virtualx-engine/drivers/squish/rangefit.cpp

/* -----------------------------------------------------------------------------

	Copyright (c) 2006 Simon Brown                          si@sjbrown.co.uk

	Permission is hereby granted, free of charge, to any person obtaining
	a copy of this software and associated documentation files (the 
	"Software"), to	deal in the Software without restriction, including
	without limitation the rights to use, copy, modify, merge, publish,
	distribute, sublicense, and/or sell copies of the Software, and to 
	permit persons to whom the Software is furnished to do so, subject to 
	the following conditions:

	The above copyright notice and this permission notice shall be included
	in all copies or substantial portions of the Software.

	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
	OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
	IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 
	CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 
	TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE 
	SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
	
   -------------------------------------------------------------------------- */
   
#include "rangefit.h"
#include "colourset.h"
#include "colourblock.h"
#include <cfloat>

namespace squish {

RangeFit::RangeFit( ColourSet const* colours, int flags ) 
  : ColourFit( colours, flags )
{
	// initialise the metric
	bool perceptual = ( ( m_flags & kColourMetricPerceptual ) != 0 );
	if( perceptual )
		m_metric = Vec3( 0.2126f, 0.7152f, 0.0722f );
	else
		m_metric = Vec3( 1.0f );

	// initialise the best error
	m_besterror = FLT_MAX;

	// cache some values
	int const count = m_colours->GetCount();
	Vec3 const* values = m_colours->GetPoints();
	float const* weights = m_colours->GetWeights();
	
	// get the covariance matrix
	Sym3x3 covariance = ComputeWeightedCovariance( count, values, weights );
	
	// compute the principle component
	Vec3 principle = ComputePrincipleComponent( covariance );

	// get the min and max range as the codebook endpoints
	Vec3 start( 0.0f );
	Vec3 end( 0.0f );
	if( count > 0 )
	{
		float min, max;
		
		// compute the range
		start = end = values[0];
		min = max = Dot( values[0], principle );
		for( int i = 1; i < count; ++i )
		{
			float val = Dot( values[i], principle );
			if( val < min )
			{
				start = values[i];
				min = val;
			}
			else if( val > max )
			{
				end = values[i];
				max = val;
			}
		}
	}
			
	// clamp the output to [0, 1]
	Vec3 const one( 1.0f );
	Vec3 const zero( 0.0f );
	start = Min( one, Max( zero, start ) );
	end = Min( one, Max( zero, end ) );

	// clamp to the grid and save
	Vec3 const grid( 31.0f, 63.0f, 31.0f );
	Vec3 const gridrcp( 1.0f/31.0f, 1.0f/63.0f, 1.0f/31.0f );
	Vec3 const half( 0.5f );
	m_start = Truncate( grid*start + half )*gridrcp;
	m_end = Truncate( grid*end + half )*gridrcp;
}

void RangeFit::Compress3( void* block )
{
	// cache some values
	int const count = m_colours->GetCount();
	Vec3 const* values = m_colours->GetPoints();
	
	// create a codebook
	Vec3 codes[3];
	codes[0] = m_start;
	codes[1] = m_end;
	codes[2] = 0.5f*m_start + 0.5f*m_end;

	// match each point to the closest code
	u8 closest[16];
	float error = 0.0f;
	for( int i = 0; i < count; ++i )
	{
		// find the closest code
		float dist = FLT_MAX;
		int idx = 0;
		for( int j = 0; j < 3; ++j )
		{
			float d = LengthSquared( m_metric*( values[i] - codes[j] ) );
			if( d < dist )
			{
				dist = d;
				idx = j;
			}
		}
		
		// save the index
		closest[i] = ( u8 )idx;
		
		// accumulate the error
		error += dist;
	}
	
	// save this scheme if it wins
	if( error < m_besterror )
	{
		// remap the indices
		u8 indices[16];
		m_colours->RemapIndices( closest, indices );
		
		// save the block
		WriteColourBlock3( m_start, m_end, indices, block );
		
		// save the error
		m_besterror = error;
	}
}

void RangeFit::Compress4( void* block )
{
	// cache some values
	int const count = m_colours->GetCount();
	Vec3 const* values = m_colours->GetPoints();
	
	// create a codebook
	Vec3 codes[4];
	codes[0] = m_start;
	codes[1] = m_end;
	codes[2] = ( 2.0f/3.0f )*m_start + ( 1.0f/3.0f )*m_end;
	codes[3] = ( 1.0f/3.0f )*m_start + ( 2.0f/3.0f )*m_end;

	// match each point to the closest code
	u8 closest[16];
	float error = 0.0f;
	for( int i = 0; i < count; ++i )
	{
		// find the closest code
		float dist = FLT_MAX;
		int idx = 0;
		for( int j = 0; j < 4; ++j )
		{
			float d = LengthSquared( m_metric*( values[i] - codes[j] ) );
			if( d < dist )
			{
				dist = d;
				idx = j;
			}
		}
		
		// save the index
		closest[i] = ( u8 )idx;
		
		// accumulate the error
		error += dist;
	}
	
	// save this scheme if it wins
	if( error < m_besterror )
	{
		// remap the indices
		u8 indices[16];
		m_colours->RemapIndices( closest, indices );
		
		// save the block
		WriteColourBlock4( m_start, m_end, indices, block );

		// save the error
		m_besterror = error;
	}
}

} // namespace squish