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convert.js
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convert.js
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var parseUnit = require('parse-unit');
var defined = require('defined');
// Most browsers have a default font size of 16px
var DEFAULT_PX_SIZE = 16;
// Returns a pixel font size from a Opentype.js font and number / CSS string:
// Supported values: '1em', '24px', '32pt'
// Numbers and unit-less values are assumed to already be in pixels
module.exports.getFontSizePx = function (font, value, dpi) {
if (typeof value === 'number') return value;
if (typeof value !== 'string') throw new TypeError('Expected number or string for getFontPixelSize');
const parsed = parseUnit(value);
if (!parsed[1] || parsed[1] === 'px') {
return parsed[0];
}
if (parsed[1] === 'em') {
return parsed[0] * DEFAULT_PX_SIZE;
} else if (parsed[1] === 'pt') {
dpi = defined(dpi, 96);
return parsed[0] * dpi / 72;
} else {
throw new TypeError('Unsupported unit for fontSize: ' + parsed[1]);
}
};
// Returns actual EM units for the given value, e.g. 1em => 2048 units
module.exports.getEmUnits = function (font, fontSizePx, value) {
var parsed = typeof value === 'number' ? [ value, 'px' ] : parseUnit(value);
if (parsed[1] === 'em') {
return parsed[0] * font.unitsPerEm;
} else if (parsed[1] === 'px') {
var pxScale = 1 / font.unitsPerEm * fontSizePx;
return parsed[0] / pxScale;
} else {
throw new Error('Invalid unit for getPixelSize: ' + parsed[1]);
}
};
// Returns a scale for our paths that will match our desired font pixel size
module.exports.getScale = function (font, fontSizePx) {
return 1 / font.unitsPerEm * fontSizePx;
};