Hershey Font Format
hershey-font-format.RmdJHF - Hershey Font File format
The Hershey Font File format (.jhf) is a text file with encodings for all the glyphs in the font.
The text is hard-wrapped at 72 characters-per-line, so longer glyphs get split across multiple lines.
Glyph Encoding
The following is from Paul Bourke’s dataformats page.
The structure is basically as follows:
| Position | Interpretation |
|---|---|
| 0-4 | Identifier (integer) - not unique! |
| 5-7 | Number of vertices (integer) |
| 8 | Left position |
| 9 | Right position |
| … | Every pair of characters represents a vertex |
All vertex coordinates are given as a pair of characters. The numeric value of each vertex its ASCII value relative to the ASCII value of ‘R’.
The vertex coordinate of " R" indicates a pen up operation i.e. the drawing pen moves to the next location, but does not draw a stroke.
As an example consider the glyph: 8 9MWOMOV RUMUV ROQUQ
- ID = 8
- Number of vertices = 9 - this means there are a total of
2*9 = 18characters to decode. - Left position = ‘M’ (ASCII = 77). Relative to ‘R’ (ASCII = 82), this is
-5 - Right position = ‘W’ (ASCII = 87). Relative to ‘R’ =
+5 - First coordinate is “OM” = (-3,-5)
- Second coordinate is “OV” = (-3,4)
- Raise the pen " R"
- Move to “UM” = (3,-5)
- Draw to “UV” = (3,4)
- Raise the pen " R"
- Move to “OQ” = (-3,-1)
- Draw to “UQ” = (3,-1)
This glyph string can be converted to a data.frame (using hershey::convert_glyph_to_df()) and plotted with ggplot.
glyph <- ' 8 9MWOMOV RUMUV ROQUQ'
glyph_df <- hershey::convert_glyph_to_df(glyph)
glyph_df
#> x y left right width stroke idx
#> 1 -3 5 -5 5 10 0 1
#> 2 -3 -4 -5 5 10 0 2
#> 4 3 5 -5 5 10 1 3
#> 5 3 -4 -5 5 10 1 4
#> 7 -3 1 -5 5 10 2 5
#> 8 3 1 -5 5 10 2 6
ggplot(glyph_df, aes(x, y, group = stroke)) +
geom_point() +
geom_path() +
coord_equal() +
theme_minimal() +
scale_x_continuous(breaks = scales::pretty_breaks()) +
scale_y_continuous(breaks = scales::pretty_breaks())