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ErrorDiffusionHalftoner.cxx

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/*
 * @(#)src/ErrorDiffusionHalftoner.cxx  1.0  2002-08-27 12:27
 *
 * Copyright (C)  2002  Daniel Léonard
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#include <algorithm>
#include <string>
#include "ErrorDiffusionHalftoner.h"
#include "ErrorDiffusionSpec.h"
#include "Image.h"

namespace halftoner
{

//------------------------------------------
// Class ErrorDiffusionHalftoner::PathStrategy
//------------------------------------------

//---------------------------
// Constructor
//---------------------------

   ErrorDiffusionHalftoner::PathStrategy::PathStrategy() throw()
   {
   // nothing
   }


//---------------------------
// Destructor
//---------------------------

   ErrorDiffusionHalftoner::PathStrategy::~PathStrategy() throw()
   {
   // nothing
   }


//------------------------------------------
// Class ErrorDiffusionHalftoner::ScanlinePathStrategy
//------------------------------------------

//---------------------------
// Overloaded operator
//---------------------------

   Image* ErrorDiffusionHalftoner::ScanlinePathStrategy::operator()(ErrorDiffusionHalftoner& halftoner, const Image& source, int threshold) throw()
   {
      Image* result = halftoner.scanline(source, threshold);
      return result;
   }


//------------------------------------------
// Class ErrorDiffusionHalftoner::SerpentinePathStrategy
//------------------------------------------

//---------------------------
// Overloaded operator
//---------------------------

   Image* ErrorDiffusionHalftoner::SerpentinePathStrategy::operator()(ErrorDiffusionHalftoner& halftoner, const Image& source, int threshold) throw()
   {
      Image* result = halftoner.serpentine(source, threshold);
      return result;
   }


//------------------------------------------
// Class ErrorDiffusionHalftoner
//------------------------------------------

//---------------------------
// Class variables
//---------------------------

   ErrorDiffusionHalftoner::ScanlinePathStrategy   ErrorDiffusionHalftoner::scan_line_strategy;
   ErrorDiffusionHalftoner::SerpentinePathStrategy ErrorDiffusionHalftoner::serpentine_strategy;

   ErrorDiffusionHalftoner::PathStrategy& ErrorDiffusionHalftoner::SCANLINE   = ErrorDiffusionHalftoner::scan_line_strategy;
   ErrorDiffusionHalftoner::PathStrategy& ErrorDiffusionHalftoner::SERPENTINE = ErrorDiffusionHalftoner::serpentine_strategy;


//---------------------------
// Constructor
//---------------------------

   ErrorDiffusionHalftoner::ErrorDiffusionHalftoner() throw()
   {
   // nothing
   }


//---------------------------
// Destructor
//---------------------------

   ErrorDiffusionHalftoner::~ErrorDiffusionHalftoner() throw()
   {
   // nothing
   }


//---------------------------
// Implemented methods from Halftoner
//---------------------------

   Image* ErrorDiffusionHalftoner::halftone(const Image& source, const HalftonerSpec* spec) throw (std::invalid_argument)
   {
   // check params
      if (0 == spec)
      {
         std::string message("HalftonerSpec* is 0");
         throw std::invalid_argument(message);
      }

   // cast the specs
      const ErrorDiffusionSpec* edspec = dynamic_cast<const ErrorDiffusionSpec*>(spec);
      if (0 == edspec)
      {
         std::string message("HalftonerSpec* is not an ErrorDiffusionSpec*");
         throw std::invalid_argument(message);
      }

   // extract the strategy
      ErrorDiffusionHalftoner::PathStrategy& strategy = edspec->getStrategy();

   // prepare variables for the strategy
      int threshold = edspec->getThreshold();
      ErrorDiffusionHalftoner& halftoner = *this;

   // call the strategy
      Image* result = strategy(halftoner, source, threshold);
      return result;
   }


//---------------------------
// Instance methods
//---------------------------

   Image* ErrorDiffusionHalftoner::scanline(const Image& source, int threshold)
   {
   // extract image data
      const int width = source.getWidth();
      const int height = source.getHeight();
      const int len = width * height;

   // create representation of the image with higher precision
      float data[len];

      unsigned char* copy = source.getCopy();
      std::copy_n(copy, len, data);
      delete copy;

   // create new image
      Image* destination = new Image(width, height);

   //   int line[width];
      int offset = 0;
      for (int j = 0; j < height; j++)
      {
   //      int* pixel = line;
         for (int i = 0; i < width; i++, offset++/*, pixel++*/)
         {
   //         *pixel = this->halftoneToRight(data, i, j, offset, width, height, threshold);
            int bw = this->halftoneToRight(data, i, j, offset, width, height, threshold);
            destination->setColorAt(i, j, bw);
         }
   //      destination->setLine(j, line, width);
      }

      return destination;
   }

   Image* ErrorDiffusionHalftoner::serpentine(const Image& source, int threshold)
   {
   // extract image data
      const int width = source.getWidth();
      const int height = source.getHeight();
      const int len = width * height;

   // create representation of the image with higher precision
      float data[len];

      unsigned char* copy = source.getCopy();
      std::copy_n(copy, len, data);
      delete copy;

   // create new image
      Image* destination = new Image(width, height);

      int line[width];
      for (int j = 0; j < height; j++)
      {
      // adjust pos at the beginning of the jth line.
         int pos = Image::calculateOffset(0, j, width);

         int* pixel = line;
         for (int i = 0; i < width; i++, pos++, pixel++)
         {
            *pixel = this->halftoneToRight(data, i, j, pos, width, height, threshold);
         }
         destination->setLine(j, line, width);

         j++;
         if (j >= height)
         {
            break;
         }

      // adjust pos at the end of the jth line.
         pos = Image::calculateOffset(0, j + 1, width);
         pos--;
      // adjust pixel at the end of the line
         pixel = line + width - 1;
         for (int i = width - 1; i >= 0; i--, pos--, pixel--)
         {
            *pixel = this->halftoneToLeft(data, i, j, pos, width, height, threshold);
         }
         destination->setLine(j, line, width);
      }

      return destination;
   }

}

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