With the DjVu™ Web Browser Plug-in 3.2, any Internet user can view highly-detailed color pages of books, magazines, catalogs, manuals, even historical documents, in full, vivid detail that's a pleasure to read and lightening-fast to download. The DjVu Web Browser Plug-in harnesses the power of the DjVu imaging language to allow any personal computer user to view the most advanced image files available.
DjVu documents, when zoomed to sizes larger than the display window, can be scrolled whenever you see the hand cursor. Click on the document, move the mouse, then unclick. You can also scroll the document using the scroll bars at the right and bottom of the document, or by using Up, Down, Left, and Right keyboard shortcuts.
The pop-up toolbar is located at the bottom of the plug-in's window. It provides shortcuts to the most often executed operations such as display modes, zooming, and navigating through multipage DjVu documents.
The toolbar is always visible and enabled. To make the toolbar auto hide or disable, you can use the Preferences.
The DjVu Toolbar gets disabled for embedded images if the window size is too small to fit the Toolbar.
Most DjVu files contain images stored in more than one layer. There may be several background layers, a mask layer, and a foreground layer. By switching between different display modes, one can see what is stored in each layer:
Display Mode |
Description |
Color mode |
All layers are visible. |
Background mode |
Only background layers are visible. Background layers store the images and paper color (BG44, BGjp). |
Foreground mode |
Only the foreground layers are visible. Foreground layers store the color of the text (FG44, FGjp) and masked by mask layer is visible. |
Black and White mode |
Only the mask layer, which typically stores text in black (Sjbz, Smmr), is visible. |
In order to change the display mode, select the desired mode from the Display item on toolbar.
The zoom factor (magnification) can be any number from 5% to 999% and refers to the magnification of the physical dimensions of the image. The plug-in tries to compute the actual scaling coefficients taking into account the display and image DPI (Dots Per Inch) information. For example, if you display a page at 100% then it should appear approximately the same size on the screen as it was on paper, provided that:
Besides numerical zoom, four more zoom types are recognized:
Zoom |
Description |
Fit Width |
Scales the image to fit the width of the window. Note: The default behavior is to select one of the fast zoom factors. As a result, the page will not fit the window's width precisely. Deselect "Favor fast magnifications for "Fit" resolutions" in the Preferences to disable this behavior. |
Fit Page |
Scales the image to fit the window. Note: The default behavior is to select one of the fast zoom factors. As a result, the page will not fit the window precisely. Deselect "Favor fast magnifications for "Fit" resolutions" in the Preferences to disable this behavior. |
One-to-One |
The image is scaled to display in pixel-to-pixel mode. In this mode, every pixel of the original image corresponds to one pixel on the screen. This is different from 100% zoom where the image is scaled so that its physical dimensions on the screen are about the same as the dimensions of the original. |
Stretch |
The image is stretched to fit the window precisely. The original proportions (aspect ratio) are ignored. |
In order to change the zoom factor, you can select the Zoom item from the pop-up menu. If the toolbar at the bottom of the window is enabled, you can select the Zoom directly there. Type the zoom factor you want and hit Enter. This is the fastest known way to set any custom zoom from 5% to 999%. You can select One-to-One, Fit Width, Fit Page or Stretch zoom by clicking on the arrow on the right side of the toolbar.
There are also keyboard shortcuts available that directly set the zoom factor.
If you view a multipage DjVu document you will need a way to navigate through it page by page. There are three ways to navigate DjVu document:
Keyboard shortcuts are the most useful way to look through a document page by page. The following hot keys are enabled:
Key |
Action |
Page Down, Page Up |
Brings you to the end or beginning of the current page. If you are already at the beginning or end of the current page, these keys will move to the next or previous page. |
Space |
Brings you to the next page. Unlike the Page Down key, it will not go to the bottom of the current page first. It will move to the next page immediately. |
Backspace |
Move to the previous page. |
Home |
Move to the beginning of the document. |
End |
Move to the end of the document. |
The above table only contains the keyboard shortcuts for navigation. Here is a complete list of keyboard shortcuts.
You can also navigate through a multipage DjVu document using the Pop-up Toolbar.
There are six buttons from the toolbar allowing you to navigate the previous page, next page, plus/minus 10 pages, the beginning and end of the document. In addition, you can select the page you want to see from the tool bar directly. These multipage navigation items will not be visible on the toolbar if the plug-in is displaying a single page document.
Please see the Pop-up Toolbar section for more details.
Using the pop-up menu, you can choose an item to Navigate. The following choices are available: Next Page, Previous Page, +10 Pages, -10 Pages, First Page, Last Page and Goto Page. When you select Goto Page, you will get a Goto Page dialog box where allowing you to specify what page you want to view.
The options available for saving a document are:
The Save icon on the popup toolbar saves the whole document.
This option is used to save your document into a single file or multiple files on your system.
This capability is useful if you already have several DjVu documents in one of the obsolete formats (See Multipage formats section). Since the plug-in understands any of the four formats (two obsolete and two current) and can save documents in any of the current formats, it is a convenient tool to do the conversion.
