Fingerprint Image Compression Certified by FBI WSQ Specification, Version 3.1

It has been nearly impractical to use the SFM series in sending fingerprint images, as it provides only UART serial communication, which supplies a stable network speed of 115,200 bps. For this reason, when sending a fingerprint image from SFM to Host PC, users used to quantize from the original format to 4-bit gray or binary format, which resulted in an image quality that is significantly compromised. (Figure 1)

The SFM5500 series overcame this problem and have been equipped with the new technology to compress fingerprint images and quickly send high quality images via a low bandwidth network environment. When compressing, the quality degradation is minimized (Figure 2), but the data size is lowered by 90%, reducing the time it takes to be sent by 90%, as well. Moreover, you can set the system to compress images in different levels, enabling you to appropriately adjust the transfer speed and the image quality according to its use (Figure 3).

Moreover, starting with SFM SDK v1.6, it offers the WSQ decoding function, enabling the original recovery of the WSQ compression image sent by SFM. The WSQ image compression is an image compression method based on the wavelet transform (Figure 4), optimal for fingerprint images; and its strength is that it retains the image quality much better than block-based compression methods, such as JPEG. (Figure 5)

The image compression technology applied to SFM5500 is a standard WSQ image compression technology of NIST and has been certified by NIST and the FBI. Therefore, any WSQ compression stream sent from SFM is restorable using any viewer with an FBI-certified decoder.