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/* -----------------------------------------------------------------------------
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 "colourblock.h"
namespace squish {
static int FloatToInt( float a, int limit )
{
// use ANSI round-to-zero behaviour to get round-to-nearest
int i = ( int )( a + 0.5f );
// clamp to the limit
if( i < 0 )
i = 0;
else if( i > limit )
i = limit;
// done
return i;
}
static int FloatTo565( Vec3::Arg colour )
{
// get the components in the correct range
int r = FloatToInt( 31.0f*colour.X(), 31 );
int g = FloatToInt( 63.0f*colour.Y(), 63 );
int b = FloatToInt( 31.0f*colour.Z(), 31 );
// pack into a single value
return ( r << 11 ) | ( g << 5 ) | b;
}
static void WriteColourBlock( int a, int b, u8* indices, void* block )
{
// get the block as bytes
u8* bytes = ( u8* )block;
// write the endpoints
bytes[0] = ( u8 )( a & 0xff );
bytes[1] = ( u8 )( a >> 8 );
bytes[2] = ( u8 )( b & 0xff );
bytes[3] = ( u8 )( b >> 8 );
// write the indices
for( int i = 0; i < 4; ++i )
{
u8 const* ind = indices + 4*i;
bytes[4 + i] = ind[0] | ( ind[1] << 2 ) | ( ind[2] << 4 ) | ( ind[3] << 6 );
}
}
void WriteColourBlock3( Vec3::Arg start, Vec3::Arg end, u8 const* indices, void* block )
{
// get the packed values
int a = FloatTo565( start );
int b = FloatTo565( end );
// remap the indices
u8 remapped[16];
if( a <= b )
{
// use the indices directly
for( int i = 0; i < 16; ++i )
remapped[i] = indices[i];
}
else
{
// swap a and b
std::swap( a, b );
for( int i = 0; i < 16; ++i )
{
if( indices[i] == 0 )
remapped[i] = 1;
else if( indices[i] == 1 )
remapped[i] = 0;
else
remapped[i] = indices[i];
}
}
// write the block
WriteColourBlock( a, b, remapped, block );
}
void WriteColourBlock4( Vec3::Arg start, Vec3::Arg end, u8 const* indices, void* block )
{
// get the packed values
int a = FloatTo565( start );
int b = FloatTo565( end );
// remap the indices
u8 remapped[16];
if( a < b )
{
// swap a and b
std::swap( a, b );
for( int i = 0; i < 16; ++i )
remapped[i] = ( indices[i] ^ 0x1 ) & 0x3;
}
else if( a == b )
{
// use index 0
for( int i = 0; i < 16; ++i )
remapped[i] = 0;
}
else
{
// use the indices directly
for( int i = 0; i < 16; ++i )
remapped[i] = indices[i];
}
// write the block
WriteColourBlock( a, b, remapped, block );
}
static int Unpack565( u8 const* packed, u8* colour )
{
// build the packed value
int value = ( int )packed[0] | ( ( int )packed[1] << 8 );
// get the components in the stored range
u8 red = ( u8 )( ( value >> 11 ) & 0x1f );
u8 green = ( u8 )( ( value >> 5 ) & 0x3f );
u8 blue = ( u8 )( value & 0x1f );
// scale up to 8 bits
colour[0] = ( red << 3 ) | ( red >> 2 );
colour[1] = ( green << 2 ) | ( green >> 4 );
colour[2] = ( blue << 3 ) | ( blue >> 2 );
colour[3] = 255;
// return the value
return value;
}
void DecompressColour( u8* rgba, void const* block, bool isDxt1 )
{
// get the block bytes
u8 const* bytes = reinterpret_cast< u8 const* >( block );
// unpack the endpoints
u8 codes[16];
int a = Unpack565( bytes, codes );
int b = Unpack565( bytes + 2, codes + 4 );
// generate the midpoints
for( int i = 0; i < 3; ++i )
{
int c = codes[i];
int d = codes[4 + i];
if( isDxt1 && a <= b )
{
codes[8 + i] = ( u8 )( ( c + d )/2 );
codes[12 + i] = 0;
}
else
{
codes[8 + i] = ( u8 )( ( 2*c + d )/3 );
codes[12 + i] = ( u8 )( ( c + 2*d )/3 );
}
}
// fill in alpha for the intermediate values
codes[8 + 3] = 255;
codes[12 + 3] = ( isDxt1 && a <= b ) ? 0 : 255;
// unpack the indices
u8 indices[16];
for( int i = 0; i < 4; ++i )
{
u8* ind = indices + 4*i;
u8 packed = bytes[4 + i];
ind[0] = packed & 0x3;
ind[1] = ( packed >> 2 ) & 0x3;
ind[2] = ( packed >> 4 ) & 0x3;
ind[3] = ( packed >> 6 ) & 0x3;
}
// store out the colours
for( int i = 0; i < 16; ++i )
{
u8 offset = 4*indices[i];
for( int j = 0; j < 4; ++j )
rgba[4*i + j] = codes[offset + j];
}
}
} // namespace squish
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