Juraj's Blog

29 May 2021

Converting Slovak text to Braille

My visually-impaired friend asked me for help in developing a conversion tool for the Slovak text into the Braille code.

The idea was to convert the text into an equivalent Unicode Braille pattern . These could be further utilized, for example by 3D printing them into tactile signage.

The final result as an interactive convertor:


Braille alphabet consists of dots, which arranged in various patterns form cells. The cells represent a letter, a number or a punctionation mark.

Although Unicode supports 8-dot Braille cells, Slovak Braille only utilizes 6-dot cells, making our job slightly easier.

The six dots in a Braill cell

Please find various representations of letter h in the following table:

Letter h
Braille symbol
Unicode character U+2813

This means that to convert letters into their Braille representation in JavaScript, we need a conversion table, similar to the following:

    "a": 0x2801,
    "á": 0x2821,
    "ä": 0x2808,
    "b": 0x2803,
    "c": 0x2809,

Lower case

Using just the mapping table, we can solve the lower case letters, as we can map them now in a straightforward manner, but we still have numbers and upper case to deal with.

There are also a few symbols that are representes with multiple cells, such as % (⠼⠏) and @ (⠼⠻)


In both the numeric and upper case sequences, we need to use Braille formatting marks. These are the number sign ⠼ and the capital sign ⠠, which immediately precede the sequence they modify. The sequence then gets either terminated by another formatting mark or a white space.

In case of numbers, we need to find the sequence of numbers that is terminated either by a letter or a space and prefix it with the ⠼ number sign. If it’s not terminated by a space, append the prefix end ⠰.

Every number of the sequence gets looked up in the conversion table. Digits 1, 2, 3, through 0 are encoded as characters a, b, c through j, as the number sign ⠼ changes the meaning of the cells that immediately follow it.

Upper case

Similar to the number sequence, we need to find a longest unbroken upper case sequence, prefix it with the ⠠ capital sign. If the sequence is followed by a lower case letter, we end the sequence with a prefix end ⠰.

Every character of the upper case sequence is turned into its lower case variant and encoded via the lookup table.

Putting it all together

The rest is just consuming input text in a loop, checking for sequences of numbers, upper case letters, or handling everything else by a lookup table. into sequences of

The tool is in production , used by the Slovak Authority for the Braille Code .

The repository of the translator on GitHub .