mapnik/include/mapnik/jpeg_io.hpp

/*****************************************************************************
 * 
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2006 Artem Pavlenko
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/

//$Id$

extern "C"
{
#include <jpeglib.h>
}

namespace mapnik {

#define BUFFER_SIZE 4096
   
   typedef struct  
   {
         struct jpeg_destination_mgr pub;
         std::ostream * out;
         JOCTET * buffer;
   } dest_mgr;
   
   inline void init_destination( j_compress_ptr cinfo)
   {
      dest_mgr * dest = reinterpret_cast<dest_mgr*>(cinfo->dest);
      dest->buffer = (JOCTET*) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                                           BUFFER_SIZE * sizeof(JOCTET));
      dest->pub.next_output_byte = dest->buffer;
      dest->pub.free_in_buffer = BUFFER_SIZE;
   }

   inline boolean empty_output_buffer (j_compress_ptr cinfo)
   {
      dest_mgr * dest = reinterpret_cast<dest_mgr*>(cinfo->dest);
      dest->out->write((char*)dest->buffer, BUFFER_SIZE);
      if (!*(dest->out)) return false;
      dest->pub.next_output_byte = dest->buffer;
      dest->pub.free_in_buffer = BUFFER_SIZE;
      return true;
   }
   
   inline void term_destination( j_compress_ptr cinfo)
   {
      dest_mgr * dest = reinterpret_cast<dest_mgr*>(cinfo->dest);
      size_t size  = BUFFER_SIZE - dest->pub.free_in_buffer;
      if (size > 0) 
      {
         dest->out->write((char*)dest->buffer, size);
      }
      dest->out->flush();
   }
   
   template <typename T1, typename T2>
   void save_as_jpeg(T1 & file,int quality, T2 const& image)
   {  
      struct jpeg_compress_struct cinfo;
      struct jpeg_error_mgr jerr;

      int width=image.width();
      int height=image.height();
	
      cinfo.err = jpeg_std_error(&jerr);
      jpeg_create_compress(&cinfo);
    
      cinfo.dest = (struct jpeg_destination_mgr *)(*cinfo.mem->alloc_small)
         ((j_common_ptr) &cinfo, JPOOL_PERMANENT, sizeof(dest_mgr));
      dest_mgr * dest = (dest_mgr*) cinfo.dest;
      dest->pub.init_destination = init_destination;
      dest->pub.empty_output_buffer = empty_output_buffer;
      dest->pub.term_destination = term_destination;
      dest->out = &file;
      
      //jpeg_stdio_dest(&cinfo, fp);
      cinfo.image_width = width;
      cinfo.image_height = height;
      cinfo.input_components = 3;
      cinfo.in_color_space = JCS_RGB; 
      jpeg_set_defaults(&cinfo);
      jpeg_set_quality(&cinfo, quality,1);
      jpeg_start_compress(&cinfo, 1);
      JSAMPROW row_pointer[1];
      JSAMPLE* row=reinterpret_cast<JSAMPLE*>( ::operator new (sizeof(JSAMPLE) * width*3));
      while (cinfo.next_scanline < cinfo.image_height) 
      {
         const unsigned* imageRow=image.getRow(cinfo.next_scanline);
         int index=0;
         for (int i=0;i<width;++i)
         {
            row[index++]=(imageRow[i])&0xff;
            row[index++]=(imageRow[i]>>8)&0xff;
            row[index++]=(imageRow[i]>>16)&0xff;
         }
         row_pointer[0] = &row[0];
         (void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
      }
      ::operator delete(row);
      
      jpeg_finish_compress(&cinfo);
      jpeg_destroy_compress(&cinfo);
   }  
}