convert_color_space.hpp

/*
 * 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_CONVERT_COLOR_SPACE_HPP_INCLUDED
#define PNGPP_CONVERT_COLOR_SPACE_HPP_INCLUDED

#include "error.hpp"
#include "rgb_pixel.hpp"
#include "rgba_pixel.hpp"
#include "gray_pixel.hpp"
#include "ga_pixel.hpp"
#include "index_pixel.hpp"
#include "reader.hpp"
#include "writer.hpp"

namespace png
{

    namespace detail
    {

        /**
         * \brief IO transformation class template.  Converts %image %color
         * space.
         */
        template< typename pixel >
        struct convert_color_space_impl
        {
            typedef pixel_traits< pixel > traits;
            typedef typename traits::component_type component_type;
            typedef basic_alpha_pixel_traits< component_type > alpha_traits;

            template< class reader >
            void operator()(reader& io) const
            {
                handle_16(io);
                handle_alpha(io, alpha_traits::get_alpha_filler());
                handle_palette(io);
                handle_rgb(io);
                handle_gray(io);

                io.set_color_type(traits::get_color_type());
                io.set_bit_depth(traits::get_bit_depth());
            }

        protected:
            static void expand_8_to_16(png_struct*, png_row_info* row_info,
                                       byte* row)
            {
#ifdef DEBUG_EXPAND_8_16
                printf("row: width=%d, bytes=%d, channels=%d\n",
                       row_info->width, row_info->rowbytes, row_info->channels);
                printf("<= ");
                dump_row(row, row_info->rowbytes);
#endif
                for (uint_32 i = row_info->rowbytes; i-- > 0; )
                {
                    row[2*i + 1] = row[i];
                    row[2*i + 0] = 0;
                }
#ifdef DEBUG_EXPAND_8_16
                printf("=> ");
                dump_row(row, 2*row_info->rowbytes);
#endif
            }

#ifdef DEBUG_EXPAND_8_16
            static void dump_row(byte const* row, uint_32 width)
            {
                printf("{");
                for (uint_32 i = 0; i < width; ++i)
                {
                    printf(" %02x,", row[i]);
                }
                printf(" }\n");
            }
#endif

            template< class reader >
            static void handle_16(reader& io)
            {
                if (io.get_bit_depth() == 16 && traits::get_bit_depth() == 8)
                {
#ifdef PNG_READ_16_TO_8_SUPPORTED
                    io.set_strip_16();
#else
                    throw error("expected 8-bit data but found 16-bit; recompile with PNG_READ_16_TO_8_SUPPORTED");
#endif
                }
                if (io.get_bit_depth() != 16 && traits::get_bit_depth() == 16)
                {
#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
                    io.set_read_user_transform(expand_8_to_16);
                    io.set_user_transform_info(NULL, 16,
                                               traits::get_channels());
#else
                    throw error("expected 16-bit data but found 8-bit; recompile with PNG_READ_USER_TRANSFORM_SUPPORTED");
#endif
                }
            }

            template< class reader >
            static void handle_alpha(reader& io, uint_32 filler)
            {
                bool src_alpha = (io.get_color_type() & color_mask_alpha);
                bool src_tRNS = io.has_chunk(chunk_tRNS);
                bool dst_alpha = traits::get_color_type() & color_mask_alpha;
                if ((src_alpha || src_tRNS) && !dst_alpha)
                {
#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
                    io.set_strip_alpha();
#else
                    throw error("alpha channel unexpected; recompile with PNG_READ_STRIP_ALPHA_SUPPORTED");
#endif
                }
                if (!src_alpha && dst_alpha)
                {
#if defined(PNG_tRNS_SUPPORTED) && defined(PNG_READ_EXPAND_SUPPORTED)
                    if (src_tRNS)
                    {
                        io.set_tRNS_to_alpha();
                        return;
                    }
#endif
#if defined(PNG_READ_FILLER_SUPPORTED) && !defined(PNG_1_0_X)
                    io.set_add_alpha(filler, filler_after);
#else
                    throw error("expected alpha channel but none found; recompile with PNG_READ_FILLER_SUPPORTED and be sure to use libpng > 1.0.x");
#endif
                }
            }

