ACS 4 Photo Album Package Design Documentation
by Tom Baginski,
bags@arsdigita.com
Essentials
User accessible directory depends on where package is mounted
in site.
No separate administration directories
Tcl procedures: packages/photo-album/tcl/photo-album-procs.tcl
(link to proc depends on install)
Data model: packages/photo-album/sql/photo-album-create.sql
(link to data model depends on install)
Introduction
The basic content element of the photo album system is a photo.
When a user uploads a photo, the system stores attribute
data such as caption, story, and title as a
single content element. Each photo associated with several
(three to start) image elements that store the actual binary files.
The image elements, which are created by the server, are standard sized
versions of the original photo used for display. Photos and images
can have descriptive attributes associated with them. The attributes
and binary files can be revised and the system will retain past
versions.
Photos are grouped together into albums which can contain 0 or
more photos. The albums can have descriptive attribute information
that can be revised with history tracking. The albums can be
displayed as a unit that allows user to browse through the photos
in the album.
Albums can be grouped together into folders that can contain 0
or more albums or other folders.
An instance of the package include pages to display the folders,
albums, and photos along with admin pages. Instances can be mounted
to different subsite and managed independently. The grouping is
included within the instance so that the albums maintain a
consistent url even if they are re-sorted to different folders
within the instance (as long as the subsite url isn't changed).
The display, grouping, and administration functionality of the
photo album package will be included in the initial release of the
package. This is intended to be one part of a larger system that
will allow bulk uploading and purchasing of photos. These two
feature have already been implemented on aD customer sites. ACS 4
versions of these features will be either incorporated into a
future version of the photo album package or added as individual
packages that depend on the photo album.
The basic tasks of the photo album revolve around storing and
displaying content and associated attributes. As such, this package
will take advantage of the exiting features of the content
repository service package. The content repository can store
multiple revisions of content items such as photos and images and
their associated attributes. The content repository also provides
grouping functions. The acs permission service will be used for
access control so view, edit, and administration privileges will be
highly customizable. Finally individual photo album instances can
be added to subsites to support multiple independent photo albums
on the same site.
Historical Considerations
The the development of photo album package was base largely on
the experience of building a custom photo album application for the
Iluvcamp client site. The Iluvcamp photo album was built using an
early version of the content repository. The photo album package
uses the current version of the ACS content repository and takes
advantage of several key features of the ACS4 structure such as
permissions, templating, the content repository. The photo album
package avoid several of the limitation of the Iluvcamp Photo Album
that were made clear after supporting a summer of use and uploading
over 70GB of original photos.
A photodb application was developed for ACS 3.x. The option of
porting the photodb application to ACS4 was not followed due to the
customized nature of the photodb application. It was primarily
designed for storing and displaying information about photos for
photographers. In contrast, the photo album application provides a
general system for storing and displaying user uploaded photos,
which can be customized to any particular client application.
Competitive Analysis
Not done. A google search for "photo album web application"
returns links for several shareware photo album applications.
I did not install or test any of these.
Design Tradeoffs
The package uses/requires the convert and identify
ImageMagick
binaries to be installed on the host computer at the location
specified in the ImageMagickPath parameter. ImageMagick is readily
available and easy to use from within server pages. ImageMagick is
copyrighted by ImageMagick Studio, a nonprofit organization.
ImageMagick is available for free, may be used to support both open
and proprietary applications, and may be redistributed without fee.
The previous ImageMagick Homepage has some mention of LZW patent
issues and redirects to a new location. If these patent issues
become a problem, the package will need to be re-coded to use
different image manipulation software.
By default the package stores the image binary files in the file
system. This decision was made for ease of use and development.
This was also based on the assumption that file system storage is
more appropriate for large systems with many giga-bytes of photos.
The content repository also provides support for database storage
of binaries in blobs. Future version of the photo album will also
support database storage of photos. Load testing will be used to
determine the most appropriate storage method for small and large
volumes of photos.
The default photo storage directory is outside of the page root
and images are served using a .vuh file. This was done to prevent
potential execution of user uploaded files. Although the package
checks that the user only uploads image files, in theory a rouge
user could upload a code file. If that file was directly accessible
from the page root, the rouge user could execute arbitrary code
with all the authority of the web server user. Serving the image
through a .vuh file also allows for checking access permissions to
a file before it is served to the user. The benefits of serving
image files with a .vuh file comes at a cost of some additional
server resources. Again, load testing will be used to determine the
true cost of using a .vuh file.
