core-bundle/src/Resources/contao/library/Contao/Image.php
public static function getPixelValue($size)
	{
		@trigger_error('Using Image::getPixelValue() has been deprecated and will no longer work in Contao 5.0.', E_USER_DEPRECATED);

		$value = preg_replace('/[^0-9.-]+/', '', $size);
		$unit = preg_replace('/[^acehimnprtvwx%]/', '', $size);

		// Convert 16px = 1em = 2ex = 12pt = 1pc = 1/6in = 2.54/6cm = 25.4/6mm = 100%
		switch ($unit)
		{
			case '':
			case 'px':
				return (int) round($value);
				break;

			case 'em':
				return (int) round($value * 16);
				break;

			case 'ex':
				return (int) round($value * 16 / 2);
				break;

			case 'pt':
				return (int) round($value * 16 / 12);
				break;

			case 'pc':
				return (int) round($value * 16);
				break;

			case 'in':
				return (int) round($value * 16 * 6);
				break;

			case 'cm':
				return (int) round($value * 16 / (2.54 / 6));
				break;

			case 'mm':
				return (int) round($value * 16 / (25.4 / 6));
				break;

			case '%':
				return (int) round($value * 16 / 100);
				break;
		}

		return 0;
	}
public static function getPixelValue($size)
	{
		@trigger_error('Using Image::getPixelValue() has been deprecated and will no longer work in Contao 5.0.', E_USER_DEPRECATED);

		$value = preg_replace('/[^0-9.-]+/', '', $size);
		$unit = preg_replace('/[^acehimnprtvwx%]/', '', $size);

		// Convert 16px = 1em = 2ex = 12pt = 1pc = 1/6in = 2.54/6cm = 25.4/6mm = 100%
		switch ($unit)
		{
			case '':
			case 'px':
				return (int) round($value);
				break;

			case 'em':
				return (int) round($value * 16);
				break;

			case 'ex':
				return (int) round($value * 16 / 2);
				break;

			case 'pt':
				return (int) round($value * 16 / 12);
				break;

			case 'pc':
				return (int) round($value * 16);
				break;

			case 'in':
				return (int) round($value * 16 * 6);
				break;

			case 'cm':
				return (int) round($value * 16 / (2.54 / 6));
				break;

			case 'mm':
				return (int) round($value * 16 / (25.4 / 6));
				break;

			case '%':
				return (int) round($value * 16 / 100);
				break;
		}

		return 0;
	}
Convert sizes like 2em, 10cm or 12pt to pixels

@param string $size The size string

@return integer The pixel value

@deprecated Deprecated since Contao 4.3, to be removed in Contao 5.0.
Use the contao.image.image_factory service instead.