# Outlines

HTML: [altophp.com/font/glyphs/outlines](https://altophp.com/font/glyphs/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.

![Inter o with contour endpoints and quadratic control points, plus a magnified real quadratic segment.](https://altophp.com/font/assets/figures/glyph-contours.svg)

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](https://altophp.com/font/tables.md).

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Previous: [Glyph metrics](https://altophp.com/font/glyphs/metrics.md)
Next: [Glyph names](https://altophp.com/font/glyphs/names.md)

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ALTO\FONT: [altophp.com/font](https://altophp.com/font/)
ALTO(PHP): [altophp.com](https://altophp.com/)