| CSEPDJVU(1) | DjVuLibre-3.5 | CSEPDJVU(1) |
csepdjvu - DjVu encoder for separated data files.
csepdjvu [options] [sepfiles]... outputdjvufile
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.
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 setting that ensures the color uniformity.
Each separated data file contains a concatenation of one or more separated 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:
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.
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 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 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.
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 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 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 represented 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 number, 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.
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 decimal 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.
Each page is followed by an arbitrary number of comment lines starting with character "#" and terminated by a linefeed character. Certain comment lines have special meanings. In the following constructs, all the strings are UTF-8 encoded and represent in the style of Postscript strings, that is, surrounded with parenthesis and using C-style escape sequences introduced by a backslash.
This program was initially written by Léon Bottou <leonb@users.sourceforge.net> and was improved by Bill Riemers <docbill@sourceforge.net> and many others.
| 10/11/2001 | DjVuLibre-3.5 |