parseSizeToPx function

double parseSizeToPx(String value, { double fontSizeEmMultiplier = 16.0, double rootFontSizeRemMultiplier = 16.0, })

Converts various CSS units to pixels (px).

This function supports the following units:

• px (pixels)
• cm (centimeters)
• mm (millimeters)
• in (inches)
• pt (points)
• pc (picas)
• em (relative to the font-size of the element)
• rem (relative to the font-size of the root element)

For relative units (em and rem), you need to provide the font-size of the relevant context. The default font-size is 16 pixels.

Example usage:

print(convertToPx('2cm'));  // 75.5905511812
print(convertToPx('10mm')); // 37.7952755906
print(convertToPx('1in'));  // 96.0
print(convertToPx('12pt')); // 16.0
print(convertToPx('1pc'));  // 16.0
print(convertToPx('2em', fontSize: 18.0));  // 36.0
print(convertToPx('2rem', rootFontSize: 20.0));  // 40.0

value is the CSS value to be converted, e.g., '2cm', '10mm', etc. fontSize is the font-size of the current element, used for em units. rootFontSize is the font-size of the root element, used for rem units.

Returns the equivalent value in pixels.

Implementation

double parseSizeToPx(
  String value, {
  double fontSizeEmMultiplier = 16.0,
  double rootFontSizeRemMultiplier = 16.0,
}) {
  // Extract the unit from the value string.
  final unit = value.replaceAll(RegExp(r'[0-9.]'), '');

  // Extract the numeric part of the value string.
  final number =
      double.tryParse(value.replaceAll(RegExp(r'[a-z%]'), '')) ?? 0.0;

  // Convert the numeric value to pixels based on the unit.
  switch (unit) {
    case 'px':
      return number;
    case 'cm':
      return number * cmSizeMultiplier;
    case 'mm':
      return number * mmSizeMultiplier;
    case 'in':
      return number * inchSizeMultiplier;
    case 'pt':
      return number * pointSizeMultiplier;
    case 'pc':
      return number * picasSizeMultiplier;
    case 'em':
      return number * fontSizeEmMultiplier;
    case 'rem':
      return number * rootFontSizeRemMultiplier;
    default:
      throw UnsupportedError('Unit not supported: $unit');
  }
}