350 lines
9.3 KiB
C++
350 lines
9.3 KiB
C++
/* -----------------------------------------------------------------------------
|
|
|
|
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 "alpha.h"
|
|
|
|
#include <climits>
|
|
#include <algorithm>
|
|
|
|
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;
|
|
}
|
|
|
|
void CompressAlphaDxt3( u8 const* rgba, int mask, void* block )
|
|
{
|
|
u8* bytes = reinterpret_cast< u8* >( block );
|
|
|
|
// quantise and pack the alpha values pairwise
|
|
for( int i = 0; i < 8; ++i )
|
|
{
|
|
// quantise down to 4 bits
|
|
float alpha1 = ( float )rgba[8*i + 3] * ( 15.0f/255.0f );
|
|
float alpha2 = ( float )rgba[8*i + 7] * ( 15.0f/255.0f );
|
|
int quant1 = FloatToInt( alpha1, 15 );
|
|
int quant2 = FloatToInt( alpha2, 15 );
|
|
|
|
// set alpha to zero where masked
|
|
int bit1 = 1 << ( 2*i );
|
|
int bit2 = 1 << ( 2*i + 1 );
|
|
if( ( mask & bit1 ) == 0 )
|
|
quant1 = 0;
|
|
if( ( mask & bit2 ) == 0 )
|
|
quant2 = 0;
|
|
|
|
// pack into the byte
|
|
bytes[i] = ( u8 )( quant1 | ( quant2 << 4 ) );
|
|
}
|
|
}
|
|
|
|
void DecompressAlphaDxt3( u8* rgba, void const* block )
|
|
{
|
|
u8 const* bytes = reinterpret_cast< u8 const* >( block );
|
|
|
|
// unpack the alpha values pairwise
|
|
for( int i = 0; i < 8; ++i )
|
|
{
|
|
// quantise down to 4 bits
|
|
u8 quant = bytes[i];
|
|
|
|
// unpack the values
|
|
u8 lo = quant & 0x0f;
|
|
u8 hi = quant & 0xf0;
|
|
|
|
// convert back up to bytes
|
|
rgba[8*i + 3] = lo | ( lo << 4 );
|
|
rgba[8*i + 7] = hi | ( hi >> 4 );
|
|
}
|
|
}
|
|
|
|
static void FixRange( int& min, int& max, int steps )
|
|
{
|
|
if( max - min < steps )
|
|
max = std::min( min + steps, 255 );
|
|
if( max - min < steps )
|
|
min = std::max( 0, max - steps );
|
|
}
|
|
|
|
static int FitCodes( u8 const* rgba, int mask, u8 const* codes, u8* indices )
|
|
{
|
|
// fit each alpha value to the codebook
|
|
int err = 0;
|
|
for( int i = 0; i < 16; ++i )
|
|
{
|
|
// check this pixel is valid
|
|
int bit = 1 << i;
|
|
if( ( mask & bit ) == 0 )
|
|
{
|
|
// use the first code
|
|
indices[i] = 0;
|
|
continue;
|
|
}
|
|
|
|
// find the least error and corresponding index
|
|
int value = rgba[4*i + 3];
|
|
int least = INT_MAX;
|
|
int index = 0;
|
|
for( int j = 0; j < 8; ++j )
|
|
{
|
|
// get the squared error from this code
|
|
int dist = ( int )value - ( int )codes[j];
|
|
dist *= dist;
|
|
|
|
// compare with the best so far
|
|
if( dist < least )
|
|
{
|
|
least = dist;
|
|
index = j;
|
|
}
|
|
}
|
|
|
|
// save this index and accumulate the error
|
|
indices[i] = ( u8 )index;
|
|
err += least;
|
|
}
|
|
|
|
// return the total error
|
|
return err;
|
|
}
|
|
|
|
static void WriteAlphaBlock( int alpha0, int alpha1, u8 const* indices, void* block )
|
|
{
|
|
u8* bytes = reinterpret_cast< u8* >( block );
|
|
|
|
// write the first two bytes
|
|
bytes[0] = ( u8 )alpha0;
|
|
bytes[1] = ( u8 )alpha1;
|
|
|
|
// pack the indices with 3 bits each
|
|
u8* dest = bytes + 2;
|
|
u8 const* src = indices;
|
|
for( int i = 0; i < 2; ++i )
|
|
{
|
|
// pack 8 3-bit values
|
|
int value = 0;
|
|
for( int j = 0; j < 8; ++j )
|
|
{
|
|
int index = *src++;
|
|
value |= ( index << 3*j );
|
|
}
|
|
|
|
// store in 3 bytes
|
|
for( int j = 0; j < 3; ++j )
|
|
{
|
|
int byte = ( value >> 8*j ) & 0xff;
|
|
*dest++ = ( u8 )byte;
|
|
}
|
|
}
|
|
}
|
|
|
|
static void WriteAlphaBlock5( int alpha0, int alpha1, u8 const* indices, void* block )
|
|
{
|
|
// check the relative values of the endpoints
|
|
if( alpha0 > alpha1 )
|
|
{
|
|
// swap the indices
|
|
u8 swapped[16];
|
|
for( int i = 0; i < 16; ++i )
|
|
{
|
|
u8 index = indices[i];
|
|
if( index == 0 )
|
|
swapped[i] = 1;
|
|
else if( index == 1 )
|
|
swapped[i] = 0;
|
|
else if( index <= 5 )
|
|
swapped[i] = 7 - index;
|
|
else
|
|
swapped[i] = index;
|
|
}
|
