PNGCompressor.h

/*  IIP PNG Compressor Class:
    Handles alpha channels, 8 or 16 bit data, ICC profiles and XMP metadata
 
    Copyright (C) 2012-2024 Ruven Pillay
 
    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 3 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
 
*/
 
 
#ifndef _PNGCOMPRESSOR_H
#define _PNGCOMPRESSOR_H
 
 
#include "Compressor.h"
#include <png.h>
 
 
// Define ourselves a set of fast filters if necessary
#ifndef PNG_FAST_FILTERS // libpng < 1.6
#define PNG_FAST_FILTERS ( PNG_FILTER_NONE | PNG_FILTER_SUB | PNG_FILTER_UP )
#endif
 
 
 
typedef struct {
 
  png_structp png_ptr;               
  png_infop info_ptr;                
 
  unsigned char* output;             
  size_t output_size;                
  size_t written;                    
  unsigned int strip_height;         
  unsigned int bytes_per_pixel;      
 
} png_destination_mgr;
 
typedef png_destination_mgr *png_destination_ptr;
 
 
 
class PNGCompressor : public Compressor {
 
 private:
 
  unsigned int width;         
  unsigned int height;        
  png_uint_32 channels;       
 
  png_destination_mgr dest;   
 
  // The Compressor class Q parameter stores the zlib compression level (0-9)
  int filterType;             
  
  void writeMetadata();
 
  void writeResolution();
 
  void writeICCProfile();
 
  void writeXMPMetadata();
 
  void writeExifMetadata();
 
 
 public:
 
 
  PNGCompressor( int compressionLevel ) : Compressor(compressionLevel) {
 
    dest.png_ptr = NULL;
    dest.info_ptr = NULL;
 
    // Buffer for the data written by PNG library
    dest.output_size = 0;
 
    width = 0;
    height = 0;
    channels = 0;
 
    // Filters are an optional pre-processing step before Deflate compression
    //  - set this to the fastest set of filters
    filterType = PNG_FAST_FILTERS;
 
  };
 
 
 
  void InitCompression( const RawTile& rawtile, unsigned int strip_height );
 
 
 
  unsigned int CompressStrip( unsigned char* source, unsigned char* output, unsigned int tile_height );
 
 
 
  unsigned int Finish( unsigned char* output );
 
 
 
  unsigned int Compress( RawTile& t );
 
 
  inline const char* getMimeType() const { return "image/png"; }
 
  inline const char* getSuffix() const { return "png"; }
 
  inline ImageEncoding getImageEncoding() const { return ImageEncoding::PNG; };
 
 
 
  inline void setQuality( int quality ){
 
    // Flag that user has manually changed quality level
    default_quality = false;
 
    // Deflate compression level
    if( quality < 0 ) Q = 0;
    else if( quality > 9 ) Q = 9;
    else Q = quality;
  }
 
 
};
 
#endif