Decoded image

Decoded image, a part of algorithm transparency, is the original fingerprint image used for feature extraction (template construction). Decoded image contains unchanged pixels as deserialized by SourceAFIS except that pixel values are mapped to floating-point range between 0 and 1. It is an input to image scaling.

KeywordSuffixZip
decoded-image.json001-decoded-image.json
decoded-image.dat002-decoded-image.dat

Visualization

The following fingerprint image can be reconstructed from this stage's binary data. Visualization itself is not part of transparency data.

Black fingerprint image on white background
Original fingerprint image as decoded by SourceAFIS.

Binary data

Image size can be obtained from dimensions field in the associated json data, height first. Binary data consists of rows of pixels ordered from top to bottom. Every row consists of pixels ordered left to right. Every pixel is a 64-bit IEEE754-encoded big-endian floating-point number in range from 0 (white) to 1 (black).

Example: 002-decoded-image.dat (145,112 scalars, range 0 to 1, average 0.11)

Json

Json data describes basic properties of the binary data, most importantly dimensions of the image.

Example: 001-decoded-image.json

{
  "axes": [
    "y",
    "x"
  ],
  "dimensions": [
    374,
    388
  ],
  "scalar": "double",
  "bitness": 64,
  "endianness": "big",
  "format": "IEEE754"
}