The photo attribute information and binary files are stored in
two different content types (pa_photos and pa_images). The linkage
between the binaries and the attribute info is maintained as a
relationship between the two content_items. This decision was made
so the the number of image sizes per photo could be changed with minor
code revision and no datamodel changes. This flexibility comes at a
cost, the queries to retrieve and serve the appropriate version of
a photo need to join in several tables to do so. There also is not
an easy way to store the relation between different versions of the
photo-attribute info such as caption and the versions of the binaries.
API
PL/SQL API
The PL/SQL database api is incorporated into four packages: pa_image,
pa_photo, pa_album, and photo_album. The first three correspond to the
3 new object types created for the photo album application. The last
contains general database functions for the application.
pa_image package
pa_image.new creates a new pa_image object type and returns the
cr_item.item_id of the newly created object. It also create the first revision
of that object. It accepts an item_id and revision_id as arguments but both
will be created if not provided. Although relation tag defaults to null it
should be in (thumb, viewer, base). Path is the path to the image binary relative
to the upload base (a parameterized directory).
function new (
name in cr_items.name%TYPE,
parent_id in cr_items.parent_id%TYPE default null,
item_id in acs_objects.object_id%TYPE default null,
revision_id in acs_objects.object_id%TYPE default null,
content_type in acs_object_types.object_type%TYPE default 'pa_image',
creation_date in acs_objects.creation_date%TYPE default sysdate,
creation_user in acs_objects.creation_user%TYPE default null,
creation_ip in acs_objects.creation_ip%TYPE default null,
locale in cr_items.locale%TYPE default null,
context_id in acs_objects.context_id%TYPE default null,
title in cr_revisions.title%TYPE default null,
description in cr_revisions.description%TYPE default null,
mime_type in cr_revisions.mime_type%TYPE default null,
nls_language in cr_revisions.nls_language%TYPE default null,
relation_tag in cr_child_rels.relation_tag%TYPE default null,
is_live in char default 'f',
publish_date in cr_revisions.publish_date%TYPE default sysdate,
path in pa_images.path%TYPE,
height in pa_images.height%TYPE default null,
width in pa_images.width%TYPE default null,
file_size in pa_images.file_size%TYPE default null
) return cr_items.item_id%TYPE;
pa_image.delte_revision deletes a specified revision
of a pa_image and schedules the binary for deleation from the file-system by a sweep procedure
procedure delete_revision (
revision_id in cr_revisions.revision_id%TYPE
);
pa_image.delete deletes a pa_image and all revisions
Also schedules the binary files for deletion from the file-system.
procedure delete (
item_id in cr_items.item_id%TYPE
);
pa_photo package
pa_photo.new create a new pa_photo object
and returns the cr_item.item_id of the new object. Also creates first revision of object
function new (
name in cr_items.name%TYPE,
parent_id in cr_items.parent_id%TYPE default null,
item_id in acs_objects.object_id%TYPE default null,
revision_id in acs_objects.object_id%TYPE default null,
content_type in acs_object_types.object_type%TYPE default 'pa_photo',
creation_date in acs_objects.creation_date%TYPE default sysdate,
creation_user in acs_objects.creation_user%TYPE default null,
creation_ip in acs_objects.creation_ip%TYPE default null,
locale in cr_items.locale%TYPE default null,
context_id in acs_objects.context_id%TYPE default null,
title in cr_revisions.title%TYPE default null,
description in cr_revisions.description%TYPE default null,
relation_tag in cr_child_rels.relation_tag%TYPE default null,
is_live in char default 'f',
publish_date in cr_revisions.publish_date%TYPE default sysdate,
mime_type in cr_revisions.mime_type%TYPE default null,
nls_language in cr_revisions.nls_language%TYPE default null,
caption in pa_photos.caption%TYPE default null,
story in pa_photos.story%TYPE default null,
user_filename in pa_photos.user_filename%TYPE default null
) return cr_items.item_id%TYPE;
pa_photo.delete_revision deletes a specified
revision of a pa_photo
procedure delete_revision (
revision_id in acs_objects.object_id%TYPE
);
pa_photo.delete deletes a pa_photo object,
all revision of a pa_photo, and all associated pa_images (including binaries). Basically nukes
a photo, so be careful using this one, because it can't be undone.
procedure delete (
item_id in acs_objects.object_id%TYPE
);
pa_album package
pa_album.new creates a new pa_album object type and returns the
cr_item.item_id of the newly created object. It also create the first revision
of that object. It accepts an item_id and revision_id as arguments but both
will be created if not provided.
