lofifonts: Text Rendering with Bitmap and Vector Fonts

Description

Alternate font rendering is useful when rendering text to novel graphics outputs where modern font rendering is not available or where bespoke text positioning is required. Bitmap and vector fonts allow for custom layout and rendering using pixel coordinates and line drawing. Formatted text is created as a data.frame of pixel coordinates (for bitmap fonts) or stroke coordinates (for vector fonts). All text can be easily previewed as a matrix or raster image. A selection of fonts is included with this package.

Author(s)

Maintainer: Mike Cheng mikefc@coolbutuseless.com [copyright holder]

Other contributors:

• June Choe jchoe001@gmail.com (Contributed character positioning code) [contributor]

• Frederic Cambus fred@statdns.com (Creator of 'spleen' font) [copyright holder, type designer]

• GNU Unifont authors (Creators of 'unifont') [copyright holder, type designer]

• Suraj Kurapati (Creator of 'Tamzen' font) [copyright holder, type designer]

• Scott Fial (Creator of 'Tamsyn' font upon which 'Tamzen' is based) [copyright holder, type designer]

• Anders Hoff (Creator of 'gridfont' font) [copyright holder, type designer]

See Also

Useful links:

• https://github.com/coolbutuseless/lofifonts

• Report bugs at https://github.com/coolbutuseless/lofifonts/issues

Create a data.frame of pixel coordinate information of the rendered text

Description

Create a data.frame of pixel coordinate information of the rendered text

Usage

bitmap_text_coords(text, font = "unifont", dx = 0L, dy = 0L, missing = NULL)

Arguments

Value

data.frame of coordinate information

char_idx

The index of the glyph within the provided text string

codepoint

Unicode codepoint (integer)

x

Pixel coordinate x value for display

y

Pixel coordinate y value for display

line

Line number within input text where this character appears

x0

Original untransformed x-coordinate

y0

Original untransformed y-coordinate

See Also

Other bitmap text functions: bitmap_text_matrix(), bitmap_text_raster()

Examples

bitmap_text_coords('Hi')

Create a binary matrix of the rendered text

Description

Create a binary matrix of the rendered text

Usage

bitmap_text_matrix(
  text,
  font = "unifont",
  dx = 0L,
  dy = 0L,
  scale_matrix = 1,
  missing = NULL
)

Arguments

Value

Binary matrix representation of the rendered text

See Also

Other bitmap text functions: bitmap_text_coords(), bitmap_text_raster()

Examples

bitmap_text_matrix('Hi')

Create a raster image of the rendered text

Description

Create a raster image of the rendered text

Usage

bitmap_text_raster(
  text,
  font = "unifont",
  dx = 0L,
  dy = 0L,
  scale_matrix = 1,
  missing = NULL
)

Arguments

Value

Raster image representation of the rendered text

See Also

Other bitmap text functions: bitmap_text_coords(), bitmap_text_matrix()

Examples

ras <- bitmap_text_raster('Hi')
plot(ras)

Convert a 'bittermelon' 'bm_font' to a lofi font

Description

Convert a 'bittermelon' 'bm_font' to a lofi font

Usage

convert_bm_font_to_lofi(font, font_name = "Unknown")

Arguments

Value

lofi font object

Examples

filename <- system.file("fonts/spleen/spleen-8x16.hex.gz", package = "bittermelon")
bmfont <- bittermelon::read_hex(filename)
lofi <- convert_bm_font_to_lofi(bmfont)
lofi

Fetch an included 'lofi' font

Description

Fetch an included 'lofi' font

Usage

get_lofi_font(font_name)

Arguments

Value

'lofi' font object. See lofi for details of this data structure

Examples

get_lofi_font('unifont')

Return the names of all included fonts

Description

Return the names of all included fonts

Usage

get_lofi_names(type)

Arguments

Value

List of two elements: names of bitmap fonts, names of vector fonts

Examples

get_lofi_names('bitmap')

A description of the 'lofi' font format used to store fonts for this package

Description

This package uses a custom data structure to store font information. This data structure is optimized for access to random sequences of glyphs which can be quickly assembled into a data.frame of points (for bitmap fonts) or strokes (for vector fonts). This data structure also needs to be compact and avoid unnecessary repetition. This is because the 'unifont' font contains pixel coordinates for over 100,000 codepoints and all this data must not exceed package size limitations for CRAN.