In order to save a multipage document, choose the menu item Save Document As from the popup menu. The document format selection dialog will appear. Choose the INDIRECT format if you want every page to be saved to a separate file (ideal for Web browsing). Choose the BUNDLED format if you want everything to go into a single file (a good format for archiving or sending via e-mail).
In the next window, enter the document filename. For BUNDLED documents, this will be the name of the bundle file. For INDIRECT documents, this will be the name of the top-level file containing pointers to page files (see Multipage formats for details). The page files will be created in the same directory as the top-level file. Their names are built-in the document.
Besides saving the whole document, you can also extract and save just one (current) page. To do this, choose the menu item Save Page As from the popup menu.
A thumbnail is a miniaturized version of an image. Thumbnails are useful because they allow users to preview large images quickly and control which ones they want to download. This version of the DjVu plug-in supports thumbnails. It can display a list of small icons (one for every page) in the left part of the window.
The DjVu 3.2 document format allows you to generate thumbnails and embed them into the document. If you do this, the plug-in can display thumbnails for every page immediately.
If you decide not to generate thumbnails, the DjVu viewer and the DjVu plug-in can still generate thumbnails on the fly. You can disable the thumbnail option by checking the Fast thumbnails checkbox in the preferences dialog. In the fast mode image thumbnails are displayed only for pages that are already decoded. The viewer will not try to decode any other page simply to display the thumbnails.
You can turn on Thumbnails by choosing Show Thumbnails from the pop-up menu or by specifying an embed flag. Thumbnails are never displayed for single page DjVu documents.
You can customize your thumbnails, allowing you to specify where they appear. To do this, choose Show thumbnails item from the popup menu. A set of icons will be displayed along the left part of the window. You can resize that part, if you feel that it is either too small or takes too much space. You can also move the thumbnails to Right, Top, Bottom or Left of the DjVu image window. Do this by clicking the right mouse button on thumbnails, and choosing appropriate option from the menu. Not all icons contain images. This is because the document probably does not have embedded thumbnails, and the default thumbnail mode is fast mode. As a result, the plug-in displays thumbnails only for those pages that have already been decoded and cached.
You can also generate thumbnails for every page. The Fast thumbnails check box in the preferences dialog is on by default. If you clear the Fast thumbnails checkbox, you will disable the fast mode and will allow the plug-in to generate thumbnails for every page.
The 3.2 release of DjVu supports a text chunk (TXTz) that can be generated by an OCR (Optical Character Recognition) engine. If you are browsing a document that has this chunk, you can search it for a specific word or combination of words (string).
To search for a string, choose Find item from the pop-up menu. The Find dialog will appear. Another way to display this dialog is to press the F.
A DjVu document may contain no textual information (simply because nobody ran an OCR engine on it). To be certain that there are no TXTz chunks in the whole document, it is necessary to load and decode every page. To search the document for TXTz chunks without decoding every page, the Search dialog always available. The dialog will indicate if there are no TXTz chunks in your document. DjVu relies on the OCR engine to generate correct textual information and zones containing separate words and lines. If the OCR engine failed when creating the textual chunk for this document, the Search may generate abnormal results.
The Copy to Clipboard option in the DjVu pop-up menu is enabled only under Windows NT operating system. This option allowes you to copy the currently displayed DjVu image in the Browser window to the Windows Clipboard. After copying, you may paste the image from the Windows Clipboard into any application that will accept input from the Windows Clipboard, or you may view the copied image with the Clipboard Viewer application. Note your display mode setting before you invoke the copy operation, since only the currently displayed image layers are copied to the clipboard.
Before copying the image from the DjVu to the Windows Clipboard, a copy of the current image is converted to the 24-bit color BMP format. This conversion is very memory intensive and may take a long time to complete on systems with a modest amount of RAM memory (i.e. those with less than 128 MB), and a modest amount of virtual memory (less than 512 MB on disk). If the copy action does not complete due to insufficient memory, try closing some other applications to free up RAM memory, or try increasing virtual memory, and issue the Copy Image to Clipboard action again. The Copy Image to Clipboard action does not modify the currently displayed image. Any graphics associated with hyperlinks embedded in the image are copied, but the hyperlink function is not copied to the Windows Clipboard.
The Export to File option in the DjVu pop-up menu enables you to save a DjVu Image in a different format on local disk. The default image format of your operating system is used to export a DjVu image. For Windows, the BMP format is the default image and for MAC OS, the PICT format is the default image.
When you select the Print option from the DjVu pop-up menu, a Print dialog box is displayed with the following options:
These options enable the selection of a printer from a list of known printers. Printing to a file is also possible by selecting the Print to file check box in the Print dialog box. A Properties submenu allows further specification of the paper size, print orientation, page layout, printing resolution, image scaling, mirror image, negative printing, and double-sided printing.
All Pages - Prints all pages of a single or a multi-page DjVu document.
Pages - Enables printing of a specified range of pages from a multi-page document.
Selection - If this check box is selected, the DjVu plug-in prints only the region of the DjVu page that is being displayed in the plug-in window. This option enables you to print a selected region of the page. This is useful for printing large images.
