jpgencoderquantization.cpp

Jpeg编解码器的源代码

//
// Copyright (c) 1997,1998 Colosseum Builders, Inc.
// All rights reserved.
//
// Colosseum Builders, Inc. makes no warranty, expressed or implied
// with regards to this software. It is provided as is.
//
// See the README.TXT file that came with this software for restrictions
// on the use and redistribution of this file or send E-mail to
// [e-mail]
//

//
// JPEG Encoder Library.
//
// Title:   EncoderQuantizationTable Class Implementation
//
// Author: John M. Miano  [e-mail]
//
//

#include "jpgencoderquantization.h"
#include "jpgencoder.h"

using namespace Colosseum ;
namespace ColosseumPrivate
{

//
// This table consists of the values
//
//   F (i, j) = X (i) X (j) / 8
//
// where
//
//  X (n) = 1, n = 0, 4
//  X (n) = 1 / sqrt(2) / cos (n*PI/16)
//

const double floatscaling [JPEGSAMPLESIZE] =
{
 0.125,                  0.09011997775086849627, 0.09567085809127244544, 0.1063037618459070632,  0.125,                  0.159094822571604233,  0.2309698831278216846, 0.4530637231764438333, 
 0.09011997775086849627, 0.0649728831185362593,  0.0689748448207357645,  0.07664074121909414394, 0.09011997775086849627, 0.1147009749634507608, 0.1665200058287998886, 0.3266407412190940884, 
 0.09567085809127244544, 0.0689748448207357645,  0.0732233047033631207,  0.08136137691302557096, 0.09567085809127244544, 0.1217659055464329343, 0.1767766952966368932, 0.3467599613305368256, 
 0.1063037618459070632,  0.07664074121909414394, 0.08136137691302557096, 0.09040391826073060355, 0.1063037618459070632,  0.135299025036549253,  0.1964237395967755595, 0.3852990250365491698, 
 0.125,                  0.09011997775086849627, 0.09567085809127244544, 0.1063037618459070632,  0.125,                  0.159094822571604233,  0.2309698831278216846, 0.4530637231764438333, 
 0.159094822571604233,   0.1147009749634507608,  0.1217659055464329343,  0.135299025036549253,   0.159094822571604233,   0.2024893005527218515, 0.2939689006048396558, 0.5766407412190940329, 
 0.2309698831278216846,  0.1665200058287998886,  0.1767766952966368932,  0.1964237395967755595,  0.2309698831278216846,  0.2939689006048396558, 0.4267766952966368654, 0.8371526015321518744, 
 0.4530637231764438333,  0.3266407412190940884,  0.3467599613305368256,  0.3852990250365491698,  0.4530637231764438333,  0.5766407412190940329, 0.8371526015321518744, 1.642133898068010689,  
} ;

//
//  Description:
//
//    Default Class Constructor
//

JpegEncoderQuantizationTable::JpegEncoderQuantizationTable ()
{
  memset (data_values, 0, sizeof (data_values)) ;
  return ;
}

//
//  Description:
//
//    This function creates the scaled quantization tables used by the fast
//    FDCT algorithm.
//
void JpegEncoderQuantizationTable::buildScaledTables ()
{
  for (unsigned int ii = 0 ; ii < JPEGSAMPLESIZE ; ++ ii)
  {
    float_scaling [ii] = floatscaling [ii] / data_values [ii] ;
  }
  return ;
}


} // End Namespace ColosseumPrivate