Support for 1000 ppi Images
The FBI has developed a standard for the compression and formatting of 1000 ppi fingerprint and palm images, called “Profile for 1000 ppi Fingerprint Compression”. This profile requires the use of JPEG2000 for compression and formatting of 1000 ppi images. WSQ will continue to be used for 500 ppi images. Like WSQ, JPEG2000 uses a wavelet-based compression algorithm that performs particularly well for large images. It is an established ISO standard, used extensively for medical imaging and digital archiving applications.
The FBI’s IAFIS and all legacy AFIS systems will continue to require 500 ppi WSQ compressed data. To address this requirement, WSQ1000 enables efficient transcoding from 1000 ppi JPEG2000 images to 500 ppi WSQ images.
The JPEG2000 standards are complex, with many variable settings intended to help optimize its use for different applications. The FBI 1000 ppi Profile includes several mandatory encoding parameters to ensure the optimization of JPEG2000 for 1000 ppi fingerprint images.
Features of WSQ1000
WSQ1000 is a combined library that includes Aware FBI-compliant WSQ and Aware FBI-compliant JPEG2000. Aware’s WSQ1000 software toolkit provides libraries with all the functionality required to build a 1000 ppi workstation fully compliant with this new specification.
It includes JPEG2000 compression and formatting in strict compliance to the FBI profile, as well as standard-compliant WSQ compression software.
Aware’s WSQ and JPEG2000 are fully compliant with the FBI standards. Additionally, Aware JPEG2000 is compliant with the ISO compliance for JPEG2000. The code is optimized for speed and data precision. Computationally intensive parts of the encoder and decoder blocks are coded in assembly language and specialized Intel or AMD multimedia instruction sets.
Ease of use
Designed specifically for vendors and agencies that must build systems to acquire, manage, display, and exchange FBI-compliant fingerprint images, WSQ1000 can be easily and efficiently incorporated into existing applications and systems.
The WSQ1000 toolkit provides example programs with source code and project files, and clear, concise documentation.
Multiple Compression Methods
The FBI WSQ guidelines for the compression of ten-print data remains the same: select a “Q factor” such that the average achieved ratio of all 14 ten-print images is 15:1. Like traditional JPEG, the WSQ Q factor parameter specifies a quality value. The same Q factor will yield slightly different ratios for different images. The different ratios are primarily a factor of the percentage of white space in a fingerprint image. Those images with more white space are more compressible.
Certain non-ten-print applications, however, may benefit from an accurate rate-control method that provides compression to an exact ratio or exact file size. WSQ1000 includes a separate function that provides the ability to target compression ratio, file size, or bit rate (bits/pixel) to within 1% of the specified value. This capability is useful for memory constrained devices such as smart cards that include pre-allocated memory blocks for fingerprint images.
File I/O
WSQ1000 incorporates an object-based design that supports multiple different file conversions. As shown in the diagram below, the object can accept several file types as input. Compression, decompression and output file type are specified as parameters to the object. The resulting codestream and file format are output based on the parameter settings.
Progressive Decompression
A key feature of WSQ1000 is its ability to decompress fingerprint images to resolutions that are a fraction of the original size, without decompressing to the full resolution and then down sampling. This is useful in computer displays of ten-print cards. Each compressed fingerprint image can be decompressed to 1/4 or 1/16 of the original size so that a full ten-print card can be quickly and elegantly displayed within the user interface of an application, without unnecessary delay or usage of CPU cycles.
WSQ/JP2 File Information Logging Function
This function allows retrieval of key information from a WSQ or JP2 file without decompression. It allows a system to rapidly log information about the files at key points within the workflow. This features helps to detect and isolate corrupt or overly-compressed files and, in general, provides a mission critical quality assurance resource.
Comment Insertion/Extraction
This feature enables rapid insertion of arbitrary text strings into a WSQ or JP2 file in compliance with both standards. Custom text strings or security codes can be embedded directly in the file to act as a redundant file identification tool. In addition, information which is essential to a particular system can be carried directly in the WSQ or JP2 file as a comment, without the added complexity of creating new data entry functions or files.
Full-Error Code Return Conditions
To signal run-time errors such as inconsistent input parameters, null pointers and corrupt bitstreams, WSQ1000 returns a full suite of error codes from both the compression and decompression library. These codes provide an application layer feature to detect problems and suggest solutions to correct the run-time errors.
Re-entrant & Thread Safe
WSQ1000 is a single-threaded library, configured to operate efficiently and safely in multi-threaded applications. This feature enables system developers to design complex applications capable of performing a variety of tasks simultaneously.
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