "colourset.h"
  28 #include "colourblock.h"
  29 #include <cfloat>
  30
  31 namespace osgsquish {
  32
  33 RangeFit::RangeFit( ColourSet const* colours, int flags )
  34   : ColourFit( colours, flags ),
  35     m_metric(),
  36     m_start(),
  37     m_end(),
  38     m_besterror(0.f)
  39 {
  40         // initialise the metric
  41         bool perceptual = ( ( m_flags & kColourMetricPerceptual ) != 0 );
  42         if( perceptual )
  43                 m_metric = Vec3( 0.2126f, 0.7152f, 0.0722f );
  44         else
  45                 m_metric = Vec3( 1.0f );
  46
  47         // initialise the best error
  48         m_besterror = FLT_MAX;
  49
  50         // cache some values
  51         int const count = m_colours->GetCount();
  52         Vec3 const* values = m_colours->GetPoints();
  53         float const* weights = m_colours->GetWeights();
  54
  55         // get the covariance matrix
  56         Sym3x3 covariance = ComputeWeightedCovariance( count, values, weights );
  57
  58         // compute the principle component
  59         Vec3 principle = ComputePrincipleComponent( covariance );
  60
  61         // get the min and max range as the codebook endpoints
  62         Vec3 start( 0.0f );
  63         Vec3 end( 0.0f );
  64         if( count > 0 )
  65         {
  66                 float min, max;
  67
  68                 // compute the range
  69                 start = end = values[0];
  70                 min = max = Dot( values[0], principle );
  71                 for( int i = 1; i < count; ++i )
  72                 {
  73                         float val = Dot( values[i], principle );
  74                         if( val < min )
  75                         {
  76                                 start = values[i];
  77                                 min = val;
  78                         }
  79                         else if( val > max )
  80                         {
  81                                 end = values[i];
  82                                 max = val;
  83                         }
  84                 }
  85         }
  86
  87         // clamp the output to [0, 1]
  88         Vec3 const one( 1.0f );
  89         Vec3 const zero( 0.0f );
  90         start = Min( one, Max( zero, start ) );
  91         end = Min( one, Max( zero, end ) );
  92
  93         // clamp to the grid and save
  94         Vec3 const grid( 31.0f, 63.0f, 31.0f );
  95         Vec3 const gridrcp( 1.0f/31.0f, 1.0f/63.0f, 1.0f/31.0f );
  96         Vec3 const half( 0.5f );
  97         m_start = Truncate( grid*start + half )*gridrcp;
  98         m_end = Truncate( grid*end + half )*gridrcp;
  99 }
 100
 101 void RangeFit::Compress3( void* block )
 102 {
 103         // cache some values
 104         int const count = m_colours->GetCount();
 105         Vec3 const* values = m_colours->GetPoints();
 106
 107         // create a codebook
 108         Vec3 codes[3];
 109         codes[0] = m_start;
 110         codes[1] = m_end;
 111         codes[2] = 0.5f*m_start + 0.5f*m_end;
 112
 113         // match each point to the closest code
 114         u8 closest[16];
 115         float error = 0.0f;
 116         for( int i = 0; i < count; ++i )
 117         {
 118                 // find the closest code
 119                 float dist = FLT_MAX;
 120                 int idx = 0;
 121                 for( int j = 0; j < 3; ++j )
 122                 {
 123                         float d = LengthSquared( m_metric*( values[i] - codes[j] ) );
 124                         if( d < dist )
 125                         {
 126                                 dist = d;
 127                                 idx = j;
 128                         }
 129                 }
 130
 131                 // save the index
 132                 closest[i] = u8(idx);
 133
 134                 // accumulate the error
 135                 error += dist;
 136         }
 137
 138         // save this scheme if it wins
 139         if( error < m_besterror )
 140         {
 141                 // remap the indices
 142                 u8 indices[16];
 143                 m_colours->RemapIndices( closest, indices );
 144
 145                 // save the block
 146                 WriteColourBlock3( m_start, m_end, indices, block );
 147
 148                 // save the error
 149                 m_besterror = error;
 150         }
 151 }
 152
 153 void RangeFit::Compress4( void* block )
 154 {
 155         // cache some values
 156         int const count = m_colours->GetCount();
 157         Vec3 const* values = m_colours->GetPoints();
 158
 159         // create a codebook
 160         Vec3 codes[4];
 161         codes[0] = m_start;
 162         codes[1] = m_end;
 163         codes[2] = ( 2.0f/3.0f )*m_start + ( 1.0f/3.0f )*m_end;
 164         codes[3] = ( 1.0f/3.0f )*m_start + ( 2.0f/3.0f )*m_end;
 165
 166         // match each point to the closest code
 167         u8 closest[16];
 168         float error = 0.0f;
 169         for( int i = 0; i < count; ++i )
 170         {
 171                 // find the closest code
 172                 float dist = FLT_MAX;
 173                 int idx = 0;
 174                 for( int j = 0; j < 4; ++j )
 175                 {
 176                         float d = LengthSquared( m_metric*( values[i] - codes[j] ) );
 177                         if( d < dist )
 178                         {
 179                                 dist = d;
 180                                 idx = j;
 181                         }
 182                 }
 183
 184                 // save the index
 185                 closest[i] = u8(idx);
 186
 187                 // accumulate the error
 188                 error += dist;
 189         }
 190
 191         // save this scheme if it wins
 192         if( error < m_besterror )
 193         {
 194                 // remap the indices
 195                 u8 indices[16];
 196                 m_colours->RemapIndices( closest, indices );
 197
 198                 // save the block
 199                 WriteColourBlock4( m_start, m_end, indices, block );
 200
 201                 // save the error
 202                 m_besterror = error;
 203         }
 204 }
 205
 206 } // namespace squish