canvas-with-twemoji/src/utils/getFontSizeByCssFont.js

Load emojis on canvas

const defaultHeight = 16;

module.exports = function getFontSizeByCssFont (cssFont) {
  if (typeof cssFont !== 'string') {
    return defaultHeight;
  }

  const sizeFamily = cssFont.match(/([0-9.]+)(px|pt|pc|in|cm|mm|%|em|ex|ch|rem|q)/);

  if (sizeFamily.length !== 3) {
    return defaultHeight;
  }

  switch (sizeFamily[2]) {
    case 'pt':
      return Number(sizeFamily[1]) / 0.75;
    case 'pc':
      return Number(sizeFamily[1]) * 16;
    case 'in':
      return Number(sizeFamily[1]) * 96;
    case 'cm':
      return Number(sizeFamily[1]) * (96.0 / 2.54);
    case 'mm':
      return Number(sizeFamily[1]) * (96.0 / 25.4);
    case '%':
      return Number(sizeFamily[1]) * (defaultHeight / 100 / 0.75);
    case 'em':
    case 'rem':
      return Number(sizeFamily[1]) * (defaultHeight / 0.75);
    case 'q':
      return Number(sizeFamily[1]) * (96 / 25.4 / 4);
    case 'px':
    default:
      return Number(sizeFamily[1]);
  }
}