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Mesh glyph outlines

Source: R/text.R
lari_glyphs.Rd

Turn glyph rings into constraint segments and triangulate them, one mesh per glyph (the default) or one mesh for the whole string (merge = TRUE). Holes come from the constraint depth: with the default erase = "holes" only odd depth is kept, so a counter (depth 2) is a hole and the orientation of the rings does not matter. erase = "outer" keeps the counters as part of the mesh (their depth tells them apart).

Usage

lari_glyphs(
  outline,
  merge = FALSE,
  max_area = NULL,
  min_angle = NULL,
  min_edge_length = NULL,
  erase = c("holes", "outer", "hull"),
  ...
)

Arguments

outline

a data frame of rings, see Details

merge

if TRUE triangulate all glyphs in one mesh, so overlapping glyphs cross and stack in depth; otherwise mesh each glyph separately and bind the tables

max_area

maximum triangle area, NULL for none

min_angle

minimum triangle angle in degrees, NULL for none. Above about 20.7 degrees termination is not guaranteed by theory; the floor keeps it finite.

min_edge_length

the edge-length floor; NULL chooses default_min_edge_length() from the current segments and the area bound, taking the smaller of max_area and the finest area the sizing field asks for so a sizing field is honoured rather than capped; 0 never gives up

erase

which triangles to keep: "holes" (odd depth, the letter shapes), "outer" (depth > 0, letters with their counters filled), "hull" (all, including the space around each letter)

...

passed to lari_triangulate() (size, max_steiner, ...)

Value

a list like lari_triangulate(): vertices, triangles and segments tables (rows of vertices index the whole result) with a glyph column (NA for triangles when merge = TRUE), and report, one row per mesh. The vertex id column is local to each glyph's mesh.

Details

outline is a data frame with x, y and ring and glyph id columns. The output of lari_text_outline() (glyph, ring), of systemfonts::glyph_outline() (glyph, contour) and of string2path::string2path() (glyph_id, path_id) are recognised as they are. A ring may repeat its first vertex at the end, or not.

See also

lari_text(), lari_text_outline()

Examples

## a square "O": an outer ring and a hole ring, as a glyph would give
o <- data.frame(x = c(0, 1, 1, 0, 0.3, 0.7, 0.7, 0.3),
                y = c(0, 0, 1, 1, 0.3, 0.3, 0.7, 0.7),
                glyph = 1L, ring = rep(1:2, each = 4))
r <- lari_glyphs(o, max_area = 0.01)
nrow(r$triangles)
#> [1] 134