Tag characters and in-line graphics (from Tag characters)

[William_J_G Overington]

Tag characters and in-line graphics (from Tag characters)
This document suggests a way to use the method of a base character together with tag characters to produce a graphic. The approach is theoretical and has not, at this time, been tried in practice.
The application in mind is to enable the graphic for an emoji character to be included within a plain text stream, though there will hopefully be other applications.
The base character could be either an existing character, such as U+1F5BC FRAME WITH PICTURE, or a new character as decided. Tests could be carried out using a Private Use Area character as the base character.
The explanation here is intended to explain the suggested technique by examples, as a basis for discussion. In each example, please consider for each example that the characters listed are each the tag version of the character used here and that they all as a group follow one base character.
The examples are deliberately short so as to explain the idea. A real use example might have around two hundred or so tag characters following the base character, maybe more, sometimes fewer.
Examples of displays:
Each example is left to right along the line then lines down the page from upper to lower.
7r means 7 pixels red
7r5y means 7 pixels red then 5 pixels yellow
7r5y-3b means 7 pixels red then 5 pixels yellow then next line then 3 pixels blue
Examples of colours available:
k black
n brown
r red
o orange
y yellow
g green (0, 255, 0)
b blue
m magenta
e grey
w white
c cyan
p pink
d dark grey
i light grey (thus avoiding using lowercase l so as to avoid confusion with figure 1)
f deeper green (foliage colour) (0, 128, 0)
Next line request:
- moves to the next line
Local palette requests:
192R224G64B2s means store as local palette colour 2 the colour (R=192, G=224, B=64)
7,2u means 7 pixels using local palette colour 2
Local glyph memory, for use in compressing a document where the same glyph is used two or more times in the document:
3t7r means this is local glyph 3 being defined at its first use in the document as 7 red pixels
3h here local glyph 3 is being used
The above is for bitmaps. It would be possible to use a similar technique to specify a vector glyph as used in fontmaking using on-curve and off-curve points specified as X, Y coordinates together with N for on-curve and F for off-curve. There would need to be a few other commands so as to specify places in the tag character stream where definition of a contour starts and so as to separate the definitions of the glyphs for a colour font and so on. This could be made OpenType compatible so that a received glyph could be added into a font.
Please feel free to suggest improvements. One improvement could be as to how to build a Unicode code point into a picture so that a font could be transmitted.
William Overington
27 May 2015
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