parse static method

Color parse(String s)

Parses a string into a Color.

Accepts rgb() and rgba() colors, in either functional or hex notation, as defined by https://developer.mozilla.org/en/docs/Web/CSS/color_value.

Implementation

// TODO(google) add support for color keywords and hsl.
static Color parse(String s) {
  switch (s[0]) {
    case 'r': // rgb
      final match = _rgbRE.firstMatch(s);
      if (match == null) break;
      final values = match[1]!.split(_separatorRE);
      if (values.length != 3 && values.length != 4) break;
      int color(String s) {
        final last = s.length - 1;
        return s[last] == '%'
            ? 255 * int.parse(s.substring(0, last)) ~/ 100
            : int.parse(s);
      }

      final r = color(values[0]);
      final g = color(values[1]);
      final b = color(values[2]);
      final a = values.length == 4 ? num.parse(values.last) : 1;
      _checkValues(r, g, b, a, s);
      return Color.rgba(r, g, b, a);
    case '#': // hex
      s = s.substring(1);
      // Calculate number of characters per channel.
      final width = s.length == 6 || s.length == 8
          ? 2
          : s.length == 3 || s.length == 4
              ? 1
              : 0;
      if (width == 0) break;
      int hex(int position) {
        final start = position * width;
        final value = int.parse(s.substring(start, start + width), radix: 16);
        return width == 1 ? value * 17 : value;
      }
      final r = hex(0);
      final g = hex(1);
      final b = hex(2);
      final a = s.length % 4 == 0 ? hex(3) / 255 : 1;
      _checkValues(r, g, b, a, s);
      return Color.rgba(r, g, b, a);
  }
  throw FormatException('Invalid color format', s);
}