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# consumer.hpp

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    00001 /*
    00002  * Copyright (C) 2007,2008   Alex Shulgin
    00003  *
    00004  * This file is part of png++ the C++ wrapper for libpng.  PNG++ is free
    00005  * software; the exact copying conditions are as follows:
    00006  *
    00007  * Redistribution and use in source and binary forms, with or without
    00008  * modification, are permitted provided that the following conditions are met:
    00009  *
    00010  * 1. Redistributions of source code must retain the above copyright notice,
    00011  * this list of conditions and the following disclaimer.
    00012  *
    00013  * 2. Redistributions in binary form must reproduce the above copyright
    00014  * notice, this list of conditions and the following disclaimer in the
    00015  * documentation and/or other materials provided with the distribution.
    00016  *
    00017  * 3. The name of the author may not be used to endorse or promote products
    00018  * derived from this software without specific prior written permission.
    00019  *
    00020  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
    00021  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    00022  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
    00023  * NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    00024  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
    00025  * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
    00026  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
    00027  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
    00028  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
    00029  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    00030  */
    00031 #ifndef PNGPP_CONSUMER_HPP_INCLUDED
    00032 #define PNGPP_CONSUMER_HPP_INCLUDED
    00033
    00034 #include <cassert>
    00035 #include <stdexcept>
    00036 #include <iostream>
    00037 #include <istream>
    00038
    00039 #include "config.hpp"
    00040 #include "error.hpp"
    00041 #include "streaming_base.hpp"
    00042 #include "reader.hpp"
    00043 #include "pixel_buffer.hpp"
    00044
    00045 namespace png
    00046 {
    00047
    00121     template< typename pixel,
    00122               class pixcon,
    00123               class info_holder = def_image_info_holder,
    00124               bool interlacing_supported = false >
    00125     class consumer
    00126         : public streaming_base< pixel, info_holder >
    00127     {
    00128     public:
    00129         typedef pixel_traits< pixel > traits;
    00130
    00134         struct transform_identity
    00135         {
    00136             void operator()(io_base&) const {}
    00137         };
    00138
    00143         template< typename istream >
    00144         void read(istream& stream)
    00145         {
    00146             read(stream, transform_identity());
    00147         }
    00148
    00157         template< typename istream, class transformation >
    00158         void read(istream& stream, transformation const& transform)
    00159         {
    00160             reader< istream > rd(stream);
    00161             rd.read_info();
    00162             transform(rd);
    00163
    00164 #if __BYTE_ORDER == __LITTLE_ENDIAN
    00165             if (pixel_traits< pixel >::get_bit_depth() == 16)
    00166             {
    00167 #ifdef PNG_READ_SWAP_SUPPORTED
    00168                 rd.set_swap();
    00169 #else
    00170                 throw error("Cannot read 16-bit image:"
    00171                             " recompile with PNG_READ_SWAP_SUPPORTED.");
    00172 #endif
    00173             }
    00174 #endif
    00175
    00176             // interlace handling _must_ be set up prior to info update
    00177             size_t pass_count;
    00178             if (rd.get_interlace_type() != interlace_none)
    00179             {
    00180 #ifdef PNG_READ_INTERLACING_SUPPORTED
    00181                 pass_count = rd.set_interlace_handling();
    00182 #else
    00183                 throw error("Cannot read interlaced image:"
    00184                             " interlace handling disabled.");
    00185 #endif
    00186             }
    00187             else
    00188             {
    00189                 pass_count = 1;
    00190             }
    00191
    00192             rd.update_info();
    00193             if (rd.get_color_type() != traits::get_color_type()
    00194                 || rd.get_bit_depth() != traits::get_bit_depth())
    00195             {
    00196                 throw std::logic_error("color type and/or bit depth mismatch"
    00197                                        " in png::consumer::read()");
    00198             }
    00199
    00200             this->get_info() = rd.get_image_info();
    00201
    00202             pixcon* pixel_con = static_cast< pixcon* >(this);
    00203             if (pass_count > 1 && !interlacing_supported)
    00204             {
    00205                 skip_interlaced_rows(rd, pass_count);
    00206                 pass_count = 1;
    00207             }
    00208             read_rows(rd, pass_count, pixel_con);
    00209
    00210             rd.read_end_info();
    00211         }
    00212
    00213     protected:
    00214         typedef streaming_base< pixel, info_holder > base;
    00215
    00220         explicit consumer(image_info& info)
    00221             : base(info)
    00222         {
    00223         }
    00224
    00225     private:
    00226         template< typename istream >
    00227         void skip_interlaced_rows(reader< istream >& rd, size_t pass_count)
    00228         {
    00229             typedef std::vector< pixel > row;
    00230             typedef row_traits< row > row_traits_type;
    00231             row dummy_row(this->get_info().get_width());
    00232             for (size_t pass = 1; pass < pass_count; ++pass)
    00233             {
    00234                 rd.read_row(reinterpret_cast< byte* >
    00235                             (row_traits_type::get_data(dummy_row)));
    00236             }
    00237         }
    00238
    00239         template< typename istream >
    00240         void read_rows(reader< istream >& rd, size_t pass_count,
    00241                        pixcon* pixel_con)
    00242         {
    00243             for (size_t pass = 0; pass < pass_count; ++pass)
    00244             {
    00245                 pixel_con->reset(pass);
    00246
    00247                 for (size_t pos = 0; pos < this->get_info().get_height(); ++pos)
    00248                 {
    00249                     rd.read_row(pixel_con->get_next_row(pos));
    00250                 }
    00251             }
    00252         }
    00253     };
    00254
    00255 } // namespace png
    00256
    00257 #endif // PNGPP_CONSUMER_HPP_INCLUDED