NAME
    XAO::ImageCache - Images caching by URLs stored in XAO::FS database

SYNOPSIS
        use XAO::ImageCache;

        # Making new instance of Image Cache object
        my $image_Cache = XAO::ImageCache->new(
            list           => $odb->fetch("/Products"),
            cache_path     => "/var/httpd/shop/product/images/",
            cache_url      => "/products/images/",
            source_url_key => "source_img",
        ) || die "Can't make Image cache!";

        # Init new empty Cache
        $image_cache->init() || die "Can't init new cache!";

        # Start images checking and downloading to cache
        $image_cache->check();

DESCRIPTION
    When we store images links on own database we have no real images on own
    site. Some time it may be a problem cause images may have no right
    dimension or may be deleted from source site.

    XAO::ImageCache made for cache locally images his URL stored in XAO
    Founsation Server. Also, images may be resized automaticaly.

    This module provide easy methods to scan XAO Foundation Server data
    lists, to extract images source URLs from data objects, to download
    images to local cache, to resize a local copy of the image to fit into
    given dimensions and to store the new local URL of the image back to the
    data object.

METHODS
    new($%)
        The constructor returns a new "XAO::ImageCache" object. You can use
        it to make new images cache or check images of already existent
        cache.

         my $image_cache = XAO::ImageCache->new(
             cache_path     => "cache",         # set cache directory to './cache/'
             source_path    => "cache/source",  # set source directory to './cache/source/'
             local_path     => "images/copy",   # (optional) try to resolve local urls
             cache_url      => "images/",       # set cached images (relative) path to 'images/'
             list           => $odb->fetch("/Products"),
             source_url_key => 'source_image_url',
             dest_url_key   => 'dest_image_url',
             filename_key   => 'product_id',
             min_width      => 50,              # Source image is ignored if smaller
             min_height     => 50,
             size           => {
                 width  => 320,
                 height => 200,
                 save_aspect_ratio => 1,
             },
             thumbnails     => {
                 path     => '/var/httpd/shop/product/images/tbn',
                 url      => '/products/images/tbn/'
                 geometry => "25%",
                 url_key  => 'thumbnail_url',
             },
             autocreate     => 1,
             useragent      => {
                 agent   => 'My Lovely Browser/v13.01',
                 timeout => 30,
             },
             force_download => 1,               # to enforce re-downloads
             force_scale    => 1,               # to enforce re-scaling
             clear_on_error => 0,               # don't clear DB properties even on permanent errors
         ) || die "Image cache creation failure!";

        A number of configuration parameters can be passed to
        XAO::ImageCache to tune functionality.

        autocreate
        cache_path
        cache_url
        clear_on_error
        dest_url_key
        force_download
        force_scale
        list
        source_url_key
        size
        thumbnails
        useragent

        Follow to CONFIGURATION PARAMETERS section to see what each
        parameter does.

        If any required parameter is not present an error will be thrown.

    init($)
        Cache structure initialization.

        Executed automaticaly if "autocreate" parameter present.

        Create image cache directory if non existent and thumbnail cache
        directory if non existent and defined as initialization parameter.

    check($)
        Goes through given XAO FS data list, downloads images from source
        url to cache and puts cache url into destination url key and
        thumbnail url key (where applicable).

        XAO::ImageCache->download() will be executed for downloading each
        image.

    download($$)
        Downloads image into cache directory.

        If "thumbnails" contains "cache_path" parameter, thumbnail is either
        downloaded into thumbnail cache directory or created from downloaded
        image.

        Source image URL should be passed as parameter. Source thumbnail URL
        is an optional parameter:

            $img_cache->download($image_source_url, $thumbnail_source_url);

        Downloaded image is resized if "size" parameter present. Thumbnail
        is resized as specified by "thumbnails" "geometry" parameter.

        When "force_download" configuration parameter is not set to True
        value, image will be downloaded into cache only if image is not
        already cached or if cached image has a later modification date than
        source image.

    scale_large($$$)
        Scaling image to given size.

    scale_thumbnail($$$)
        Creates thumbnail image from given source image.

    remove_cache($)
        Removing the ENTIRE cache directory from disk.

        Be carefully to use this method!!!

        Cache structure will be removed from disk completely! Set
        "force_download" parameter to True value to download images to cache
        without any conditions.

    get_filename($)
        File name generation for cached images.

        Source image URL should be passed. Returned file name is an MD5
        digest of the source URL converted to Base64 string with all non
        alpha numeric characters are converted to "_".

        Example.