|
|
|
// write the block
|
|
WriteAlphaBlock( alpha1, alpha0, swapped, block );
|
|
}
|
|
else
|
|
{
|
|
// write the block
|
|
WriteAlphaBlock( alpha0, alpha1, indices, block );
|
|
}
|
|
}
|
|
|
|
static void WriteAlphaBlock7( int alpha0, int alpha1, u8 const* indices, void* block )
|
|
{
|
|
// check the relative values of the endpoints
|
|
if( alpha0 < alpha1 )
|
|
{
|
|
// swap the indices
|
|
u8 swapped[16];
|
|
for( int i = 0; i < 16; ++i )
|
|
{
|
|
u8 index = indices[i];
|
|
if( index == 0 )
|
|
swapped[i] = 1;
|
|
else if( index == 1 )
|
|
swapped[i] = 0;
|
|
else
|
|
swapped[i] = 9 - index;
|
|
}
|
|
|
|
// write the block
|
|
WriteAlphaBlock( alpha1, alpha0, swapped, block );
|
|
}
|
|
else
|
|
{
|
|
// write the block
|
|
WriteAlphaBlock( alpha0, alpha1, indices, block );
|
|
}
|
|
}
|
|
|
|
void CompressAlphaDxt5( u8 const* rgba, int mask, void* block )
|
|
{
|
|
// get the range for 5-alpha and 7-alpha interpolation
|
|
int min5 = 255;
|
|
int max5 = 0;
|
|
int min7 = 255;
|
|
int max7 = 0;
|
|
for( int i = 0; i < 16; ++i )
|
|
{
|
|
// check this pixel is valid
|
|
int bit = 1 << i;
|
|
if( ( mask & bit ) == 0 )
|
|
continue;
|
|
|
|
// incorporate into the min/max
|
|
int value = rgba[4*i + 3];
|
|
if( value < min7 )
|
|
min7 = value;
|
|
if( value > max7 )
|
|
max7 = value;
|
|
if( value != 0 && value < min5 )
|
|
min5 = value;
|
|
if( value != 255 && value > max5 )
|
|
max5 = value;
|
|
}
|
|
|
|
// handle the case that no valid range was found
|
|
if( min5 > max5 )
|
|
min5 = max5;
|
|
if( min7 > max7 )
|
|
min7 = max7;
|
|
|
|
// fix the range to be the minimum in each case
|
|
FixRange( min5, max5, 5 );
|
|
FixRange( min7, max7, 7 );
|
|
|
|
// set up the 5-alpha code book
|
|
u8 codes5[8];
|
|
codes5[0] = ( u8 )min5;
|
|
codes5[1] = ( u8 )max5;
|
|
for( int i = 1; i < 5; ++i )
|
|
codes5[1 + i] = ( u8 )( ( ( 5 - i )*min5 + i*max5 )/5 );
|
|
codes5[6] = 0;
|
|
codes5[7] = 255;
|
|
|
|
// set up the 7-alpha code book
|
|
u8 codes7[8];
|
|
codes7[0] = ( u8 )min7;
|
|
codes7[1] = ( u8 )max7;
|
|
for( int i = 1; i < 7; ++i )
|
|
codes7[1 + i] = ( u8 )( ( ( 7 - i )*min7 + i*max7 )/7 );
|
|
|
|
// fit the data to both code books
|
|
u8 indices5[16];
|
|
u8 indices7[16];
|
|
int err5 = FitCodes( rgba, mask, codes5, indices5 );
|
|
int err7 = FitCodes( rgba, mask, codes7, indices7 );
|
|
|
|
// save the block with least error
|
|
if( err5 <= err7 )
|
|
WriteAlphaBlock5( min5, max5, indices5, block );
|
|
else
|
|
WriteAlphaBlock7( min7, max7, indices7, block );
|
|
}
|
|
|
|
void DecompressAlphaDxt5( u8* rgba, void const* block )
|
|
{
|
|
// get the two alpha values
|
|
u8 const* bytes = reinterpret_cast< u8 const* >( block );
|
|
int alpha0 = bytes[0];
|
|
int alpha1 = bytes[1];
|
|
|
|
// compare the values to build the codebook
|
|
u8 codes[8];
|
|
codes[0] = ( u8 )alpha0;
|
|
codes[1] = ( u8 )alpha1;
|
|
if( alpha0 <= alpha1 )
|
|
{
|
|
// use 5-alpha codebook
|
|
for( int i = 1; i < 5; ++i )
|
|
codes[1 + i] = ( u8 )( ( ( 5 - i )*alpha0 + i*alpha1 )/5 );
|
|
codes[6] = 0;
|
|
codes[7] = 255;
|
|
}
|
|
else
|
|
{
|
|
// use 7-alpha codebook
|
|
for( int i = 1; i < 7; ++i )
|
|
codes[1 + i] = ( u8 )( ( ( 7 - i )*alpha0 + i*alpha1 )/7 );
|
|
}
|
|
|
|
// decode the indices
|
|
u8 indices[16];
|
|
u8 const* src = bytes + 2;
|
|
u8* dest = indices;
|
|
for( int i = 0; i < 2; ++i )
|
|
{
|
|
// grab 3 bytes
|
|
int value = 0;
|
|
for( int j = 0; j < 3; ++j )
|
|
{
|
|
int byte = *src++;
|
|
value |= ( byte << 8*j );
|
|
}
|
|
|
|
// unpack 8 3-bit values from it
|
|
for( int j = 0; j < 8; ++j )
|
|
{
|
|
int index = ( value >> 3*j ) & 0x7;
|
|
*dest++ = ( u8 )index;
|
|
}
|
|
}
|
|
|
|
// write out the indexed codebook values
|
|
for( int i = 0; i < 16; ++i )
|
|
rgba[4*i + 3] = codes[indices[i]];
|
|
}
|
|
|
|
} // namespace squish
|