Filtered mask

SourceAFIS » Algorithm » Transparency » Filtered mask

Filtered mask, a part of algorithm transparency, refines combined mask using a set of filters into a mask marking valid fingerprint area. It is computed during feature extraction. It is used to derive equalized image, block orientation and smoothed orientation, parallel smoothing and orthogonal smoothing, and binarized image and derived data. It is later processed into pixel mask and subsequently into inner mask.

Key	MIME	Filename in ZIP
`filtered-mask`	`application/cbor`	`011-filtered-mask.cbor`

Visualization

Mask visualization can be computed from this stage's binary data mapped onto blocks and the original fingerprint image. Visualization itself is not part of transparency data.

Valid fingerprint area highlighted yellow on fingerprint image — Filtered contrast mask. Yellow color marks valid fingerprint area.

Format

Filtered mask has the same format as absolute contrast mask except that true marks high-contrast (interior) blocks while false marks low-contrast (exterior) blocks.

Example: 011-filtered-mask.cbor

{
  "width": 26,
  "height": 25,
  "cells": [
    false,
    false,
    "... skipped 646 items ...",
    false,
    false
  ]
}