msdf-zig

A Zig implementation of Viktor Chlumský's multi-channel signed distance field generator.

Requires Zig 0.17.0-dev.1465+8b2d0ce21 or newer.

Usage

const Generator = @import("msdf-zig");
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);
}

A more in-depth example can be found in example/generate.zig.

FreeType-free shape generation

Consumers that already have vector geometry can import msdf-core without fetching or linking FreeType and turbopack. Build a Shape from Shape.Contour and EdgeSegment values, then call:

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

const opts: msdf.Options = .{
    .sdf_type = .msdf,
    .px_size = 64,
    .px_range = 8,
};
const data = try msdf.generateFromShape(allocator, &shape, &opts);
defer data.deinit(allocator);

Pass -Dfont=false when building only the core module. Shape preprocessing and coloring use the same implementation as the font generator. Core options contain only geometry and raster controls; variable-font and atlas concurrency settings remain on Generator.Options.

Output channels use msdfgen-compatible UNORM rounding. The experimental msdf10 format stores three 10-bit distance channels in four bytes per pixel.

Disclaimer

This library might provide an option for it later, but you currently need to preprocess your fonts manually to resolve overlapping contours (if the font has them).