nvidia-texture-tools/extern/libsquish-1.15/extra/squishgen.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 <iostream>

struct SourceBlock
{
    int start;
    int end;
    int error;
};

struct TargetValue
{
    SourceBlock sources[2];
};

static void GenerateData( std::string const& name, int bits, int colours )
{
    TargetValue values[256];

    // initialise the data
    for( int target = 0; target < 256; ++target )
        for( int index = 0; index < colours; ++index )
            values[target].sources[index].error = 255;

    // loop over all possible source points
    int count = ( 1 << bits );
    for( int value1 = 0; value1 < count; ++value1 )
    {
        for( int value2 = 0; value2 < count; ++value2 )
        {
            // compute the 8-bit endpoints
            int a = ( value1 << ( 8 - bits ) ) | ( value1 >> ( 2*bits - 8 ) );
            int b = ( value2 << ( 8 - bits ) ) | ( value2 >> ( 2*bits - 8 ) );

            // fill in the codebook with the these and intermediates
            int codes[2];
            codes[0] = a;
            if( colours == 3 )
                codes[1] = ( a + b )/2;
            else
                codes[1] = ( 2*a + b )/3;

            // mark each target point with the endpoints and index needed for it
            for( int index = 0; index < 2; ++index )
            {
                int target = codes[index];

                SourceBlock& block = values[target].sources[index];
                if( block.error != 0 )
                {
                    block.start = value1;
                    block.end = value2;
                    block.error = 0;
                }
            }
        }
    }

    // iteratively fill in the missing values
    for( ;; )
    {
        bool stable = true;
        for( int index = 0; index < 2; ++index )
        {
            for( int target = 0; target < 256; ++target )
            {
                if( target != 255 )
                {
                    SourceBlock& current = values[target].sources[index];
                    SourceBlock& next = values[target + 1].sources[index];
                    if( current.error > next.error + 1 )
                    {
                        current.start = next.start;
                        current.end = next.end;
                        current.error = next.error + 1;
                        stable = false;
                    }
                }
                if( target != 0 )
                {
                    SourceBlock& current = values[target].sources[index];
                    SourceBlock& previous = values[target - 1].sources[index];
                    if( current.error > previous.error + 1 )
                    {
                        current.start = previous.start;
                        current.end = previous.end;
                        current.error = previous.error + 1;
                        stable = false;
                    }
                }
            }
        }
        if( stable )
            break;
    }

    // debug
    std::cout << "\nstatic SingleColourLookup const " << name << "[] = \n{\n";
    for( int i = 0;; )
    {
        std::cout << "\t{ { ";
        for( int j = 0;; )
        {
            SourceBlock const& block = values[i].sources[j];
            if( j < colours )
                std::cout << "{ " << block.start << ", " << block.end << ", " << block.error << " }";
            else
                std::cout << "{ 0, 0, 0 }";
            if( ++j == 2 )
                break;
            std::cout << ", ";
        }
        std::cout << " } }";
        if( ++i == 256 )
            break;
        std::cout << ",\n";
    }
    std::cout << "\n};\n";
}

int main()
{
    GenerateData( "lookup_5_3", 5, 3 );
    GenerateData( "lookup_6_3", 6, 3 );
    GenerateData( "lookup_5_4", 5, 4 );
    GenerateData( "lookup_6_4", 6, 4 );
}