Lyon command-line tool

A simple program that exposes lyon's tessellators to the terminal.

USAGE:
    lyon [SUBCOMMAND]

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

SUBCOMMANDS:
    fuzz          tessellates random paths in order to find potential bugs
    help          Prints this message or the help of the given subcommand(s)
    path          Transforms an SVG path
    show          Renders a path in an interactive window
    tessellate    Tessellates a path

Commands

tessellate

Tessellates an SVG path. The output is a vertex buffer and an index buffer in text representation.

Run $> lyon tessellate --help for more details.

example

$> lyon tessellate "M 0 0 L 10 0  10 10 L 0 10 z"

This command prints to stdout:

vertices: [(0, 0), (10, 0), (0, 10), (10, 10)]
indices: [0, 1, 2, 2, 1, 3]

To read and write from files instead, see the -i <FILE> and -o <FILE>.

$> echo "M 0 0 L 10 0  10 10 L 0 10 z" > input.path
$> lyon tessellate -i input.path -o output.txt
$> cat output.txt
vertices: [(0, 0), (10, 0), (0, 10), (10, 10)]
indices: [0, 1, 2, 2, 1, 3]

The flag -c prints some stats instead of the actual tessellation:

$> lyon tessellate "M 0 0 L 10 0  10 10 L 0 10 z" -c
vertices: 4
indices: 6
triangles: 2

To specify the output format use --format <FORMAT_STRING>.

There are 3 format markers, one for vertices, indices and for triangles (triplets of indices). Each format marker starts with @, has a separator block ({sep=...}), a format block ({fmt=...} and it ends with @. In the blocks { and } characters have to be escaped!

list of format variables

• @vertices
  • {position.x} or {pos.x}
  • {position.y} or {pos.y}
• @indices
  • {index} or {i}
• @triangles
  • {index0} or {i0}
  • {index1} or {i1}
  • {index2} or {i2}

examples

$> lyon tessellate --format "vertices: [@vertices{sep=, }{fmt=({position.x}, {position.y})}@]" "M 0 0 L 10 0  10 10 L 0 10 z"
vertices: [(0, 0), (10, 0), (0, 10), (10, 10)]

$> lyon tessellate --format "@indices{sep=, }{fmt=[{index}]}@" "M 0 0 L 10 0  10 10 L 0 10 z"
[0], [1], [2], [2], [1], [3]

$> lyon tessellate --format '\{\n "triangles": \{\n@triangles{sep=,\n}{fmt=  "triangle": \{\n   "{i0}",\n   "{i1}",\n   "{i2}"\n  \}}@\n \}\n\}' "M 0 0 L 10 0  10 10 L 0 10 z"
{
 "triangles": {
  "triangle": {
   "1",
   "0",
   "2"
  },
  "triangle": {
   "1",
   "2",
   "3"
  }
 }
}

show

Opens a window with an interactive path viewer.

Run $> lyon show --help for more details.

example

$> lyon show -i assets/logo.path --fill --stroke --tolerance 0.05 --line-join Round --line-width 1.5

fuzz

This command runs the built-in fuzzer. The fuzzer will generate random paths and tessellate them until it finds a path that triggers an error. Once an error is found, the fuzzer tries to reduce the test case and prints the reduced test case to stdout.

Run $> lyon fuzz --help for more details.

example

$> lyon fuzz --max-points 12

path

Performs some given transformations on an SVG path. At the moment the only transformation implemented is flattening (approximating curve segments with successions of line segments).

Run $> lyon path --help for more details.