LEAD's JBIG filter defines a method for lossless compression encoding of a bi-level image (two-color image). This method can also be used for coding grayscale and color images. LEADTOOLS completely supports all three types of images, giving you the ability to make full use of this powerful compression technology. LEADTOOLS also supports the progressive capability of JBIG, allowing you to store and send multiple representations of images at different resolutions without any extra storage overhead.
JBIG is an acronym for 'Joint Bi-level Image experts Group'. This was a group of experts nominated by national standards bodies and major companies to work to produce standards for bi-level image coding.
The JBIG group has developed IS 11544 (ITU-T T.82) standard for the lossless compression of a bi-level image. It can also be used for coding grayscale and color images with limited numbers of bits per pixel. It is similar to Group 3 or Group 4 Fax, offering between 20% and 80% improvement in compression over these methods. JBIG compression averages about a 20:1 over the original uncompressed image.
LEADTOOLS completely supports all three types of images (bitonal, grayscale and color), giving you the ability to make full use of this powerful compression technology. LEADTOOLS also supports the progressive capability of JBIG, allowing you to store and send multiple representations of images at different resolutions without any extra storage overhead.
To achieve the highest compression ratios available in the JBIG format, LEADTOOLS takes full advantage of all the functional blocks of this robust standard:
The Adaptive Arithmetic Encoder, which presents the heart of this format, has the ability to predict and hence encode future data symbols based on the data which is being currently encoded.
The Adaptive Template Block provides real coding gain for images rendered by grayscale with halftoning. This gain ratio approaches 80% in some situations.
The Typical Prediction Block speeds implementations and provides some coding gain.
The Resolution Reduction Block is used to get a lower resolution version of an image so that no loss of data is encountered. This is mainly important for bi-level images, to avoid any deletion of thin lines.
The Deterministic Prediction Block provides good coding gain when saving more than one resolution layer in the same file.
Implementing JBIG Features (API)