Mist

A signed distance field generator with support for Viktor Chlumský's MSDF technique.

Usage

This project tracks the latest tagged version of Zig, which is 0.17 currently. A simple example can be found below, with a more in-depth one in example/generate.zig.

const Generator = @import("mist");
const font_data = @embedFile("OpenSans-Bold.ttf");

var gen: Generator = try .create(font_data);
defer gen.destroy();

var seed: u64 = undefined;
io.random(std.mem.asBytes(&seed));

const gen_opts: Generator.Options = .{
    .sdf_type = .mtsdf,
    .px_size = 64,
    .px_range = 8,
    .coloring_rng_seed = seed,
    .validate_shape = true,
    .normalize_shape = true,
    .orient_contours = true,
};

for ([_]u21{ 'A', 'B', 'C' }) |codepoint| {
    const data = try gen.generateSingle(allocator, codepoint, &gen_opts);
    defer data.deinit(allocator);
    
    var image: stbi.Image = try .createEmpty(
        data.glyph_data.width,
        data.glyph_data.height,
        gen_opts.sdf_type.numChannels(),
        .{},
    );
    defer image.deinit();
    @memcpy(image.data, data.pixels);

    var path_buf: [64]u8 = undefined;
    const path = try std.fmt.bufPrintZ(&path_buf, "{u}_sdf.png", .{codepoint});
    try image.writeToFile(path, .png);
}

Modules

The package provides two modules:

• mist — the full library: the freetype-backed font frontend (glyph outlines, metrics, kerning, atlas packing) on top of everything below. Requires libc.
• mist-core — just the SDF generation core. It has no dependencies: no freetype, no libc, so it builds for freestanding targets such as wasm32-freestanding. Feed it outlines yourself (e.g. from your own font parser) through ShapeSink:

const mist = @import("mist-core");

var shape: mist.Shape = .{};
defer shape.deinit(allocator);

var sink: mist.ShapeSink = .{ .allocator = allocator, .shape = &shape, .scale = 1.0 / font_units_per_em };
try sink.moveTo(.{ x0, y0 });
try sink.lineTo(.{ x1, y1 });
try sink.quadTo(.{ cx, cy }, .{ x2, y2 });

const glyph = try mist.generateSingle(allocator, &shape, .{
    .advance = advance,
    .bearing_x = bearing_x,
    .bearing_y = bearing_y,
}, &gen_opts);
defer glyph.deinit(allocator);

Note

The library exposes a similar set of functionality to Chlumský's work, but it's not intended to be its equivalent, some features will be implemented differently and some will be intentionally omitted. Issues and PRs can still compare to msdfgen, like if the library generates a less correct SDF than it, but direct ports, or the request for them will be closed.