datamatrix is a commandline utility for reading and verifying Datamatrix direct part markings. Some image processing functions are based on visionutils.

Key features

• Reads PNG files (recommended at least 800 pixels across) using lodepng
• Outputs the plain text encoded by the datamatrix pattern
• Implemented in pure C99
• Supports GS1 semantics and digital links
• Can generate quality metrics for verification reports
• Parallelized with OpenMP
• No dependencies or software supply chains!

Build

Install the build system:

sudo apt install build-essential

Then compile.

make

And finally install.

sudo make install

Command options

-f --filename [PNG file]      Filename of a PNG file containing the datamatrix image
--square                      Matrix is expected to be square
--rectangle                   Matrix is expected to be rectangular
--quality                     Show quality metrics for verification reports
-o --output [PNG file]        Save an image showing the detected datamatrix
-g --grid [PNG file]          Save an image showing the detected grid
--hist [PNG file]             Save reflectance histogram
--shape [PNG file]            Save cell shape variance image
-t --template [TEX file]      Path for verification report template
-r --report [TEX file]        Filename to save a verification report as
-l --logo [image file]        Logo image to be shown at top of verification report
--histcentres                 Only sample grid cell centres for reflectance histogram
--mingrid [8..144]            Minimum matrix dimension
--maxgrid [8..144]            Maximum matrix dimension
--debug                       Show debugging information
--csv                         Show quality metrics in CSV format
--json                        Show quality metrics in JSON format
--yaml                        Show quality metrics in yaml format
--freq [8..144]               Set the matrix dimension
--erode [0..20]               Set erosion itterations
--dilate [0..20]              Set dilation itterations
--meanlight [0..20]           Set mean light threshold
--darklight [1..10]           Sampling step size when calculating peak dark and light
--maxhigh [6..90]             Maximum percent of high pixels after thresholding
--resolver [url]              GS1 resolver (eg. https://id.gs1.org)
--sampleradius [pixels]       Radius for sampling each grid cell
--minsegmentlength [pixels]   Minimum edge segment length for segment joining
--resizewidth [pixels]        Width of image after resizing from original
--resizeheight [pixels]       Height of image after resizing from original
--binwidth [pixels]           Width of the binary image used for perimeter detection
--raw                         Show the raw decoded text
--aperture [ref]              Aperture reference number from ISO 15416
--light [nm]                  Peak light wavelength used in nanometres
--angle [90|45]               Angle of illumination in degrees
--address1 [text]             First line of address on verification report
--address2 [text]             Second line of address on verification report
--address3 [text]             Third line of address on verification report
--phone [number]              Telephone number on verification report
--email [address]             Email address on verification report
--web [url]                   Website url on verification report
--footer [text]               Footer shown on verification report
--tests                       Run unit tests

Example usage

datamatrix -f examples/01.png

When possible, decoded text will appear in a more verbose human readable form. However if you want to know what text the datamatrix directly encodes then you can use the --raw option.

datamatrix -f examples/01.png --raw

When decoding GS1 datamatrix symbols you can also specify a GS1 resolver if you want a digital link to be returned.

datamatrix -f examples/01.png --resolver https://id.gs1.org

If you set the resolver as a '.' character then the GS1 code will be shown with brackets, such as (01)00068780000108(13)301231(10)ABC123.

datamatrix -f examples/01.png --resolver .

If you know the range of grid dimensions which are expected then you can narrow down the search using the --mingrid and --maxgrid options.

datamatrix -f examples/01.png --mingrid 10 --maxgrid 20

If needed, an image can be saved showing the detected datamatrix region and also the grid.

datamatrix -f examples/01.png -o detection.png -g grid.png

If you want to calculate quality metrics for symbol verification purposes:

datamatrix -f examples/01.png -o detection.png -g grid.png --quality

When showing quality metrics you can also generate a reflectance histogram, for use in a verification document. The option --modulecentres may also be used to only sample the module centres when creating the histogram.

datamatrix -f examples/01.png -o detection.png -g grid.png --quality --histogram reflectance.png

The --shape option also can be used to save an image showing variations in grid cell shape. This is only really useful for round or dot peen type markings.

datamatrix -f examples/01.png -o detection.png -g grid.png --quality --histogram reflectance.png --shape cell_shape.png

Metrics can also be output in CSV, JSON or yaml formats, for easy import into other systems.

datamatrix -f examples/01.png -o detection.png -g grid.png --quality --csv
datamatrix -f examples/01.png -o detection.png -g grid.png --quality --json
datamatrix -f examples/01.png -o detection.png -g grid.png --quality --yaml

Optionally, if you want debugging information and images for each decoding stage:

datamatrix -f examples/01.png --debug

Producing Verification Reports

A verification report in accordance with GS1 2D Barcode Verification Process Implementation Guideline may be produced with:

datamatrix -f examples/01.png --report myreport.tex

These reports are in LaTeX format, and you can also set contact details, the report image filenames and a custom header logo as follows:

datamatrix -f examples/01.png --report myreport.tex --address1 "Address line 1" --address2 "Address line 2" --address3 "Address line 3" --phone "123456789" --email "myemail@address" --web "https://mywebsite" --logo mylogo.png -o detection.png --hist histogram.png

Testing

Unit tests may be run with:

datamatrix --tests

If you want to test how well the decoding works with a specific settings:

datamatrix -f examples/01.png --debug \
    --erode [value] --dilate [value] \
    --meanlight [value]

erode and dilate values are in pixels. meanlight is typically in the range 0-20.

A set of images will be produced which show the detection process at each stage.

References

Data Matrix

Edge linking

GS1 General Specifications

GS1 2D Barcode Verification Process Implementation Guideline

Line–line intersection

Popular ISO/IEC 15434 Barcode Formats

Reed–Solomon error correction

The Health Industry Supplier Labeling Standard for Patient Safety & Unique Device Identification (UDI)