yDots webtools: decoder constructor comparator

yellow dots

The most common way to implement MIC in printing is by using miniature yellow dots that are invisible to the naked eye. MIC is always printed multiple times on the document. The dots are not visible due to two main factors:

MIC can contain various types of information. Some examples include: Not all color laser printers print MIC. The Electronic Frontier Foundation (EFF) has published a list of some laser printers that print MIC based on tests. The MIC of each printer is unique. It is not possible for two different printers to print the same sequence of yellow dots.

scanning MIC

Tracking yellow dots is done by scanning and properly setting the scanning parameters. The key parameters in this process are DPI and compression.

DPI

DPI scanning represents the most important scanning parameter. The ideal state is the highest possible DPI because the larger the resolution, the more detail of the yellow dots can be captured in the image.

Comparison of 1200, 600 and 300 DP scans. (filter)

Image contains scans of yellow dots under different DPI profiles. In order to make the dots visible, the green and blue channels of the RGB color model are switched on the image, making the dots appear as purple. Illustrations that are modified by this change are labeled with the designation "(filter)" in the description.

Compression

Compression can reduce the overall quality of the resulting image and thus blur the dots. The best option is to use a lossless format, such as PNG.

Comparison of LOW and HIGH compression setting. (filter)

Some scanners do not have this option, so it is advisable to set the lowest possible compression value.

frequency of MIC occurrence

To get an overview of the occurrence of MIC, 130 different random prints were collected, which were:

The aim was to avoid private or company internal printing and thus map the occurrence of MIC in freely available documents.

Subsequently, the prints were scanned with high resolution 1200 DPI without compression, in order to confirm the presence of yellow dots. The total number of samples with yellow dot content was 51 out of 130 prints.

Occurrence of MICs by content category.
CategoryMIC positiveMIC negativeTotal
Certifications639
Invitation cards8614
Vouchers, tickets6511
Information brochures11415
Advertising leaflets144559
Correspondence41317
Others235
Total5179130

MIC patterns

MIC is present throughout the printed document in repeating sequences. It forms a two-dimensional matrix, in which a dot represents a Boolean value.

The pattern determines the method and rules for the sequential encoding of MIC. It is quite common for multiple manufacturers to use the same type of pattern, or for one manufacturer to use multiple patterns on different printer models.

A single printer can use only one type of pattern.

Basic properties of patterns

Each pattern for MIC encoding defines:

These properties are always the same for every document printed with the given pattern. This means that the MIC of a document printed on printers from two different manufacturers will have the same properties if they use the same pattern.

Layout

Regardless of the pattern used, the MIC print is always repeated across the entire surface of the paper. The parameter that changes depending on the type of pattern is the layout method.

There are three layout methods for MIC printing:

Grid layout

Patterns that use the grid layout print the MIC in columns and rows. Each cell of this grid contains the MIC, so there is no shift or gap between repeating MIC patterns.

Grid layout. The boundaries of the MICs are marked with red lines. (filter)
Checkerboard layout

The MIC is printed the same way as in the grid layout, but every other cell in the row of the grid does not contain the MIC. Every other row is shifted by one horizontal position, creating the checkerboard layout.

Checkerboard layout. The boundaries of the MICs are marked with red lines. (filter)
Diagonal layout

The MIC is printed in adjacent columns, with each subsequent column containing a vertical shift by a predetermined constant. The shift for a particular pattern is always the same for all MIC prints made according to it.

Diagonal layout. The boundaries of the MICs are marked with red lines. (filter)

Static segment

Most patterns contain a small static segment that is always located at the same position of the MIC matrix. The static segment helps determine the pattern type and the boundaries of individual MICs.

Example of static segments. The static segments are marked with green lines. The boundaries of the MICs are marked with red lines. (filter)

This part of the MIC is always the same on all impressions of a given pattern and always violates the dot printing rules defined by the pattern. This is done so that the same dot sequence cannot appear in the part of the MIC that encodes information.

For example, if the pattern does not allow printing dots in adjacent cells, the static segment can violate this rule and print dots in two cells that are immediately next to each other.

Information encoding

Each pattern type uses a unique method of encoding information into a two-dimensional matrix. There is a pattern that simply encodes information binary into columns, but there is also a pattern whose encoding method remains unknown. The encoding method is divided into: