nsdejavu - DjVu browser plugin
The shared library nsdejavu.so uses the Netscape browser plugin API to display DjVu images in in a number of popular web browsers. Different web browsers provide various level of support for Netscape plugins. Please check section "Browser Compatibility" for instructions on how to enable the DjVu browser plugin.
The DjVuLibre browser plugin works by invoking a standalone viewer with the special command line option -netscape. The plugin first searches a program named djview. If this program cannot be found, it searches for djview4 and finally djview3. It is always possible to override this search strategy by setting the environment variable NPX_DJVIEW to the full path of the desired executable.
MIME TYPES AND EXTENSIONS¶
Typing the URL of a recognized DjVu document in your web browser should automatically invoke the DjVu browser plugin. Each browser uses different methods to determine that a particular URL is in fact a DjVu document. Web server normally provide a MIME type to web browsers. The official MIME type for DjVu documents is image/vnd.djvu. For compatibility with ancient versions of the DjVu viewer, it is common to use instead the experimental MIME type image/x-djvu or image/x.djvu. Web servers should be configured to send the proper MIME type for DjVu documents. Most web browsers also recognize files ending with .djvu or .djv as DjVu files.
An easy way to check if an http server is giving an appropriate content-type is to invoke the following command with a URL corresponding to an actual DjVu file on the server.
- curl -u URL | grep Content-Type
The result should be one of the following, preferably the first.
- Content-Type: image/vnd.djvu
Any other MIME type indicates a server misconfiguration.
The behavior of the DjVu browser plugin can be specified by augmenting the URL using a syntax similar to that used by the CGI programs. This syntax is described by the following template:
The DjVu browser plugin only recognizes keywords that appear after the word djvuopts. The keywords recognized by each viewer are listed in the corresponding man page. Unrecognized keywords are ignored. The most common keywords are:
- Specify which page is displayed by name or by ordinal number.
- Set the zoom factor. Legal values for zoomfactor are:
number Magnification factor in range 10% to 999%. one2one Select the "one-to-one" mode. width Select the "fit width" mode. page Select the "fit page" mode. stretch Stretch the image to the plugin window size.
The DjVu browser plugin has been tested with several popular web browsers: Netscape 4 and 6; Gecko based browsers such as Mozilla, Galeon and Firefox; KHTML based browsers such as Konqueror; and Opera. Please read the browser documentation to find out where the plugin library should be installed.
EMBEDDING DJVU IMAGES IN HTML PAGES¶
You can integrate DjVu content on an HTML web page with either the <embed> or the <object> tag. This method will work even if your web server does not support the DjVu MIME type. The CGI style flags can be directly used as attributes of the embedding tag. The following example shows the W3C standard syntax with the OBJECT tag:
- <object data="myfile.djvu"
width="100%" height="100%" >
<param name="page" value="iii">
<param name="zoom" value="stretch">
This browser cannot render djvu data.
And this is the customary syntax with the EMBED tag:
- <embed src="myfile.djvu"
- Set the value of the djvu option key to the character string value. This achieves the same effect as specifying option key=value among the CGI-style flags. For instance, values of the key page can be page IDs, page titles, page numbers, or page names.
- Return the value of the djvu option key as a string. The returned value is always a character string, even when the return is logically a number. Boolean values are returned as strings yes or no. Besides the usual CGI-style flags, this function recognizes the additional key pages and returns the total number of pages in the DjVu document. An empty string is returned when the key is not recognized.
- Ensure that string code is evaluated in the context of the plugin object whenever something changes in the djview graphical user interface. For instance, this evaluation happens when progressive refinements are painted, and when the user manipulates the image interactively.
- Return a string describing the plugin version. This property can be used to test whether the djview plugin is scriptable in this browser.
This program was written by Andrei Erofeev <firstname.lastname@example.org> and was then improved by Bill Riemers <email@example.com> and Léon Bottou <firstname.lastname@example.org>.