    // Copyright (C) 2008  Davis E. King (davis@dlib.net), Nils Labugt
    // License: Boost Software License   See LICENSE.txt for the full license.
    #undef DLIB_PNG_IMPORT_ABSTRACT
    #ifdef DLIB_PNG_IMPORT_ABSTRACT

    #include "image_loader_abstract.h"
    #include "../algs.h"
    #include "../pixel.h"
    #include "../dir_nav.h"
    #include "../image_processing/generic_image.h"

    namespace dlib
    {

        class png_loader : noncopyable
        {
            /*!
                INITIAL VALUE
                    Defined by the constructors

                WHAT THIS OBJECT REPRESENTS
                    This object represents a class capable of loading PNG image files.
                    Once an instance of it is created to contain a PNG file from
                    disk you can obtain the image stored in it via get_image().
            !*/

        public:

            png_loader(
                const char* filename
            );
            /*!
                ensures
                    - loads the PNG file with the given file name into this object
                throws
                    - std::bad_alloc
                    - image_load_error
                      This exception is thrown if there is some error that prevents
                      us from loading the given PNG file.
            !*/

            png_loader(
                const std::string& filename
            );
            /*!
                ensures
                    - loads the PNG file with the given file name into this object
                throws
                    - std::bad_alloc
                    - image_load_error
                      This exception is thrown if there is some error that prevents
                      us from loading the given PNG file.
            !*/

            png_loader(
                const dlib::file& f
            );
            /*!
                ensures
                    - loads the PNG file with the given file name into this object
                throws
                    - std::bad_alloc
                    - image_load_error
                      This exception is thrown if there is some error that prevents
                      us from loading the given PNG file.
            !*/

            png_loader(
                const unsigned char* image_buffer,
                size_t buffer_size
            );
            /*!
                ensures
                    - loads the PNG from memory image_buffer of size buffer_size into this object
                throws
                    - image_load_error
                      This exception is thrown if there is some error that prevents
                      us from loading the given PNG buffer.
            !*/

            png_loader(
                std::istream& in
            );
            /*!
                ensures
                    - loads the PNG file from the c++ IO stream into this object
                throws
                    - image_load_error
                      This exception is thrown if there is some error that prevents
                      us from loading the given PNG buffer.
            !*/

            ~png_loader(
            );
            /*!
                ensures
                    - all resources associated with *this has been released
            !*/

            bool is_gray(
            ) const;
            /*!
                ensures
                    - if (this object contains a grayscale image without an alpha channel) then
                        - returns true
                    - else
                        - returns false
            !*/

            bool is_graya(
            ) const;
            /*!
                ensures
                    - if (this object contains a grayscale image with an alpha channel) then
                        - returns true
                    - else
                        - returns false
            !*/

            bool is_rgb(
            ) const;
            /*!
                ensures
                    - if (this object contains a 3 channel RGB image) then
                        - returns true
                    - else
                        - returns false
            !*/

            bool is_rgba(
            ) const;
            /*!
                ensures
                    - if (this object contains a 4 channel RGB alpha image) then
                        - returns true
                    - else
                        - returns false
            !*/

            unsigned int bit_depth (
            ) const;
            /*!
                ensures
                    - returns the number of bits per channel in the image contained by this
                      object.  The possible values are 8 or 16.
            !*/

            long nr (
            ) const;
            /*!
                ensures
                    - returns the number of rows (height) of the image contained by this
                      object.
            !*/

            long nc (
            ) const;
            /*!
                ensures
                    - returns the number of colums (width) of the image contained by this
                      object.
            !*/

            template<
                typename image_type
                >
            void get_image(
                image_type& img
            ) const;
            /*!
                requires
                    - image_type == an image object that implements the interface defined in
                      dlib/image_processing/generic_image.h
                ensures
                    - loads the PNG image stored in this object into img
            !*/

        };

    // ----------------------------------------------------------------------------------------

        template <
            typename image_type
            >
        void load_png (
            image_type& image,
            const std::string& file_name
        );
        /*!
            requires
                - image_type == an image object that implements the interface defined in
                  dlib/image_processing/generic_image.h
            ensures
                - performs: png_loader(file_name).get_image(image);
        !*/

    // ----------------------------------------------------------------------------------------

        template <
            typename image_type,
            typename Byte
            >
        void load_png (
            image_type& image,
            const Byte* image_buffer,
            size_t buffer_size
        );
        /*!
            requires
                - image_type == an image object that implements the interface defined in
                  dlib/image_processing/generic_image.h
                - Byte is either char, int8_t, uint8_t or std::byte
            ensures
                - performs: png_loader(image_buffer, buffer_size).get_image(image);
        !*/

    // ----------------------------------------------------------------------------------------

        template <
          class image_type
        >
        void load_png (
            image_type& img,
            std::istream& in
        );
        /*!
            requires
                - image_type == an image object that implements the interface defined in
                  dlib/image_processing/generic_image.h
                - in is an input stream containing a complete PNG encoded image
            ensures
                - Reads and ecodes the PNG file located in stream
        !*/

    // ----------------------------------------------------------------------------------------

    }

    #endif // DLIB_PNG_IMPORT_ABSTRACT