CSEPDJVU(1) DjVuLibre-3.5 CSEPDJVU(1)NAMEcsepdjvu - DjVu encoder for separated data files.
SYNOPSIScsepdjvu [options] [sepfiles]... outputdjvufile
DESCRIPTION
This program creates a DjVuDocument file outputdjvufile from separated
data files sepfiles. It can read separated data from the standard
input when given a single dash instead of the separated data file
names. This feature is intended for pre-processing programs that push
separated data into csepdjvu via a pipe.
Each separated data file represents one or more page images. When the
program arguments specify multiple pages, all the pages are encoded and
saved as a bundled multi-page document. When the program arguments
specify a single page, the page is encoded and saved as a single page
file.
OPTIONS-d n Specify the resolution information encoded into the output file
expressed in dots per inch. The resolution information encoded
in DjVu files determine how the decoder scales the image on a
particular display. Meaningful resolutions range from 25 to
6000. The default value is 300 dpi.
-q n,...,n
-q n+...+n
Specify the encoding quality of the IW44 encoded background
layer. The option argument contain several integers (one per
chunk) separated by either commas or pluses. This option is
similar to option -slice of program c44. Please refer to the
c44(1) man page for additional details. The default quality
specification is -q 72,83,93,103.
This option does not apply to uniformly white background that
were not specified by the separated data but are called for by
the DjVu specification. Such background images always come at
the lowest possible resolution and with a standard quality set‐
ting that ensures the color uniformity.
-t Program csepdjvu interprets certain comments in the separated
file to construct a hidden text layer in the DjVu file. This
layer records the location of each word for hiliting purposes.
This option reduces the file size by simply recording the loca‐
tion of each line.
-v Display a brief message describing each page.
-vv Display extensive informational messages during encoding.
SEPARATED DATA FILE FORMAT
Each separated data file contains a concatenation of one or more sepa‐
rated page images. Each page is logically represented by a foreground
image with a transparent color and by a background image visible
through the transparent pixels. The data for each separated page image
is the concatenation of the following data blocks:
* A foreground image encoded using either the "Color RLE format" or
the "Bitonal RLE format". These formats are described later in this
section.
* An optional background image encoded as a "Portable Pixmap" ( PPM ).
This well known format is summarized later in this section. The
absence of a background image simply indicates that a uniformly
white background should be assumed.
* An arbitrary number of comment lines starting with character "#" and
terminated by a linefeed character. Comment lines whose first word
starts with a capital letter have special meanings documented later
in this document.
The dimensions (width and height) of the background image must be
obtained by rounding up the quotient of the foreground image dimensions
by an integer reduction factor ranging from 1 to 12. Assume, for
instance, that the width of the foreground is 2507 and the reduction
factor is 3. The width of the background image will be the integer
ratio (2507+2)/3.
Color RLE format
The Color RLE format is a simple run-length encoding scheme for color
images with a limited number of distinct colors. The data always begin
with a text header composed of the two characters "R6", the number of
columns, the number of rows, and the number of color palette entries.
All numbers are expressed in decimal ASCII. These four items are sepa‐
rated by blank characters (space, tab, carriage return, or linefeed) or
by comment lines introduced by character "#". The last number is fol‐
lowed by exactly one character which usually is a linefeed character.
The header is followed by the color palette containing three bytes per
color entry. The bytes represent the red, green, and blue components
of the color.
The palette is followed by a collection of four bytes integers (most
significant bit first) representing runs of pixels with an identical
color. The twelve upper bits of this integer indicate the index of the
run color in the palette entry. The twenty lower bits of the integer
indicate the run length. Color indices greater than 0xff0 are
reserved. Color index 0xfff is used for transparent runs. Each row is
represented by a sequence of runs whose lengths add up to the image
width. Rows are encoded starting with the top row and progressing
toward the bottom row.
Bitonal RLE format
The Bitonal RLE format is a simple run-length encoding scheme for
bitonal images. The data always begin with a text header composed of
the two characters "R4", the number of columns, and the number of rows.
All numbers are expressed in decimal ASCII. These three items are sep‐
arated by blank characters (space, tab, carriage return, or linefeed)
or by comment lines introduced by character "#". The last number is
followed by exactly one character which usually is a linefeed charac‐
ter.
The rest of the file encodes a sequence of numbers representing the
lengths of alternating runs of transparent and black pixels. Lines are
encoded starting with the top line and progressing toward the bottom
line. Each line starts with a white run. The decoder knows that a line
is finished when the sum of the run lengths for that line is equal to
the number of columns in the image. Numbers in range 0 to 191 are rep‐
resented by a single byte in range 0x00 to 0xbf. Numbers in range 192
to 16383 are represented by a two byte sequence: the first byte, in
range 0xc0 to 0xff, encodes the six most significant bits of the num‐
ber, the second byte encodes the remaining eight bits of the number.
This scheme allows for runs of length zero, which are useful when a
line starts with a black pixel, and when a very long run (whose length
exceeds 16383) must be split into smaller runs.
Portable Pixmap (PPM) format
The Portable Pixmap format is a well known format for representing
color images. Check the ppm(1) man page for complete information.
The data always begin with a text header composed of the two characters
"P6", the number of columns, the number of rows, and the maximal value
of a color component (usually 255). All numbers are expressed in deci‐
mal ASCII. These three items are separated by blank characters (space,
tab, carriage return, or linefeed) or by comment lines introduced by
character "#". The last number is followed by exactly one character
which usually is a linefeed character.
The rest of the file encodes all the pixels. Each pixel is represented
by three bytes representing the red, green and blue component of the
pixel. Pixels are ordered in left to right, top to bottom.
Comments in separated files
Each page is followed by an arbitrary number of comment lines starting
with character "#" and terminated by a linefeed character. Comment
lines whose first word starts with a capital letter have special mean‐
ings. The following constructs are currently defined:
* # T px:py dx:dy wxh+x+y (string)
This constructs indicates that the piece of text string must be
associated with an area of size wxh at position x,y relative to the
lower left corner of the page. The string is UTF-8 encoded. Special
characters can be escaped as in PostScript using the backslash char‐
acter. Integers px, and py represent the position of the current
point on the text baseline before the text was drawn. The drawing
operation then moves the current point by dx, and dy pixels. When
such comments are present, csepdjvu produces a hidden text layer for
the corresponding pages.
* # L wxh+x+y (url)
This construct indicates that an hyperlink to url url should be
associated with area of size wxh at position x,y. When such com‐
ments are present, csepdjvu produces pages with an annotation chunk
containing the specified hyperlinks.
* # B count (string) (#pageno)
This constructs provides outline information for the document. An
outline entry entitled string is associated with page pageno. Inte‐
ger count indicates how many of the following outline entries must
be attached to the current entry as subentries. When such comments
are present in the first page csepdjvu produces an navigation chunk
with the specified outline.
CREDITS
This program was initially written by Léon Bottou <leonb@users.source‐
forge.net> and was improved by Bill Riemers <docbill@sourceforge.net>
and many others.
SEE ALSOdjvu(1), ppm(5), c44(1)DjVuLibre-3.5 10/11/2001 CSEPDJVU(1)
