Export JSON Container

When configured to use the JSON format, an Export call to the SDK outputs a single JSON encoded file containing all captured prints. Print images are Base64 encoded and can be PNG, WSQ, BMP or RAW format images. In addition it can contain an Audit Image (a low resolution, print obscured, version of the captured image) for the purpose of human audit.

Fingerprint images are held inside a Fingerprints array, and will appear as follows:

CODE

"Fingerprints" : [
         {
            "CaptureDate" : {
               "DateTime" : "2019-04-17T11-01-12.49+01:00"
            },
            "FingerImpressionImage" : {
               "BinaryBase64ObjectPNG" : "qla7JgoqN+8Zh+K4NYkpFN1Qdml0QOtFNYji",
               "BinaryBase64ObjectRAW" : "",
               "BinaryBase64ObjectWSQ" : "",
               "BinaryBase64ObjectBMP" : "",
               "Height" : 477,
               "ImageBitsPerPixelQuantity" : 8,
               "ImageHashValuePNG" : "df28fb51b26aa78c38b4b28fac5a254fddc8b42631928f61878cde66c693ca94",
               "ImageHashValueRAW" : "",
               "ImageHashValueWSQ" : "",
               "ImageHashValueBMP" : "",
               "Resolution" : 500,
               "Width" : 280
            },
            "FingerPositionCode" : 7,
            "NFIQ" : 1
         },
         {
                ......next print
         }
]

The following objects and values can be present within a Fingerprint:

Value	Description
DateTime	Date and time of capture.
FingerImpressionImage	Object containing print data.
BinaryBase64ObjectPNG	Base64 encoded PNG image of a single fingerprint.
BinaryBase64ObjectRAW	Base64 encoded RAW image of a single fingerprint.
BinaryBase64ObjectWSQ	Base64 encoded WSQ image of a single fingerprint.
BinaryBase64ObjectBMP	Base64 encoded BMP image of a single fingerprint.
Height	Image height in pixels.
Width	Image width in pixels.
Resolution	Image resolution in dots per inch.
ImageBitsPerPixelQuantity	Number of bits per pixel. Will always be 8.
ImageHashValuePNG	SHA256 hash of image contained in BinaryBase64ObjectPNG before Base64 encoding.
ImageHashValueRAW	SHA256 hash of image contained in BinaryBase64ObjectRAW before Base64 encoding.
ImageHashValueWSQ	SHA256 hash of image contained in BinaryBase64ObjectWSQ before Base64 encoding.
ImageHashValueBMP	SHA256 hash of image contained in BinaryBase64ObjectBMP before Base64 encoding.
FingerPositionCode	NIST specification for labelling fingers (see below).
NFIQ	Present when enabled, the NFIQ score of the print .
FingerprintImageFingerMissing	Deprecated

Fingertip images are indexed using the NIST specification:

1: Right thumb
2: Right index finger
3: Right middle finger
4: Right ring finger
5: Right little finger
6: Left thumb
7: Left index finger
8: Left middle finger
9: Left ring finger
10: Left little finger

When the SDK is configured to save an Audit image, an AuditImage_Left and/or AuditImage_Right object will be written at the top level of the JSON file. It contains a JPEG image in (Base64 encoded), and a hash. For example,

CODE

 "AuditImage_Left" : {
         "BinaryBase64ObjectJPG" : "/9j/4AAQSkZJRgABAQAAAQehg9Ef/9k=",
         "ImageHashValueJPG" : "a62ef823f1fc14ef6e585edfbdf31795c7725e97d5b86396ab8861d376cb6396"
  },

JSON output also supports writing of multiple scales (refer to Performing Matching against Legacy Databases). When multiple scales are configured, 3 sets of Fingerprints arrays are written as follows:

CODE

{
   "SCALE085" : {
      "Fingerprints" : [

      ],
       "Status" : 1
     },
     "SCALE100" : {
        "AuditImage_Left" : { },
       "Fingerprints" : [

       ],
        "Status" : 1
     },
     "SCALE115" : {
       "Fingerprints" : [

       ],
        "Status" : 1
     },
}