ISO IEC TR 29158:2011 pdf free
ISO IEC TR 29158:2011 pdf free.Information technology – Automatic identification and data capture techniques
The referenced matrix symbologies all require the locating of continuous modules in their reference decode algorithms. Some marking technologies are not capable of producing symbols with smooth, continuous lines when viewed by an imager. For example, dot peened symbols often produce unconnected dots. This section includes a method of pre-processing the image that will connect disconnected modules so that the standard reference decode algorithms can operate successully.
Once the grid of the symbol is determined, the location information is transferred to the evaluation of the reference greyscale image and subsequent processing occurs using the reference greyscale image.
This process is called the “stick function” and operates on the binarized image. The output is used for the initial decode using the reference decode algorithm. The steps below seek to connect areas in the image that are separated by less than one module, while not connecting areas which are separated by a distance of a module or more, for example alternating “clock teeth” modules.
Since a module size is not known during the execution of this algorithm, successively larger distance guesses are used within a range from the size of 50% of the smallest X-dimension to 1 10% of the largest X-dimension allowed by the application specification.
In addition, knowledge of the colour of “on” versus“off” modules is also required by the algorithm. Generally the“on”colour is dark for bright field ilumination and light for dark field ilumination. (For instance, the “on” colour is the colour of the “L” pattern of a Data Matrix symbol.) If a verifier does not “know” the colour of “on”,the algorithm may need to be repeated for each case.
Note: Implementers are free to optimize this algorithm (such as by attempting a better first guess of the correct stick size by analyzing the image), as long as the equivalent result is obtained.ISO IEC TR 29158 pdf download.
