Block histogram

SourceAFIS » Algorithm » Transparency » Block histogram

Histogram, a part of algorithm transparency, contains pixel value histogram for every primary block. Pixels are taken from scaled image. It is computed during feature extraction. Histogram is processed into smoothed histogram before it is used to compute contrast.

KeyMIMEFilename in ZIP


Histogram visualization can be created from this stage's binary data mapped onto blocks. Original fingerprint image is in the background. Visualization itself is not part of transparency data.

Array of histograms, one per block
Histogram is shown separately for every primary block on the image. Vertical axis of histograms is logarithmic.


Histogram is a 3-dimensional array (or cube) of integers. Two dimensions correspond to X and Y positions of primary blocks. Every block has its own histogram consisting of bins that represent shades of gray from white (0) to black (255). Bins are the third dimension of the histogram cube. Histogram is encoded in CBOR:

Example: 005-histogram.cbor

  "width": 26,
  "height": 25,
  "bins": 256,
  "counts": [
    "... skipped 166,396 items in range 0 to 225 ...",