function new (
name in cr_items.name%TYPE,
album_id in cr_items.item_id%TYPE default null,
parent_id in cr_items.parent_id%TYPE default null,
revision_id in cr_revisions.revision_id%TYPE default null,
content_type in acs_object_types.object_type%TYPE default 'pa_album',
is_live in char default 'f',
creation_date in acs_objects.creation_date%TYPE default sysdate,
creation_user in acs_objects.creation_user%TYPE default null,
creation_ip in acs_objects.creation_ip%TYPE default null,
locale in cr_items.locale%TYPE default null,
context_id in acs_objects.context_id%TYPE default null,
relation_tag in cr_child_rels.relation_tag%TYPE default null,
publish_date in cr_revisions.publish_date%TYPE default sysdate,
mime_type in cr_revisions.mime_type%TYPE default null,
nls_language in cr_revisions.nls_language%TYPE default null,
title in cr_revisions.title%TYPE default null,
description in cr_revisions.description%TYPE default null,
story in pa_albums.story%TYPE default null
) return cr_items.item_id%TYPE;
pa_album.delte_revision deletes a specified revision
of a pa_album
procedure delete_revision (
revision_id in cr_revisions.revision_id%TYPE
);
pa_album.delete deletes a pa_album and all revisions
of that album. The album must not have any child pa_phots or the delete throws an error. So
there is nothing equilent to rm -r *. You separately delete the
photos in an album (or move them to a different album) then delete the album.
procedure delete (
album_id in cr_items.item_id%TYPE
);
photo_album package
photo_album.get_root_folder returns the root folder
for a given package_id (package instance). The root folder for a package is actually cached by the
web server. So it is probably faster to call the server proc pa_get_root_folder and pass the value
in as a bind variable any place you need the root_folder in a query.
function get_root_folder (
package_id in apm_packages.package_id%TYPE
) return pa_package_root_folder_map.folder_id%TYPE;
Procedural API
The public procedural API available from the webserver is currently
implemented as tcl procedures.
pa_get_root_folder {package_id ""}
Returns the folder_id of the root folder for an instance of the photo album system.
If no root folder exists, as when a new package instance is accessed for the first time,
a new root folder is created automatically with appropriate permissions
If value has be previously requested, value pulled from cache. If pakage_id is not specified,
procedure uses value from [ad_conn package_id]
pa_context_bar_list {-final ""} item_id
Constructs the list to be fed to ad_context_bar appropriate for
item_id. If -final is specified, that string will be the last
item in the context bar. Otherwise, the name corresponding to
item_id will be used.
pa_make_file_name {-assert:boolean} {-ext ""} id
Constructs a filename for an image based on id and extension.
Files are created into a 3 tier directory structure: year/xx/zz/ for a photo_id 1234xxzz.jpg
Same file would return year/xx/zz/1234xxzz.jpg.
If -assert specified, proc creates directory and any parent directories if necessary
pa_is_folder_p folder_id {package_id ""}
Returns "t" if folder_id is a folder that is a child of the root folder for the package,
else "f". If package_id is not given procedure uses value from
[ad_conn package_id].
pa_is_album_p album_id {package_id ""}
Returns "t" if album_id is a album that is a child of the root folder for the package,
else "f" If package_id is not given procedure uses value from
[ad_conn package_id].
pa_is_photo_p photo_id {package_id ""}
Returns "t" if photo_id is a photo that is a child of the root folder for the package,
else "f" If package_id is not given procedure uses value from
[ad_conn package_id].
pa_grant_privilege_to_creator object_id {user_id ""}
Grants a set of default privileges stored in parameter PrivilegeForCreator
on object id to user_id. If user_id is not specified, uses current user.
pa_image_width_height filename width_var height_var
Uses ImageMagick program to get the width and height in pixels of filename.
Sets height to the variable named in height_var in the calling level.
Sets width_var to the variable named in width_var in the calling level.
I Use ImageMagick instead of aolsever funcition because it can handle more than
just gifs and jpegs.
pa_make_new_image base_image new_image max_width {max_height ""}
Uses ImageMagick program to create a file named new_image from base_image that
fits within a box defined by max_width by max_height (in pixels).
ImageMagick will retain the aspect ratio of the base_image when creating the new_image
If max_height is not specified, max_width is used for max_height.
pa_all_photos_in_album album_id
Returns a list of all the photo_ids in an album sorted in ascending order.
Pulls value from cache if already there, caches result and returns result if not
pa_count_photos_in_album album_id
Returns count of number of photos in album_id
pa_all_photos_on_page album_id page
Returns a list of the photo_ids on page page of album_id.
