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A Technical Comparison between PDF and DJVU

2008-01-15 21:27 246 查看
Item
PDF
DJVU
Description of Layout
Driven by (a subset of) PostScript
Structure (brief)
object based, offset of indirect objects
described with device independent Cartesian coordinate system
Characters
Font-based
Rendering characters as images
Imaging Features
described with device independent Cartesian coordinate system, named graphical elements
Vector Graphics
Constructed with Paths, as defined in PostScript, with various patterns
Not mentioned
Likely not supported
Raster Images
(coding techniques)
1. ASCII Coding
(somewhat deprecated)
2. Run-length coding
3. Dictionary coding, LZW, FLATE, …
4. Built-in compressor with prevailing image compression standards: JPEG; JBIG(PDF1.4); JPEG2000(PDF 1.5)
1. 3-level text-background
separation, specified IW44
wavelet compression for
background and foreground, JB2 for bi-level mask image, which takes advantage of the similarity between shapes on the page, e.g.
nearly-identicalness of literal symbols of same character and font.
2. Arithmetic coding
3. Progressive loading
OCR
Supported
Supported
Advantage
Vector graphics
Scanned (raster) images
/ documents
high quality and high
compression rate
Conclusion
One of the most popular and practicable way of presenting book in computer
Excellent compression method for text-based image sequences
Supported elements
[All those supported by DJVU]
Sound
Interactive forms
Javascript programs
Table
Hyper link
Meta-data
DRM
Supported
Not specified
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