Re: coloured characters

From: William_J_G Overington (
Date: Thu Dec 23 2010 - 03:44:20 CST

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    I hope that the following will be helpful.
    There is a part of the Unicode character map that is named as the Private Use Area. (In fact, there are three such areas, but that is a more advanced topic, so just thinking about one Private Use Area is a good way to start the learning process.)
    The document about that part of the Unicode character map for Unicode 6 is not yet available, so here is a link to the version for Unicode 5.2.

    Starting on page 14 of that pdf document is some information about Private-Use Characters that can be located in the Private Use Area.
    Anyone can use the Private Use Area as he or she chooses. The Private Use Area provides a way to use special characters of one's own within the general framework of Unicode characters. Lots of people use the Private Use Area for various purposes. Many of those uses are for small groups of people, such as people working on rare languages or transcribing old manuscripts into computers.
    However, some mobile telephone manufacturers started to use the Private Use Area for encoding symbols, often colourful, (sometimes known as emoji), so that people sending text messages could send those symbols as well. Yet the mobile telephone manufacturers did not use the same encodings as each other and, because anyone can define characters in the Private Use Area, the encodings were not interchangeable and were not unique.
    So, if a message sent using a mobile telephone were to be stored in a computer database, there could be problems over what the Private Use Area codes were intended to mean.
    So, a solution was needed. The solution was to encode the characters into regular Unicode.
    There is a very useful document that was produced during the encoding process that is still available.

    The version available now is the version as at 27 April 2010.
    The document is large, 3.11 Megabytes, so can take a time to download, yet it includes lots of interesting information about the original encodings on mobile telephones and the Private Use Area encoding in plane 15 that Google devised.
    On page 56 of the document is the entry for GREEN HEART.
    I do not understand all of it myself, yet there are plane 0 Private Use Area codes such as U+EAA8 and U+E32B and images of green hearts.
    So, U+1F49A in regular Unicode is specifying a character so that messages using the GREEN HEART symbol can be expressed uniquely.

    As for the backslash fill, there is a system that started several hundred years ago for expressing colours with black and white lines. It was used for printing details of the colours of shields in "coats of arms" in books about heraldry.

    The system is often called the "Petra Sancta" system.
    Although the character GREEN HEART was encoded so as to solve the problem about mobile telephone characters, the character is available for everybody to use for other purposes as well.
    I hope that this helps.
    William Overington
    23 December 2010

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