Outlines

Read an outline when you draw glyphs yourself, in SVG, on a canvas, or in a PDF, or when you need a tight bounding box. glyphOutline() returns the contour geometry of one glyph as neutral path commands in design units; drawing it is left to your code.

Read an outline

Start from a glyph identifier, here the one of o:

<?php

$glyphId = $font->glyphMetrics('o')->glyphId;
$outline = $font->glyphOutline($glyphId);

if ($outline->isEmpty()) {
    // Spaces and other non-drawing glyphs have no contours.
}

foreach ($outline->contours as $contour) {
    foreach ($contour->commands as $command) {
        // M, L, Q, or Z with their design-unit coordinates.
    }
}

M, L, Q, and Z are move, line, quadratic curve, and close-path commands, the same vocabulary as an SVG path.

Filled points are contour endpoints; hollow points are quadratic controls. The enlarged segment is taken directly from glyphOutline(). A control point need not lie on the curve. ALTO's commands include implied endpoints, so these markers are not an inventory of the original stored font points.

Transform geometry

Outlines, contours, and path commands accept a two-dimensional affine transform:

<?php

$scale = 16 / $font->face()->unitsPerEm;

$scaled = $outline->transform(
    xx: $scale,
    yx: 0,
    xy: 0,
    yy: -$scale,
    dx: 0,
    dy: 16,
);

The example scales the outline to 16 units, flips the font's upward Y axis, and moves the baseline. It still does not draw the result.

Contract

GlyphOutline exposes glyphId and a list of contours. Each contour exposes its commands (M, L, Q, or Z). isEmpty(): bool reports whether there are no contours. transform(float $xx, float $yx, float $xy, float $yy, float $dx, float $dy): GlyphOutline returns a new affine-transformed outline. Unsupported outline structures raise UnsupportedFontException; only TrueType glyf outlines are read, see Tables.