Clarify requirements for cover images and thumbnails

[GoogleCodeExporter]

Please review, clarify, and supplement the section of the specification that 
covers the purpose, constraints, and markup for cover image thumbnails (and 
other sizes).

Please note that any discussion should happen on the mailing list rather
than the comments of the issue tracker.

Mailing list threads should reference the number of any open Issue in the
Subject line " (#ISSUE)".

Original issue reported on code.google.com by abdela...@gmail.com on 12 Mar 2010 at 3:04

[GoogleCodeExporter]

Original comment by liza31337@gmail.com on 3 May 2010 at 2:05

[GoogleCodeExporter]

Catalog implementers are encouraged to include book cover images in their feeds 
as atom:link elements.  
It is also recommended to include a properly-sized "thumbnail" image of the 
same cover, for use in lists 
of items.

Cover images and thumbnails are not required.  If they are included they MUST 
use the following link 
relations:

  * http://opds-spec.org/cover
  * http://opds-spec.org/thumbnail

Per the Atom specification they also MUST include the correct content type for 
the image file.

Images SHOULD be in one of the following formats:

  * PNG (image/png)
  * JPEG (image/jpeg)
  * GIF (image/gif)

To provide the cleanest appearance and best interoperability, it is recommended 
that thumbnails should 
be no wider than 100px. A width/height ratio of 0.75 is preferred. 

{{{
   <link type="image/png" rel="http://opds-spec.org/cover"           href="http://opds-
spec.org/covers/4561.lrg.png"/>
    <link type="image/png" rel="http://opds-spec.org/thumbnail" href="http://opds-
spec.org/covers/4561.thmb.png"/>
}}}

Original comment by liza31337@gmail.com on 3 May 2010 at 2:12

• Changed state: Started

[GoogleCodeExporter]

+== Covers and Artwork ==
+
+OPDS Catalog Entries MAY include relations to images that provide a visual 
representation of the electronic 
publication. For many publications, these images will be the publication's 
cover or other distinguishing 
artwork. 
+
+Catalog Entries MUST use one of the following link relations for these images:
+
+  * "http://opds-spec.org/cover": a high-quality version of the image 
+  * "http://opds-spec.org/thumbnail": a version of the image suitable for 
presentation at a small size
+
+The maximum size of the longest dimension of http://opds-spec.org/thumbnail 
images SHOULD be 120 
pixels.
+
+The atom:links with these relations MUST include a type attribute of 
"image/gif", "image/jpeg", or 
"image/png" and the image resources MUST be in GIF, JPEG, or PNG format.
+
+While either image resource is optional and may be included independently, 
OPDS Catalog providers are 
encouraged to provide both these relations and resources whenever possible. 
More than one atom:link with 
either relation SHOULD NOT be provided for a single OPDS Catalog Entry.
+

Original comment by abdela...@gmail.com on 4 May 2010 at 5:44

• Changed state: Done

[GoogleCodeExporter]

+Some OPDS Catalog providers MAY choose to provide 
http://opds-spec.org/thumbnail image resources using 
the "data" URL scheme from `[RFC2397]`. OPDS Catalog clients SHOULD support the 
"data" URL scheme if they 
support Covers and Artwork relations.

Original comment by abdela...@gmail.com on 4 May 2010 at 6:27

[GoogleCodeExporter]

Original comment by abdela...@gmail.com on 25 May 2010 at 5:44

• Added labels: Milestone-Release0.9