An annotation is a new layer introduced by the reader for reading comfort and note making. The usual annotation facilities are 'adding a comment','highlighting a selected part of the text' and ‘rectangle tool’. As annotation standards were being established, the annotation file was kept as a separate markup file. As they became more standardized, they were integrated as a part of the document. As with the success of any new feature (or version of a protocol or document specification), it depends on the implementation in the ‘reader’. In case of PDF, this happened rapidly during the recent years.
But, in DJVU readers, the annotation feature seems to be poorly implemented. There are two aspects of this implementation:
- capability to ‘read’ the annotation.
- capability to create an annotation.
Unfortunately, most DJVU readers seem to have not implemented or not completely implemented or ambiguously implemented the annotation features.
Lets take ‘WinDjView’ for example. It is probably the most used reader (not just in windows OS — Its run on linux via wine too). ‘WinDjView’ 2.02 does not read all types of annotations.
The list of annotations:
- Highlight Areas
- Rectangular Hyperlinks
- Oval Hyperlinks
- Polygon Hyperlinks
- Text Annotations
- Line Annotations
- Headers (for printing but not for display)
- Footers (for printing but not for display)
It only reads ‘highlight areas’ and ‘rectangular hyperlinks’ (not implemented or incompletely implemented). ‘WinDjView’ 2.02 allows you to create a ‘highlight area’ annotation, but this is stored on your computer and it is not the part of the file. (ambiguously implemented)
Annotation functionality is not the part of ‘djvulibre’ package and this might be the reason for the poor implementation. This limits any reader that depends on the package like ‘WinDjView’ 2.02.
I hope, at least a few annotation features can be made standard as it raises the comfort standards by a huge margin.
PS: As of now, one can use DJVU editor (by Lizardtech/Caminova) post version 6 to create and read annotations. A copy of this can be found in files page of scan kromsator :) (Yes, I am avoiding links on purpose)
— 18 Jan 2014 09:55