Dynamsoft Barcode Reader Auto-Restores Incomplete Parts of QR Codes and Data Matrix

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If you’ve ever managed barcode technology, you’re familiar that sometimes a physical barcode can be incomplete. For example, sometimes a corner of one might be missing due to poor printing or damage. For QR Codes and Data Matrix codes, this can cause the finder patterns to be obscured. 

The morphology of 2D matrix codes are made up of finder patterns. These finder patterns in QR Codes consist of three identical structures that are located in all corners except the bottom right. With a Data Matrix code, this L-shaped finder pattern and the dashed borders are vital for localizing. Naturally, partially missing finder patterns cause problems for a scanner to detect matrix codes.

With the introduction of Dynamsoft Barcode Reader v7.3, we have made available the capability to auto-restore – or auto-complete – missing portions of a QR code or a Data Matrix code from poor printing or damage.

How Incomplete QR Codes are Restored

Our updated algorithm tries to complete any missing positioning information based on the FinderPattern, the TimingPattern, the Border, its size, etc.

How Incomplete QR Codes are Restored

Let’s look at the following QR code as an example:

QR code before restoring the finder pattern

In the image, the two square patterns of the QR Code at the left edge are damaged – a part of them has been cut off. In this case, the auto-restore algorithm will complete these two squares based on:

  • the information of the known square pattern in the upper right corner
  • the TimingPattern connected to the two partially missing squares

Below is how it looks after restoring the finder pattern.

QR code after restoring the finder pattern

How Incomplete Data Matrix Codes are Restored

When the barcode reader detects there is data missing from the L-shaped finder pattern or the dashed borders in a Data Matrix code, the completion algorithm kicks in. The first step is to determine whether there are blocks in the code area. Based on the size of the code, a Data Matrix code can consist of multiple blocks or only one block. 

How Incomplete Data Matrix Codes are Restored

(1) Large Data Matrix codes with blocks

When a Data Matrix code has more than 26 x 26 modules (more than 24 x 24 modules for data), it is divided in blocks, as seen below. Each separated block does not exceed 24 modules on a side. This structure prevents distortion of the code.

For these codes, the restoration algorithm will use the alignment pattern closest to the missing border to estimate the missing border. 

(2) Data Matrix codes without blocks

For smaller codes without blocks, the restoration algorithm will estimate the position of the missing border based on the size information of the code.

For more information, read this post on How to Read Damaged Barcodes.

Licensing

This feature is integrated into all editions of Dynamsoft Barcode Reader and requires no extra licenses. Supported editions include Windows, Linux, iOS, Android and JavaScript.

Getting Started

API documentation 

Dev guide

Try Dynamsoft Barcode Reader online demo or download a 30-day free trial.

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