Downloading music coverart
Cover art has always been an important part of music. It is the way physical media is separated and recognized. Erven in today's digital world releases maintain a vast aesthetic and artistic connection to their cover art. From streaming apps to online web stores music is "visualized" using cover art.
In this article we will look at the implementation of a small library of mine written in Racket and discuss the differences between the various APIs used.
The APIs currently used are provided by iTunes, Last.fm, deezer and the Internet Archive - MusicBrainz collaboration service: Cover Art Archive.
iTunes Search API - This API returns 2 cover art URLs (sized 60x60 and 100x100). We can edit the URLs and get a cover art of any arbitrary size. There are also arguments for specifying the number of results needed and the explicitness of the results. This is a very powerful API and can be used for any kind of medium available in the iTunes store.
The library is using the following settings:
?term={TERM}&limit={LIMIT}&explicit={EXPLICIT}&media=music&entity=album
and provides the following functions:
(define (coverart:itunes term #:size [size 100] #:limit [limit 1] #:explicit [explicit #t]) ...)
This function searches iTunes for music albums and returns a list of URLs.
(define (coverart:itunes:simple artist release #:size [size 100] #:limit [limit 1] #:explicit [explicit #t]) ...)
This one is a wrapper function. It calls coverart:itunes with a properly formatted `term' based on the `artist' and `release' arguments.
Last.fm API - This API requires an API Key in order to respond. For the library's purposes the album.getInfo method is used. The URLs returned can have either of the following size field formats: Ys or YxY where Y is the resolution of the image. Editing the URL to request a specific resolution results in an image whose resolution is >= Y. Using the format YxY usually produces a wider range of results. Only one result is returned.
The following function is provided by the library and returns a string:
(define (coverart:lastfm artist release #:size [size 300] #:autocorrect [autocorrect #t]) ...)
deezer API - [You need to login to view the documentation] - Does NOT need an API key to use - This API returns 4 covert art URLs. The sizes are 56x56, 250x250, 500x500, 1000x1000. This service also allows editing the URL to get an image of any arbitrary resolution. Multiple results are returned and the number of results can be configured.
Here is the API URL used by the library:
http://api.deezer.com/search/album?q={QUERY}&nb_items={LIMIT}&output=json. Where
{QUERY} is the term you want to search for and {LIMIT} is the
number of results you want returned.
The two functions provided by the library are:
(define (coverart:deezer query #:size [size 1000] #:limit [limit 1]) ...)
This function searches deezer for cover art URLs and returns a list of them.
(define (coverart:deezer:simple artist release #:size [size 1000] #:limit [limit 1]) ...)
This is a wrapper function that calls coverart:deezer with the `query' argument formatted using the `artist' and `release'.
Cover Art Archive API - This is a very interesting service. It can return both the front and rear side of a medium's cover art and any accompanying booklets. There is one original image (of variable resolution) and three thumbnails (sized 250px, 500px and 1200px) available. The API requires a MusicBrainz ID to find and return a release's cover art.
This library provides three functions. One for searching MusicBrainz and getting an ID, one for searching Cover Art Archive and returning images and one that combines the previous two.
(define (musicbrainz:get-mbid query #:group-limit [group-limit 1] #:rel-limit [rel-limit 1])
This function searches MusicBrainz for IDs related to the `query' provided. The API organizes IDs in release groups. Each release group refers to a different album/EP/etc. Each group can have multiple releases. Each release has its own mbid. `#:group-limit' allows you to specify the maximum amount of release groups to return. `#:rel-limit' specifies the maximum number of releases included per release group. The function returns a list of lists of strings. The returned list contains one list for every release group. Each release group list contains strings of mbids to specific releases.
(define (coverartarchive:get-cover-url mbid #:type [type 'front] #:thumb [thumb #f])
Returns a list of cover art image URLs. `#:type' can be 'front to get the front part of the cover art, 'back to get the rear part, 'medium to get an image of the medium itself, 'booklet for images of the booklet included with the release or 'all to get all the images returned by the response. If `#:thumb' is specified with '|250|, '|500| or '|1200| a thumbnail is returned instead of the original image.
(define (coverart:coverartarchive artist release #:group-limit [group-limit 1] #:rel-limit [rel-limit 1] #:type [type 'front] #:thumb [thumb #f])
This function first calls musicbrainz:get-mbid using the `artist' and `release' arguments, then for every mbid returned coverartarchive:get-cover-url is called to get a list of URLs. It returns a list of lists of lists of strings. The returned list contains one list for every release group. Each release group list contains one list for every mbid. Each mbid list contains the image URLs related to that mbid.
In addition to those API specific functions, an additional function is provided to search all of the above APIs and return thumbnails to the cover art requested:
(define (coverart:search-thumb artist album #:size [size 500] #:fallback [fallback ""])
The function will call the APIs in this order: iTunes, deezer, Last.fm, Cover Art Archive. The ordering is based on a service's ability to resize the covers. For Cover Art Archive the `#:size' argument is ignored and a fixed width of 500px will always be returned (Possible future improvement). The value of the `#:fallback' argument is returned if none of the services produce a result. If a result is found the function returns a string.
Download the code [Racket]: coverart.rkt
License: BSD 3-Clause