Absolute contrast mask

Absolute contrast mask, a part of algorithm transparency, is a set of primary blocks on the block map where contrast falls below some fixed threshold. It is computed during feature extraction. Absolute contrast mask contributes to combined mask.



Absolute contrast visualization can be computed from this stage's binary data combined with block map and original fingerprint image. Visualization itself is not part of transparency data.

Absolute contrast mask visualized as yellow masked out area around fingerprint image
Absolute contrast mask. Yellow area consists of blocks excluded due to low contrast.

Binary data

Binary data is a 2D array with dimensions that can be found in the associated json data, height first, and that are also equal to the number of primary blocks in the block map. Binary data consists of rows of primary blocks ordered from top to bottom. Every row is a sequence of blocks from left to right. Every block is a single byte with value 0 (high contrast) or 1 (low contrast).

Example: 013-absolute-contrast-mask.dat


Json data describes basic properties of the binary data, most importantly dimensions of the mask, which is the same as the number of primary blocks.

Example: 012-absolute-contrast-mask.json

  "axes": [
  "dimensions": [
  "scalar": "boolean",
  "bitness": 8,
  "format": "false as 0, true as 1"