downscale.cc

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/*--------------------------------------------------------------------
 *
 * (C) Copyright Koninklijke Philips Electronics NV 2006. 
 * All rights reserved. This software is licensed under the terms of
 * version 2.1 of the GNU Lesser General Public License as published 
 * by the Free Software Foundation. For licensing and warranty
 * information, see the file COPYING in the main directory.
 *
 *------------------------------------------------------------------*/

#include "downscale.h"

/* The number of bits coefficients are scaled up before 2-D IDCT: */
const unsigned int S_BITS = 3;

inline
VYApixel DESCALE(VYApixel x, unsigned int n) 
{
  return  (x + (1 << (n-1)) - (x < 0)) >> n;
}

DownScale::DownScale(
  const Id&     n, 
  In<VYApixel>&     cin, 
  Out<VYApixel>&    cout)
:
        Process(n),
        Cin(  id("Cin"),  cin),
        Cout( id("Cout"), cout)
{
}

void DownScale::main()
{
      VYApixel  pixelIn;
  VYApixel  pixelOut;

      while (true)
  {
    read(Cin, pixelIn);
  
                pixelOut = 128 + DESCALE(pixelIn, S_BITS+3);
                // Clip to 8 bits unsigned
    pixelOut = pixelOut > 0 ? (pixelOut < 255 ? pixelOut : 255) : 0;

    write(Cout, pixelOut);
  }
}

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