mapnik/src/png_reader.cpp

/*****************************************************************************
 * 
 * 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: png_reader.cpp 33 2005-04-04 13:01:03Z pavlenko $

#include <iostream>
#include <mapnik/image_reader.hpp>

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

namespace mapnik
{
    class PngReader : public ImageReader 
    {
    private:
        std::string fileName_;
        unsigned width_;
        unsigned height_;
        int bit_depth_;
        int color_type_;
    public:
        explicit PngReader(const std::string& fileName);
        ~PngReader();
        unsigned width() const;
        unsigned height() const;
        void read(unsigned x,unsigned y,ImageData32& image);	
    private:
        PngReader(const PngReader&);	
        PngReader& operator=(const PngReader&);
        void init();
    };

    namespace 
    {
        ImageReader* createPngReader(const std::string& file)
        {
            return new PngReader(file);
        }
        const bool registered = register_image_reader("png",createPngReader);
    }

    PngReader::PngReader(const std::string& fileName) 
        : fileName_(fileName),
          width_(0),
          height_(0),
          bit_depth_(0),
          color_type_(0)
    {
        init();
    }

    PngReader::~PngReader() {}

    static void
    png_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
    {
        png_size_t check;
        check = (png_size_t)fread(data, (png_size_t)1, length,
                                  (FILE *)png_ptr->io_ptr);

        if (check != length)
        {
            png_error(png_ptr, "Read Error");
        }
    }
  

    void PngReader::init()
    {
        FILE *fp=fopen(fileName_.c_str(),"rb");
        if (!fp) throw ImageReaderException("cannot open image file "+fileName_);
        png_byte header[8];
        memset(header,0,8);
        fread(header,1,8,fp);
        int is_png=!png_sig_cmp(header,0,8);
        if (!is_png)
        {
            fclose(fp);
            throw ImageReaderException(fileName_ + " is not a png file");
        }
        png_structp png_ptr = png_create_read_struct
            (PNG_LIBPNG_VER_STRING,0,0,0);

        if (!png_ptr) 
        {
            fclose(fp);
            throw ImageReaderException("failed to allocate png_ptr");
        }
        png_infop info_ptr = png_create_info_struct(png_ptr);
        if (!info_ptr)
        {
            png_destroy_read_struct(&png_ptr,0,0);
            fclose(fp);
            throw ImageReaderException("failed to create info_ptr");
        }

        png_set_read_fn(png_ptr, (png_voidp)fp, png_read_data);

        png_set_sig_bytes(png_ptr,8);
        png_read_info(png_ptr, info_ptr);

        png_uint_32  width, height;
        png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth_, &color_type_,0,0,0);

        width_=width;
        height_=height;
#ifdef MAPNIK_DEBUG
        std::clog<<"bit_depth="<<bit_depth_<<" color_type="<<color_type_<<std::endl;
#endif
        png_destroy_read_struct(&png_ptr,&info_ptr,0);	
        fclose(fp);
    }

    unsigned PngReader::width() const 
    {
        return width_;
    }

    unsigned PngReader::height() const 
    {
        return height_;
    }
    
    void PngReader::read(unsigned x0, unsigned y0,ImageData32& image) 
    {
        FILE *fp=fopen(fileName_.c_str(),"rb");
        if (!fp) throw ImageReaderException("cannot open image file "+fileName_);

        png_structp png_ptr = png_create_read_struct
            (PNG_LIBPNG_VER_STRING,0,0,0);

        if (!png_ptr) 
        {
            fclose(fp);
            throw ImageReaderException("failed to allocate png_ptr");
        }

        png_infop info_ptr = png_create_info_struct(png_ptr);
        if (!info_ptr)
        {
            png_destroy_read_struct(&png_ptr,0,0);
            fclose(fp);
            throw ImageReaderException("failed to create info_ptr");
        }

        png_set_read_fn(png_ptr, (png_voidp)fp, png_read_data);
        png_read_info(png_ptr, info_ptr);

        if (color_type_ == PNG_COLOR_TYPE_PALETTE)
            png_set_expand(png_ptr);
        if (color_type_ == PNG_COLOR_TYPE_GRAY && bit_depth_ < 8)
            png_set_expand(png_ptr);
        if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
            png_set_expand(png_ptr);
        if (bit_depth_ == 16)
            png_set_strip_16(png_ptr);
        if (color_type_ == PNG_COLOR_TYPE_GRAY ||
            color_type_ == PNG_COLOR_TYPE_GRAY_ALPHA)
            png_set_gray_to_rgb(png_ptr);

        // quick hack -- only work in >=libpng 1.2.7
        png_set_add_alpha(png_ptr,0xff,PNG_FILLER_AFTER); //rgba
        
        double gamma;
        if (png_get_gAMA(png_ptr, info_ptr, &gamma))
            png_set_gamma(png_ptr, 2.2, gamma);

        png_read_update_info(png_ptr, info_ptr);

        //START read image rows
        unsigned w=std::min((unsigned)image.width(),width_);
        unsigned h=std::min((unsigned)image.height(),height_);

        unsigned rowbytes=png_get_rowbytes(png_ptr, info_ptr);
        unsigned char* row= new unsigned char[rowbytes];
        for (unsigned i=0;i<height_;++i)
        {
            png_read_row(png_ptr,row,0);
            if (i>=y0 && i<h) 
            {
                image.setRow(i-y0,(unsigned*) &row[x0],w);
            } 
        }
        //END
        delete [] row;
        png_read_end(png_ptr,0);
        png_destroy_read_struct(&png_ptr, &info_ptr,0);
        fclose(fp);
    }
}