Regular - If this radio button is checked, the plug-in prints at document resolution.
Reduce to Fit - This radio button enables the DjVu plug-In to set the optimum resolution so that the image fits completely onto the printed page.
Current Zoom - If this radio button is checked, the plug-in prints the DjVu image at the current zoom factor, which is set to view the image on screen.
Sets the number of copies of each page printed. The default number of copies to print for each page is one.
Black & White - Prints the foreground layer in black and white, sending the information to the printer using the highest resolution available in memory. This ensures maximum readability.
Color - The resolution and the quality of color printing is controlled by the various settings in the Preferences dialog box.
NOTE: The DjVu plug-In does NOT use the Print command that is found on the main browser menu bar to print DjVu images. Instead, to print a loaded DjVu image, select the Print option from the DjVu popup Menu, or click on the print icon on the DjVu popup toolbar.
This dialog box contains information about the currently displayed page, including image dimensions, compression ratio, and a list of chunks (or layers) that the image is composed of. Refer to the Chunk names section for a brief description of supported chunks. Choose item Page information from the pop-up menu in order to display the Page information dialog.
The dialog box contains the name of the document, the format of the document, the total size of the document, the number of pages in the document, number of files (only for DjVu 3.0 and newer documents), and a list of all pages with names and sizes.
You can double click on any page in the page list to go to a specific page.
For DjVu 3.2 documents, the dialog shows a Thumbnails tab, displaying information about integrated thumbnail files if any. The All Files tab shows a list of all files in the document including thumbnail files and directory files.
When running the DjVu Web Browser Plug-in for the first time, you may want to customize some of the settings. To do so, click the Preferences button in the Welcome to DjVu dialog box. The Preferences dialog box appears with several settings that you can adjust. The table below describes each of these settings.
Setting |
Description |
Display & Printer preferences |
Here you can adjust the gamma correction for your monitor. Drag the slider until all four squares look approximately the same. |
Magnifying glass preferences |
These settings are related to the magnifying glass. The plug-in can display a magnifying glass to closely observe the details of a portion of image. See Magnifying Glass for more details. Size is the size of the magnifying glass, which is displayed as a square of the given size. Zoom is the zoom factor used to magnify the image portion viewed with magnifying glass. |
Hyperlink
Preferences:
|
On slow machines displaying hyperlinks may take some precious resources and slow things down. To prevent this from happening you can check the "Draw using simple border". Once it is checked, all hyperlinks will be drawn using the XOR method directly into the window. This will be fast but not pretty. In addition, sometimes you may want to see all hyperlinks on a given page. To do this, you can press a magic key (press and keep it pressed for some time), which is customizable in the "Show all hyperlinks" keys tool bar. The default magic key is SHIFT. |
Cache preferences |
The DjVu plug-in uses cache to store decoded pages in memory. This preference setting allows you to set the size of the cache. Please note that a page can be decoded, but not rendered. "Decoding" is the first stage of page preparation. After a page has been decoded, it is still stored in a somewhat compressed state in memory until it is rendered for displaying on the screen. The Decoded pages cache is automatically turned off for files with no .djvu or .djv extension. Web developers can turn this cache on or off using either EMBED flags or CGI arguments. The Clear Cache button clears all cached documents from the cache. |
Toolbar preferences |
You can customize the pop-up toolbar displayed at the bottom of the DjVu plug-in's window. You can disable pop-up toolbar completely, or it will only show when the mouse is on top of or near it. Note that the toolbar is never displayed in small EMBED windows if more than half of it would not be visible. |
Zoom preferences |
Favor fast zooming for "Fit" resolutions setting tells the plug-in how to scale image in "Fit Width" and "Fit Page" resolutions. The internal rendering code is the fastest at magnifications represented by integer numbers. On fast machines you won't notice the difference, but on slower machines you may want to check this checkbox in order to gain some speed. When it is checked (default) the plug-in will find the closest integer magnification and display the image so that it still fits (width or page), but not necessarily precisely. If this is checked, the plug-in selects optimal resolutions while you ZoomIn or ZoomOut. |
Thumbnails preferences |
If Fast Thumbnails is checked, the plug-in will display the thumbnail image only for those pages for which the image is available. It will not try to download the page and prepare thumbnail; it will display a default image for those pages. Please see thumbnails for more information. If Smart Thumbnails is checked, the plug-in will download and display all visible thumbnails on screen first and then download the remaining. This can be combined with Fast Thumbnails to ensure only visible thumbnails are downloaded and displayed. |
Save preferences |
Unless checked, all changes in the preferences will affect only the currently loaded instance of the plug-in. If you want to save changes to disk, make sure that this check box is checked. |
The DjVu Plug-in displays a magnifying glass to look closer into the details of a DjVu image by pressing and holding SHIFT/CTRL key. The exact key depends on your selection of "Show All Hyperlinks Key" in the DjVu Preferences Dialog. The plugin will take the other key which is not assigned for "Show All Hyperlinks" from CTRL and SHIFT. You can move the magnifying glass around with mouse, and also pan the image while this feature is on.