Convert a hex, rgba, or rgb color string to Color object in Dart

hexOrRGBToColor.dart

import 'dart:ui';
import 'package:flutter/material.dart';

// Converts a hex, rgb, or rgba color string to Color object. Works with opacity values as well.
// e.g.: 
//       "#000"                    -> Color(0xff000000)
//       "#cc3333"                 -> Color(0xffcc3333)
//       "#cc3333dd"               -> Color(0xddcc3333)
//       "rgb(204, 44, 81)"        -> Color(0xffcc2c51) 
//       "rgba(204, 44, 81, 0.20)" -> Color(0x33cc2c51)
//       "rgba(204, 44, 81, 0.80)" -> Color(0xcccc2c51)
// Check more examples in test.dart

Color hexOrRGBToColor(String colorStr) {
  RegExp hexColorRegex = RegExp(r'^#?([0-9a-fA-F]{3}|[0-9a-fA-F]{6}|[0-9a-fA-F]{8})$');
  if (colorStr.startsWith("rgba")) {
    List rgbaList = colorStr.substring(5, colorStr.length - 1).split(",");
    return Color.fromRGBO(
        int.parse(rgbaList[0]), int.parse(rgbaList[1]), int.parse(rgbaList[2]), double.parse(rgbaList[3]));
  } else if (colorStr.startsWith("rgb")) {
    List rgbList = colorStr.substring(4, colorStr.length - 1).split(",").map((c) => int.parse(c)).toList();
    return Color.fromRGBO(rgbList[0], rgbList[1], rgbList[2], 1.0);
  } else if (hexColorRegex.hasMatch(colorStr)) {
    if (colorStr.length == 4) {
      colorStr = colorStr + colorStr.substring(1, 4);
    }
    if (colorStr.length == 7) {
      int colorValue = int.parse(colorStr.substring(1), radix: 16);
      return Color(colorValue).withOpacity(1.0);
    } else {
      int colorValue = int.parse(colorStr.substring(1, 7), radix: 16);
      double opacityValue = int.parse(colorStr.substring(7), radix: 16).toDouble() / 255;
      return Color(colorValue).withOpacity(opacityValue);
    }
  } else if (colorStr.isEmpty) {
    throw UnsupportedError("Empty color field found.");
  } else if (colorStr == 'none') {
    return Colors.transparent;
  } else {
    throw UnsupportedError("Only hex, rgb, or rgba color format currently supported. String:  $colorStr");
  }
}

test.dart

import 'package:flutter/material.dart';
import 'package:test/test.dart';

void main() {
  group('Hex or RGB string to Color', () {
    test('Can convert hex #cc3333 to Color', () {
      expect(hexOrRGBToColor("#cc3333"), Color(0xffcc3333));
    });
    test('Can convert hex #000 to Color', () {
      expect(hexOrRGBToColor("#000"), Color(0xff000000));
    });
    test('Can convert hex #ffffff to Color', () {
      expect(hexOrRGBToColor("#ffffff"), Color(0xffffffff));
    });
    test('Can convert rgba rgba(255,255,255,0) to Color', () {
      expect(hexOrRGBToColor("rgba(255,255,255,0)"), Color(0x00ffffff));
    });
    test('Can convert rgba rgba(32,33,36,0.55) to Color', () {
      expect(hexOrRGBToColor("rgba(32,33,36,0.55)"), Color(0x8c202124));
    });
    test('Can convert hex #2021248c to Color', () {
      expect(hexOrRGBToColor("#2021248c"), Color(0x8c202124));
    });
    test('Can convert hex #cc2c512e to Color', () {
      expect(hexOrRGBToColor("#cc2c512e"), Color(0x2ecc2c51));
    });
    test('Can convert rgba rgba(204,44, 81, 0.20) to Color', () {
      expect(hexOrRGBToColor("rgba(204,44, 81, 0.20)"), Color(0x33cc2c51));
    });
    test('Can convert rgba rgba(204,44, 81, 0.80) to Color', () {
      expect(hexOrRGBToColor("rgba(204,44, 81, 0.80)"), Color(0xcccc2c51));
    });
    test('Can convert rgb rgb(204,44, 81) to Color', () {
      expect(hexOrRGBToColor("rgb(204,44, 81)"), Color(0xffcc2c51));
    });
    test('Can convert rgb rgb(32,33, 36) to Color', () {
      expect(hexOrRGBToColor("rgb(32,33, 36)"), Color(0xff202124));
    });
}

Thanks a bunch. Appreciate it.