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US Navy
Magazine Compared in PDF, DjVuRaster and DjVuDigital
formats
A review by
James Rile, PlanetDjVu, May 25, 2002 The
U.S. Navy publishes a monthly magazine called "All Hands". It
is available on-line at: http://www.chinfo.navy.mil/navpalib/allhands/ah-top.html From
1997 through 2001 the magazine was reformatted in HTML for on-line
viewing. Starting in 2002, the magazine is offered in
PDF format. The PDF magazine issues appear to be the same
prepress PDF files used to create the printed version of the
magazine, but downsampled for web delivery.
While we applaud the retention of the original print layout
for web delivery, which is possible with PDF but not possible with
HTML, we see a problem with the file size. A more effective
format for web delivery of this magazine would be in the DjVu file
format. There are two methods available for the conversion of PDF
files to DjVu files. We will call them DjVuRaster and DjVuDigital.
DjVuRaster first makes a single color image of the PDF page,
then segments this image into background and foreground layers.
It addition to putting text into the foreground layer, this
also puts high-contrast regions of the photos into the foreground
layer. DjVuDigital segments the PDF page into background and
foreground layers, and does this by analysizing the objects of the
PDF page to determine if they should go into the background or
foreground layers. With this method, photos go entirely to the
background layer. This increased file size slightly , but the
page quality is better. When
you look at the DjVuRaster and the DjVuDigital examples, use the
Mode buttons in the DjVu plugin to see how it was
segmented. When
you compare the performance of either DjVu version to the PDF
version, you will see the performance and quality of the DjVu files
make them attractive alternatives to the web delivery of color
magazines such as "All Hands" from the U.S.
Navy.
Note that the DjVuDigital examples were created with the
Any2DjVu conversion server sponsored by www.djvu.org. See the
home page of PlanetDjVu for a link to
Any2DjVu. October 18, 2002 - Extension to Study We
are extending this study today to show the benefits of PDF size
optimization using the CVision compression engine for PDF.
This engine analyses each graphic object in the PDF file and
then applies optimum compression to it, without unduly degrading the
quality of the graphic objects. Here are the results:
November 26, 2002 - Extension to
Study We
are extending this study today to show the benefits of PDF size
optimization using the PDF Enhancer product (SPE) from PDF Sages,
Inc. This engine analyses each graphic object in the PDF file
and then applies optimum compression to it, without unduly degrading
the quality of the graphic objects. Here are the results:
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