Details

Each 'lofi' font is a list object with the following members:

coords

A data frame of 'x', 'y' coordinates. For vector fonts this also includes a 'stroke_idx' to delineate the individual strokes within a single glyph. This is a simple concatenation of all points (or strokes) in a font. Extracting this font data for a particular codepoint requires the use of other indexing elements in the 'lofi' structure. NOTE: For bitmap fonts, (x, y) coordinates must be numeric, integer or raw values with no values below zero.

codepoint_to_idx

An integer vector. Use a codepoint (integer) to access the row index into the 'glyph_info' data.frame which holds the meta-information about this glyph. Because codepoints are indexed from 0, but R indexes vectors from 1, to access the row index: codepoint_to_idx[codepoint + 1]

line_height

Integer. The line height of this font in pixels

default_codepoing

Integer. The default unicode codepoint to use if the font does not contain a given glyph

baseline_offset

Numeric value. The offset between the bottom of the font data and the baseline for the text

name

name of font

glyph_info

A data.frame of meta-information about each glyph. One row per glyph

codepoint

Glyph codepoint (integer value)

npoints

The number of rows of data in 'coords' data.frame which are used to define this font

row_start

The index of the first row in 'coords' data.frame which contains data for this font

row_end

The index of the last row in 'coords' data.frame which contains data for this font

width

Glyph width (in pixels)

Usage

This section describes the process of extracting the data for a single glyph

1. Convert the glyph to an integer codepoint using codepoint <- utf8ToInt(x)

2. Use row <- codepoint_to_idx[codepoint + 1] to determine the row index of glyph_info which contains information for this codepoint.

3. if row is NA this indicates that the font does not support the glyph, and the row corresponding to default_codepoint should be used instead

4. info <- glyph_info[row, ]

5. Subset coords data.frame for the coordinates associated with this glyph: coords[info$row_start:info$row_end, ]

Examples

lifo <- get_lofi_font('unifont')
x <- 'a'
codepoint <- utf8ToInt(x)
row <- lifo$codepoint_to_idx[codepoint + 1]
info <- lifo$glyph_info[row,]
coords <- lifo$coords[seq(info$row_start, info$row_end), ]
coords
plot(coords$x, coords$y, asp = 1, ann = FALSE, axes = FALSE)

# Regular users should just use the functions provided in this package which
# add extra font information and layout sequences of characters 
# over multiple lines
bitmap_text_coords('a', 'unifont')
bitmap_text_raster('a', 'unifont') |> plot()

Plot a lofi raster

Description

Plot a lofi raster

Usage

## S3 method for class ''lofi-raster''
plot(x, interpolate = FALSE, ...)

Arguments

Value

None

Examples

ras <- bitmap_text_raster("Hi")
plot(ras)

Print summary information about a lofi font

Description

Print summary information about a lofi font

Usage

## S3 method for class 'lofi'
print(x, ...)

Arguments

Value

None

Examples

font <- get_lofi_font('unscii-8')
print(font)

Create data.frame of glyph information for the given text.

Description

Text input can contain multiple lines separated by carriage returns

Usage

vector_text_coords(
  text,
  font = c("gridfont_smooth", "gridfont", "arcade"),
  dx = 0L,
  dy = 0L,
  missing = utf8ToInt("?")
)

Arguments

Value

data.frame of stroke information

char_idx

The index of the character within the provided text string

codepoint

Unicode codepoint (integer)

stroke_idx

Index of the stroke within each character

x

Pixel coordinate x value for display

y

Pixel coordinate y value for display

line

Line number within input text where this character appears

x0

Original untransformed x-coordinate

y0

Original untransformed y-coordinate

See Also

Other vector text functions: vector_text_matrix(), vector_text_raster()

Examples

vector_text_coords('Hi')

Create a binary matrix of the rendered text

Description

Create a binary matrix of the rendered text

Usage

vector_text_matrix(
  text,
  font = c("gridfont_smooth", "gridfont", "arcade"),
  scale_coords = 1,
  scale_matrix = 1,
  dx = NULL,
  dy = NULL,
  missing = utf8ToInt("?")
)

Arguments

Value

Binary matrix rendering of the font

See Also

Other vector text functions: vector_text_coords(), vector_text_raster()

Examples

vector_text_matrix("Hi")

Create a raster image of the rendered text

Description

Create a raster image of the rendered text

Usage

vector_text_raster(
  text,
  font = c("gridfont_smooth", "gridfont", "arcade"),
  scale_coords = 10,
  scale_matrix = 1,
  dx = NULL,
  dy = NULL,
  missing = utf8ToInt("?")
)

Arguments

Value

Raster image of rendered text

See Also

Other vector text functions: vector_text_coords(), vector_text_matrix()

Examples

ras <- vector_text_raster("Hi")
plot(ras)