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NFIMM

The NFIMM (NIST Fingerprint Image Metadata Modifier) is available for Windows and Linux. It builds on MacOS but has not been tested.

NFIMM is written in C++ and built into a software library. This affords users to write their own using-application.

All computer-system requirements to build and store NFIMM are fairly minimal and are easily satisfied by modern hardware and software tools. All software dependencies and tools used to compile source code and implement functionality are available at no cost.

Across all operating systems, C++17 or higher is required to compile.

NFIMM Purpose

NFIMM has one major purpose: to update an image-file's resolution metadata.

When an image is down- or up-sampled, its resolution metadata should be updated to reflect the "new" resolution.

For those image compression-types that support additional information, like PNG, new metadata may be inserted.

NFIMM does not modify the image-file's image-data; it is "transferred" to the newly generated image.

Quick Start

Since NFIMM is designed as a software library, a driver is included in this distribution for convenience.

The binary and its source code provide the following:

1. Run out-of-the-box to validate the build
2. Demonstrate how to use the NFIMM library
3. Serve as starting-point for user to write their own using-application

Windows Build

Using cmake and MSBuild, build the library and executable.

**********************************************************************
** Visual Studio 2022 Developer Command Prompt v17.8.6
** Copyright (c) 2022 Microsoft Corporation
**********************************************************************

C:\Program Files\Microsoft Visual Studio\2022\Enterprise>cmake --version
cmake version 3.22.3

CMake suite maintained and supported by Kitware (kitware.com/cmake).

C:\Program Files\Microsoft Visual Studio\2022\Enterprise>MSBuild --version
MSBuild version 17.8.5+b5265ef37 for .NET Framework
17.8.5.5502

Create and change-to build subdir:

NFIMM\build> cmake .. -DCMAKE_CONFIGURATION_TYPES="Release" -D_WIN32_64=1
NFIMM\build> MSBuild NFIMM_ITL.sln

See also file ./build_commands.txt.

Complementary Binary

This simple binary exercises the NFIMM library and generates a "new" image.

Note that for the runtime command below, the -m switch is not required because PNG is serviced by default, and the source-image sample rate is optional (-a).

.\NFIMM\build\src\bin\Release> NFIMM_bin.exe -b 500 -c inch -s ..\img\src\ducks_grey.png -t ..\img\dest\ducks_grey_comp.png -e "Description:Original image downsampled from 600PPI" "Author:NIST-ITL" "Comment:for NFIMM pub release" "Creation Time:file" -z

Check the Result

There should be a new ducks_grey.png image here:

NFIMM\img\dest> dir

    <DIR>          .
    <DIR>          ..
           191,986 ducks_grey.png
           191,986 ducks_grey_comp.png

The generated and "compare" image headers should be identical except timestamp.

Example Usage Scenario by NFIR

The NIST Fingerprint Image Resampler (NFIR) library is utilized to downsample a PNG source image's image-data from 600 to 500 PPI (pixels per inch); the 500PPI image (known as the "destination") is saved to the file system. In order to be most correct after resampling, the destination image sample rate (resolution/DPI) header info should be updated to reflect the new sample rate.

Get NFIR here: https://github.com/usnistgov/NFIR

After the downsample, NFIR calls NFIMM and passes it the following image metadata parameters:

Table 1 - NFIMM metadata parameters for NFIR example

For PNG, NFIMM programatically inserts the following tEXt chunk key:value pairs:

   Comment:[ Updated pHYs | Inserted pHYs] 
   Software:Header mod by NFIMM

Note that specified source and destination sample rate applies to the horizontal and vertical "rows and columns" (of the image).

NFIMM API

The following are supplied by the NFIMM user/caller:

1. Source image PATH or bytes-stream (std::vector<uint8_t>)
2. Destination (aka target) image PATH
3. Source and destination image metadata:

• Required
  • source image compression format
  • destination image sample rate
  • destination image sample rate units
• Optional
  • source image sample rate
  • PNG custom text: Description, Author, Creation Time, etc.

Note that the destination image compression format is constrained to be the same as the source image and therefore is not a required input parameter.

Table 2 lists the available metadata parameters:

PNG Custom Text

There are two custom text-chunks that are programmatically created and inserted into the destination header by default:

• Software:NFIMM version, and either
• Comment:NFIMM updated source pHYs resolution from {src-img} to {dest-img}PPI, or
• Comment:NFIMM inserted pHYs resolution as {dest-img}PPI

Also, at lease one custom text-chunk is required to be supplied by the caller of NFIMM.

Miscues/Exceptions

All caught exceptions cause the library to abort and throw the exception message to the user.

Doxygen

See README under ./doc directory.

Contact

Project Lead: John Libert (john.libert@nist.gov)

Developer NFIMM: Bruce Bandini (bruce.bandini@nist.gov)

Disclaimer

See the NIST disclaimer at https://www.nist.gov/disclaimer