            template< class reader >
            static void handle_palette(reader& io)
            {
                bool src_palette =
                    io.get_color_type() == color_type_palette;
                bool dst_palette =
                    traits::get_color_type() == color_type_palette;
                if (src_palette && !dst_palette)
                {
#ifdef PNG_READ_EXPAND_SUPPORTED
                    io.set_palette_to_rgb();
                    io.get_info().drop_palette();
#else
                    throw error("indexed colors unexpected; recompile with PNG_READ_EXPAND_SUPPORTED");
#endif
                }
                else if (!src_palette && dst_palette)
                {
                    throw error("conversion to indexed colors is unsupported (yet)");
                }
                else if (src_palette && dst_palette
                         && io.get_bit_depth() != traits::get_bit_depth())
                {
                    if (traits::get_bit_depth() == 8)
                    {
#ifdef PNG_READ_PACK_SUPPORTED
                        io.set_packing();
#endif
                    }
                    else
                    {
                        throw error("cannot convert to indexed colors with bit-depth < 8");
                    }
                }
            }

            template< class reader >
            static void handle_rgb(reader& io)
            {
                bool src_rgb =
                    io.get_color_type() & (color_mask_rgb | color_mask_palette);
                bool dst_rgb = traits::get_color_type() & color_mask_rgb;
                if (src_rgb && !dst_rgb)
                {
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
                    io.set_rgb_to_gray(/*rgb_to_gray_error*/);
#else
                    throw error("grayscale data expected; recompile with PNG_READ_RGB_TO_GRAY_SUPPORTED");
#endif
                }
                if (!src_rgb && dst_rgb)
                {
#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
                    io.set_gray_to_rgb();
#else
                    throw error("expected RGB data; recompile with PNG_READ_GRAY_TO_RGB_SUPPORTED");
#endif
                }
            }

            template< class reader >
            static void handle_gray(reader& io)
            {
                if ((io.get_color_type() & ~color_mask_alpha)
                    == color_type_gray)
                {
                    if (io.get_bit_depth() < 8 && traits::get_bit_depth() >= 8)
                    {
#ifdef PNG_READ_EXPAND_SUPPORTED
                        io.set_gray_1_2_4_to_8();
#else
                        throw error("convert_color_space: expected 8-bit data; recompile with PNG_READ_EXPAND_SUPPORTED");
#endif
                    }
                }
            }
        };

    } // namespace detal

    /**
     * \brief IO transformation class template.  Converts %image %color
     * space.
     *
     * This IO transformation class template is used to convert %color
     * space of the source %image to the %color space of the target
     * %image.  An error with human-readable description is thrown
     * when the %color space could not be converted.  Often, this
     * means that you have to recompile libpng with some more
     * conversion options turned on.
     *
     * Not implemented--see specializations.
     *
     * \see image, image::read
     */
    template< typename pixel >
    struct convert_color_space
    {
    };

    /**
     * \brief Converts %image %color space.  A specialization for
     * rgb_pixel type.
     */
    template<>
    struct convert_color_space< rgb_pixel >
        : detail::convert_color_space_impl< rgb_pixel >
    {
    };

    /**
     * \brief Converts %image %color space.  A specialization for
     * rgb_pixel_16 type.
     */
    template<>
    struct convert_color_space< rgb_pixel_16 >
        : detail::convert_color_space_impl< rgb_pixel_16 >
    {
    };

    /**
     * \brief Converts %image %color space.  A specialization for
     * rgba_pixel type.
     */
    template<>
    struct convert_color_space< rgba_pixel >
        : detail::convert_color_space_impl< rgba_pixel >
    {
    };

    /**
     * \brief Converts %image %color space.  A specialization for
     * rgba_pixel_16 type.
     */
    template<>
    struct convert_color_space< rgba_pixel_16 >
        : detail::convert_color_space_impl< rgba_pixel_16 >
    {
    };

    /**
     * \brief Converts %image %color space.  A specialization for
     * gray_pixel type.
     */
    template<>
    struct convert_color_space< gray_pixel >
        : detail::convert_color_space_impl< gray_pixel >
    {
    };

    /**
     * \brief Converts %image %color space.  A specialization for
     * gray_pixel_16 type.
     */
    template<>
    struct convert_color_space< gray_pixel_16 >
        : detail::convert_color_space_impl< gray_pixel_16 >
    {
    };

    /**
     * \brief Converts %image %color space.  A specialization for
     * ga_pixel type.
     */
    template<>
    struct convert_color_space< ga_pixel >
        : detail::convert_color_space_impl< ga_pixel >
    {
    };

    /**
     * \brief Converts %image %color space.  A specialization for
     * ga_pixel_16 type.
     */
    template<>
    struct convert_color_space< ga_pixel_16 >
        : detail::convert_color_space_impl< ga_pixel_16 >
    {
    };

    /**
     * \brief Converts %image %color space.  A specialization for
     * index_pixel type.
     */
    template<>
    struct convert_color_space< index_pixel >
        : detail::convert_color_space_impl< index_pixel >
    {
    };

} // namespace png

#endif // PNGPP_CONVERT_COLOR_SPACE_HPP_INCLUDED