ImageGear Professional DLL v17.1 for Windows Accusoft
JBIG2
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ImageGear Professional DLL v17.1 for Windows > User Guide > File Format Reference > ImageGear Supported File Formats Reference > JBIG2

Glossary Item Box

Full Name JBIG2 (bilevel image compression)
Format ID IG_FORMAT_JB2 = 62
File Extension(s) *.jb2
Data Type Raster Image
Data Encoding Binary
ImageGear Multipage Support Yes
ImageGear Alpha Channel Support No
ImageGear Platforms Support WIN32

To support the JBIG 2 format, attach the ImageGear JBIG2 Component to Core ImageGear.

ImageGear Supported Versions:

N/A

ImageGear Supported Features:

ImageGear Read Support:

IG_COMPRESSION_JBIG2 - Indexed RGB: 1 bpp

ImageGear Write Support:

IG_COMPRESSION_JBIG2 - Indexed RGB: 1 bpp

ImageGear Filter Control Parameters:

Filter Control Parameter Type Default Value Available Values Description
JBIG2_DISABLE_CSM AT_BOOL FALSE TRUE, FALSE This parameter, when TRUE, specifies that Combined Symbol Matching will not be used. When this option is TRUE, the compression algorithm uses lossy compression. Using lossy compression is likely to result in an image that is smaller (lossless compression can result in encoded images up to 2-3x larger) and a compression speed that is slower than when using lossless compression.
JBIG2_FILE_ORG INT

IG_JB2_FILEORGDISTRIBUTED = 0
  • IG_JB2_FILEORGDISTRIBUTED = 0
  • IG_JB2_FILEORGCENTRAL = 1

This function specifies the file format generated by the encoder.

  • IG_JB2_FILEORGDISTRIBUTED creates a sequential document suitable for transmission.
  • IG_JB2_FILEORGCENTRAL creates a document that allows random access to the pages in the document.

JBIG2 files may be organized in two ways; by sequential access or by random access.

  • In sequential organization (IG_JB2_FILEORGDISTRIBUTED), each page's header immediately precedes the page’s data.
  • In random access organization (IG_JB2_FILEORGCENTRAL), all page headers are collected together at the beginning of the file, followed by the data for all of the segments in the same order.

The second organization permits a decoder to determine all the segment dependencies without reading the entire file. Sequential organization is suitable for transmitting images through a network  -  page by page. Random access organization is used for quick access to each page in an image.
JBIG2_GENERIC_IMAGE_MMR AT_BOOL FALSE TRUE, FALSE

This parameter specifies that MMR (G4) encoding should be used for generic image segments.

A typical JBIG2 page contains text data, i.e., small characters arranged in horizontal or vertical rows. The characters in a page’s text section are called symbols in JBIG2. A page may also contain halftone data, i.e., grayscale or color photographic images that have been dithered to produce bi-level images. A page may also contain non-text data, such as large characters, line art, and noise. Such non-text data is called generic data in JBIG2.

There are two methods for coding the generic image segment: arithmetic coding and MMR (G4) coding (MMR - Modified Modified READ). MMR provides less compression (up to 4-5 times) than image bitmap compression based on arithmetic coding. Image bitmap decoding using MMR is faster than image bitmap decoding based on arithmetic coding.  
JBIG2_GENERIC_IMAGE_TEMPLATE INT IG_JB2_GENERICIMAGETEMPLATE16 = 2
  • IG_JB2_GENERICIMAGETEMPLATE16 = 2
  • IG_JB2_GENERICIMAGETEMPLATE13 = 3
  • IG_JB2_GENERICIMAGETEMPLATE10A = 4
  • IG_JB2_GENERICIMAGETEMPLATE10B = 5
 This parameter specifies one of four templates for the arithmetic coder. The JBIG2 working draft describes these templates in detail. Typically, IG_JB2_GENERICIMAGETEMPLATE16 is used for halftone photographic images and IG_JB2_GENERICIMAGETEMPLATE10B or IG_JB2_GENERICIMAGETEMPLATE10A is used for images that contain primarily text. IG_JB2_GENERICIMAGETEMPLATE13 falls somewhere between halftone images and text.
JBIG2_REMOVE_FLY_SPECK AT_BOOL FALSE TRUE, FALSE This parameter specifies whether or not isolated single pixels, also known as “fly specks”, should be removed.

Comments:

The JBIG2 format supports multi-page images and is the most effective compression method for  bitonal (B\W) images. JBIG2 Format Filter supports some features of bitonal file processing. These features are determined by IG_FLTR_ flags. This Format Filter also allows you to save JBIG2 images with different compressions depending of image bit depth.

JBIG2 is a highly-compressed black and white image format that uses symbol recognition and substitution for very good compression results. Any black and white image can be compressed using JBIG2 including images stored as Group 4, Group 3, MO:DCA, TIFF, PDF and others.

The JBIG2 compression algorithm searches for groups of pixels arranged in similar shapes and use them to define a symbol. Rather than retaining information on the placement of each pixel, a table is created for common symbols. This allows users to see incredible reductions in file sizes. Compression rate matches 100:1 compared to uncompressed black and white TIFFs.

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