info.hpp

Go to the documentation of this file.

/*
 * Copyright (C) 2007,2008   Alex Shulgin
 *
 * This file is part of png++ the C++ wrapper for libpng.  PNG++ is free
 * software; the exact copying conditions are as follows:
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * 3. The name of the author may not be used to endorse or promote products
 * derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
 * NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#ifndef PNGPP_INFO_HPP_INCLUDED
#define PNGPP_INFO_HPP_INCLUDED

#include <cassert>
#include "info_base.hpp"
#include "image_info.hpp"

namespace png
{

    class info
        : public info_base,
          public image_info
    {
    public:
        info(io_base& io, png_struct* png)
            : info_base(io, png)
        {
        }

        void read()
        {
            assert(m_png);
            assert(m_info);

            png_read_info(m_png, m_info);
            png_get_IHDR(m_png,
                         m_info,
                         & m_width,
                         & m_height,
                         reinterpret_cast< int* >(& m_bit_depth),
                         reinterpret_cast< int* >(& m_color_type),
                         reinterpret_cast< int* >(& m_interlace_type),
                         reinterpret_cast< int* >(& m_compression_type),
                         reinterpret_cast< int* >(& m_filter_type));

            if (png_get_valid(m_png, m_info, chunk_PLTE) == chunk_PLTE)
            {
                png_color* colors = 0;
                int count = 0;
                png_get_PLTE(m_png, m_info, & colors, & count);
                m_palette.assign(colors, colors + count);
            }
#ifdef PNG_tRNS_SUPPORTED
            if (png_get_valid(m_png, m_info, chunk_tRNS) == chunk_tRNS)
            {
                if (m_color_type == color_type_palette)
                {
                    int count;
                    byte* values;
                    if (png_get_tRNS(m_png, m_info, & values, & count, NULL)
                        != PNG_INFO_tRNS)
                    {
                        throw error("png_get_tRNS() failed");
                    }
                    m_tRNS.assign(values, values + count);
                }
            }
#endif
        }

        void write() const
        {
            assert(m_png);
            assert(m_info);

            sync_ihdr();
            if (m_color_type == color_type_palette)
            {
                if (! m_palette.empty())
                {
                    png_set_PLTE(m_png, m_info,
                                 const_cast< color* >(& m_palette[0]),
                                 m_palette.size());
                }
                if (! m_tRNS.empty())
                {
#ifdef PNG_tRNS_SUPPORTED
                    png_set_tRNS(m_png, m_info,
                                 const_cast< byte* >(& m_tRNS[0]),
                                 m_tRNS.size(),
                                 NULL);
#else
                    throw error("attempted to write tRNS chunk;"
                                " recompile with PNG_tRNS_SUPPORTED");
#endif
                }
            }
            png_write_info(m_png, m_info);
        }

        void update()
        {
            assert(m_png);
            assert(m_info);

            sync_ihdr();
            png_read_update_info(m_png, m_info);
        }

    protected:
        void sync_ihdr(void) const
        {
            png_set_IHDR(m_png,
                         m_info,
                         m_width,
                         m_height,
                         m_bit_depth,
                         m_color_type,
                         m_interlace_type,
                         m_compression_type,
                         m_filter_type);
        }
    };

} // namespace png

#endif // PNGPP_INFO_HPP_INCLUDED