            Location:
            http://localhost/icons/medbutton.jpeg

            provide file name:
            4aFNA1utpmCNG2wEIF69mg.jpeg

    treat_filename($)
        Makes sure only file name friendly characters are present: all non
        alpha numeric characters are converted to "_".

CONFIGURATION PARAMETERS
    The set of configuration parameters contain required and optional
    parameters.

    Required parameters should be defined. Execution will be stoped if
    required parameter not present.

    Optional parameters just configure aditional functionality and may not
    present.

  Required parameters
    cache_path
        - Path string where the cache should be placed.

        May be absolute or relative from current execution directory path.

        For example. Set it to "./cache" if you whant to place cache in
        "cache" subdirectory of your script working directory.

    cache_url
        - complet URL (or relative location) to cached images.

        Place here your URL reflection of cache directory in condition with
        your HTTP server configuration.

        For example. Set it to "http://my.host.com/images/" if your HTTP
        server configured for provide access to your cache directory by
        hostname "my.host.com" and location "images/". Cached images names
        will be added to image URL automaticaly.

    list
        - reference to "XAO::DO::FS::List" object containing the data
        objects with Image source URL

        Meaning, your data look like a XAO Foundation Server list of objects
        with references to images. This parameter should contain reference
        to to XAO::DO::FS::List object. This reference may be result of
        XAO::Objects->fetch() methode.

        XAO::ImageCache will process each record of this list.

    source_url_key
        - data key containing the URL of source image.

        Contain the name of key of data object containing the source image
        reference.

  Optional parameters
    dest_url_key
        - data key for storing URL of image in cache.

        Optional parameter cause image name in cache will be a MD5 Base64
        digest of source image path where "=" character removed, "\" and "+"
        translated to "_" and "-" simultaniosely.

        To get cached image name

    size
        - Prefered image size may set as "geometry" equal to "geometry"
        parameter of Image::Magick module to pass it dirrectly to
        Image::Magick Scale function.

        Other way to set the image size is set a width and height keys to
        preffered values.

        If one of image dimension is not defined then corresponding
        parameter of original image will be used.

        This way, image will be resized with same aspect ratio (same
        proportions) to the original image if "save_aspect_ratio" parameter
        present.

        Image width and height will be resized exactly to given size if
        "save_aspect_ratio" parameter not present.

        Parameter "geometry" has higher priority and other parameters has no
        effects if "geometry" peresent.

        For example.

            # Size 320x200 as geometry settings
            %params = (size => {geometry => "320x200!"} );

            # Size 320x200 as dimensions settings
            %params = (size => {width => 320, height => 200} );

            # Fit size into 320x200 with saving image proportions
            %params = (
                size => {
                    width                   => 320,
                    height                   => 200,
                    save_aspect_ratio => 1,
                }
            );

    autocreate
        - create or check cache content automaticaly.

        If non zero value present, cache directory will be created and
        images checking will be runned. Otherwithe you should run init() and
        check() methodes manualy.

        Existent cache directory will not be removed. You may do it manualy
        using remove_cache() methode.

    force_download
        - each image should be reloaded to cache and processed without
        dependance of source image modification time. Any conditions
        ignored.

    thumbnail
        - thumbnails creator configuration

        Some thubnails configuration parameters may be set for automatic
        thumbnails creation. This parameter should contain the reference to
        hash with thumbnails configuration parameters.

        Only "path" parameter is required. Other parameters are optional.

        path
            path where thumbnail images should be placed.

        url URL for access to thumbnails directory. Same way as "cache_url".

        url_key
            Data object key name where thumbnail URL should be stored.

        geometry
            Geometry string to set thumbnail images size in Image Magick
            geometry format. May be set as dimension ("320x200!") or as
            persent of actual size of cached image ("25%").

            Default value is "50%" the half of actual image size.

    useragent
        - configuration parameters hash for LWP::UserAgent

        agent
            Default value "XAO-ImageCache/#.##"

        env_proxy
            Default value 1

        keep_alive
            Default value 1

        timeout
            Default value 30

        For more information please follow to LWP::UserAgent

SEE ALSO
    Specifics of List API can be found in

    XAO::DO::FS::List.

    For additional information please see

    XAO::DO::FS::Glue,

    XAO::DO::FS::Global,

    XAO::DO::FS::Glue::MySQL_DBI,

    Refer to Image::Magick documentation for additional information about
    setting of image scaling parameters.

    Refer to LWP::UserAgent documentation for additional information about
    user agent parameters.

BUGS
    Please, inform me about found bugs.

AUTHORS
    The XAO::ImageCache package maintained by Konstantin Safronov
    <skv@xao.com>. Specification by Andrew Maltsew <am@xao.com>

