switched color back to using a hex string

packages/tiled/lib/src/common/color.dart

@@ -5,21 +5,32 @@ part of tiled;
 class ColorData {
   static int _sub(int hex, int index) => (hex >> index * 8) & 0x000000ff;
 
-  final int red;
-  final int green;
-  final int blue;
-  final int alpha;
+  final int _hex;
+
+  int get alpha => _sub(_hex, 3);
+
+  int get red => _sub(_hex, 2);
+
+  int get green => _sub(_hex, 1);
+
+  int get blue => _sub(_hex, 0);
 
   /// Parses the Color from an int using the lower 32-bits and tiled's format: 0xaarrggbb
-  ColorData.hex(int hex)
-      : alpha = _sub(hex, 3),
-        red = _sub(hex, 2),
-        green = _sub(hex, 1),
-        blue = _sub(hex, 0);
+  const ColorData.hex(this._hex);
+
+  const ColorData.rgb(int red, int green, int blue, [int alpha = 255])
+      : assert(red >= 0 && red <= 255),
+        assert(green >= 0 && green <= 255),
+        assert(blue >= 0 && blue <= 255),
+        assert(alpha >= 0 && alpha <= 255),
+        _hex = (alpha << 3 * 8) + (red << 2 * 8) + (green << 1 * 8) +
+            (blue << 0 * 8);
 
-  const ColorData.rgb(this.red, this.green, this.blue, [this.alpha = 255])
+  const ColorData.argb(int alpha, int red, int green, int blue)
       : assert(red >= 0 && red <= 255),
         assert(green >= 0 && green <= 255),
         assert(blue >= 0 && blue <= 255),
-        assert(alpha >= 0 && alpha <= 255);
+        assert(alpha >= 0 && alpha <= 255),
+        _hex = (alpha << 3 * 8) + (red << 2 * 8) + (green << 1 * 8) +
+            (blue << 0 * 8);
 }