Past work · compression

Media security and data formats

Two papers on how far a finger-vein image can be compressed before recognition starts to fail.

Abstracts are quoted verbatim from the papers. Venues, authors, page numbers and DOIs were verified against the University of Salzburg repository and dblp. The workflow diagrams were drawn for this page, neither paper contains a pipeline figure, so each diagram follows the method its paper describes and is labelled as such below.

Finger Vein Image Compression with Uniform Background

ACM ICBEA 2019 · Stockholm · pp. 23-27 · Sole first author · WaveLab, University of Salzburg

Finger-vein image SDUMLA-HMT · UTFVP Replace background with uniform grey (0.1) Smooth the edge THE CRITICAL STEP LOSSLESS · 6 CODECS ≈2× smaller PNG 45 → 25 KB LOSSY → MC / SIFT holds to ratio ≈40 recognition measured as EER Skip the smoothing and the new sharp boundary creates compression artifacts that make recognition worse, not better. That is the paper’s central caution.

Workflow drawn from the method described in the paper. Not a figure from the paper.

Abstract, verbatim

We propose to replace the background data in finger vein imagery by uniform gray data and implications on (i) achieved lossless compression performance and (ii) obtained recognition accuracy in case of lossy compression are determined employing 2 public datasets. Results indicate that replacement of original background by uniform one is definitely profitable for lossless compression, while the lossy case with impact on recognition accuracy has to be handled with caution as introduced sharp edges between finger area and background lead to artifacts which in turn degrade recognition performance. After having smoothed those areas, recognition performance is improved when replacing background for all settings.

≈2×smaller lossless files: PNG 45 → 25 KB, JPEG-LS 298 → 168 KB
ratio 40how far the lossy gains hold before recognition suffers
2 datasetsSDUMLA-HMT and UTFVP, both public

What it does. Segment the finger from the background, paint the background a single flat grey, then smooth the boundary that this creates. Evaluate twice: six lossless codecs for file size, and the lossy codec set followed by Maximum Curvature and SIFT recognition for accuracy.

The change, on real samples

Original (UTFVP)
Original (UTFVP)
Background replaced with uniform grey (UTFVP)
Background replaced with uniform grey (UTFVP)
Original (SDUMLA-HMT)
Original (SDUMLA-HMT)
Background replaced with uniform grey (SDUMLA-HMT)
Background replaced with uniform grey (SDUMLA-HMT)

Recognition under compression

Maximum Curvature on UTFVP, JPEG 2000
Maximum Curvature on UTFVP, JPEG 2000
SIFT on SDUMLA-HMT, JPEG 2000
SIFT on SDUMLA-HMT, JPEG 2000
The limit the paper itself states

The gain depends on how much background a dataset has. Both datasets here have similar background fractions, so the ≈2× figure may not transfer to a dataset framed differently.

Funded by the Austrian Science Fund (FWF), grant 27776.

BibTeX
@inproceedings{maser2019icbea,
  author    = {Maser, B. and H{\"a}mmerle-Uhl, Jutta and Lipowski, Tamara and Uhl, Andreas},
  title     = {Finger Vein Image Compression with Uniform Background},
  booktitle = {Proc. 3rd Int. Conf. on Biometric Engineering and Applications (ICBEA)},
  pages     = {23--27},
  year      = {2019},
  doi       = {10.1145/3345336.3345347}
}

Finger-vein Sample Compression in Presence of Pre-Compressed Gallery Data

BIOSIG 2018 · Darmstadt · pp. 1-5 · Second author · Media Data Formats Lab, University of Salzburg

GALLERY · STORED YEARS EARLIER Gallery images ENROLLED Already compressed JPEG or JPEG 2000, ratio 10 or 30 PROBE · CAPTURED NOW New sample TO VERIFY Compressed how? JPEG · JPEG 2000 +3 ROI · JPEG-XR · BPG Matching Maximum Curvature · SIFT MEASURED AS Equal Error Rate The question is not how to compress, but how to compress a new sample when the gallery it must match was compressed with older technology at a different ratio.

Workflow drawn from the method described in the paper. Not a figure from the paper.

Abstract, verbatim

Compression settings for sample (probe) finger vein data in case of already pre-compressed gallery data are investigated. Inhomogeneous compression scenarios are assessed where probe data can be compressed with different compression technique and compression ratio compared to gallery data using 4 lossy compression schemes, 2 finger vein recognition schemes, and 2 data sets. Results obtained indicate that in case of JPEG2000 pre-compressed gallery, also sample images should be compressed in the same manner, while for JPEG pre-compressed gallery, the optimal sample compression setting depends on the dataset, on the target compression ratio, and on the recognition scheme employed.

ratio 30JPEG holds only this far; past it error rates rise sharply
0.14largest EER gap observed between compression settings
match itwith a JPEG 2000 gallery, compress the probe the same way

What it does. Compress the gallery the way it would have been years ago, compress a fresh probe every other way, match them with two recognition schemes, and see which probe setting survives. The answer is clean for a JPEG 2000 gallery and messy for a JPEG one: there it depends on the dataset, the target ratio, and the recognition scheme.

Results

Maximum Curvature on UTFVP, JPEG 2000 gallery, with JPEG, and without
Maximum Curvature on UTFVP, JPEG 2000 gallery, with JPEG, and without
SIFT on UTFVP, JPEG gallery at ratio 10 and ratio 30
SIFT on UTFVP, JPEG gallery at ratio 10 and ratio 30

The grey line climbing off the top of both charts is JPEG. It tracks the others to about ratio 30, then the error rate explodes.

BibTeX
@inproceedings{lipowski2018biosig,
  author    = {Lipowski, Tamara and Maser, B. and H{\"a}mmerle-Uhl, Jutta and Uhl, Andreas},
  title     = {Finger-vein Sample Compression in Presence of Pre-Compressed Gallery Data},
  booktitle = {Proc. Int. Conf. of the Biometrics Special Interest Group (BIOSIG)},
  pages     = {1--5},
  year      = {2018},
  doi       = {10.23919/BIOSIG.2018.8553484}
}