List is in ascending order
pa_count_pages_in_album album_id
Returns the number of pages in album_id
pa_page_of_photo_in_album photo_id album_id
Returns the page number of a photo in an album. If photo is not in the album returns -1
pa_flush_photo_in_album_cache album_id
Clears the cacheed value set by pa_all_photos_in_album for a single album
Call proc on any page that alters the number or order of photos in an album.
pa_pagination_page_number_links page total_pages
Returns html table fragament for navigating pages of an album.
pa_photo_number_links cur_id all_ids
Given a current photo_id and and an ordered list of all the photo_id in an album,
creates an html fragment that allows user to navigate to any photo by number,
or next/previous. Pulls url from connection so should work on page showing a single photo
based on photo_id (such as viewer size display page or base size display page).
Data Model Discussion
The data model defines 3 new content types within the content
repository. These are pa_album, pa_photo, and pa_image. It uses the
exiting content_folder for grouping pa_albums. Pa_albums store
attribute information about a group of photos and serves as a
container for 0 or more photos. Pa_photos store attributes of user uploaded
photo. Pa_images are used as a helper type to store the base (original),
thumbnail and viewer display images associated
with a pa_photo. Each pa_photo has one child pa_image for its
base photo, one for its thumbnail image, and one child pa_image for its viewer image. The
pa_images are created by the server whenever a pa_photo is added
or edited.
The root folder for each package instance is stored in pa_root_folder_package_map.
All folders, albums, photos, and images within a package instance are
descendants of the root folder for that package.
Image files scheduled for deletion are stored in pa_files_to_delete. A
nightly web-server process deletes the files in this table and then removes
them from the table. This table allows images to be deleted transactionally from
both the database and the file-system. All photo/image delete operations should
add the binary file-name to pa_files_to_delete and then delete the attribute information
in the database within a transaction. This way the file system delete will not
happen unless the database delete succeeds.
User Interface
The user accessible pages contain a set of pages for displaying,
adding, and editing folders, albums, and photos. The folder page
which serves as the index page allows a user to navigate to
sub-folders and albums within the folder. The album page displays
the photos (or a sub-set of photos) within an album. The photo page
displays a single photo.
Configuration/Parameters
Parameters are set by default through the apm and can be
edited by a user with admin privileges for a sub-site through the
current sub-site admin pages. Depending on which version of the
apm is installed, the server may need to be restarted for
the parameters of a new package instance are available.
The defined parameters are as follows:
ImageMagickPath
Description: Absolute path from computer root to directory
containing ImageMagick executables convert and identify.
Default: /usr/local/bin
PhotoDir
Description: Relative path from acs_root_dir to directory for
storing uploaded images. (do not include leading or trailing
forward slash)
Default: uploaded-photos
FullTempDir
Description: Absolute path from computer root to path for
temporary photos.
Default: /tmp/photo-album
PhotoStorageMethod
Description: Default method for storing photos, file-system or
database. (Package currently only supports file-system)
Default: file-system
ThumbnailSize
Description: Max Dimension for thumbnail image
Default: 100
ViewerSize
Description: Max Dimension for viewer images
Default: 400
ThumbnailsPerPage
Description: Number of thumbnail images to be displayed per album
page
Default: 12
PrivilegeForCreator
Description: CSV of privileges to grant to creators of new objects
within photo album
Default: admin
AcceptableUploadMIMETypes
Description: CSV of acceptable MIME Types for Photo Upload
Default: image/jpeg,image/gif
DefaultRootFolderPrivileges
Description: List of grantee privilege pairs for new root folders.
Grantee is an integer or function that returns a party_id. Format
as a space separated list
Default: acs.magic_object_id('the_public') read
acs.magic_object_id('registered_users') pa_create_album
acs.magic_object_id('registered_users') pa_create_folder
AllowBasePhotoAccessP
Description: If set to "t", users are presented a link to
display the full sized base image from photo page.
Default: t
CheckPermissionOnImageServeP
If set to "t", the images/index.vuh file runs a query to check
if user has read access to photo prior to serving it. Note, setting to
"t" can impact performance on high volume sites. The urls for images
also change depending on this parameter. If "t" url contains the
pa_image_id, else contains the path to the pa_image in file-system.
Default: f
Future Improvements/Areas of Likely Change
Server backed image manipulation
Purchase and printing of photo through ecommerce package and
photo printing vendor.
Bulk upload tool
User specified attributes
Upload quotas
Admin notification of file space limitations.
Search and retrieval of photos and albums based on attributes
or key words.
Admin specified attributes
Authors
System creator, System owner, and Documentation author: Tom
Baginski, bags@arsdigita.com
Revision History
Document Revision #
Action Taken, Notes
When?
By Whom?
0.1
Creation
12/17/2000
Tom Baginski
0.2
Editing
1/9/2001
Tom Baginski
0.3
Editing and additions to API and Data Model sections.
2/5/2001
Tom Baginski
bags@arsdigita.com